i
PTC 30-1 991
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Air Cooled
Heat Exchangers
a
e
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A S I E PTC*30 7 1
O757670 0 8 8 3 2 2 7 T
Air Cooled
Heat.Exchangers
m
PERFORMANCE
TEST
CODES
ASME PTC 30-1991
--``-`-`,,`,,`,`,,`---
AN AMERICAN NATIONAL STANDARD
THE
AMERICA
SN
OCIETY
Engineering
Center
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MECHANICA
E LN G I N E E R S
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ASME P T C x 3 0 71
0757678 0083228 L M
Date of Issuance: May 30,1991
The 1991 edition of this documentis being issued with an automatic addenda
subscription-service. The use of an addenda allows revisions made in response to public review comments or committee actions to be publishedas
necessary; revisions published in addenda will become effective 1 year after
the Date of Issuance of the document. This document will be revised when
the Society approves the issuance of the next edition, scheduled for 1996,
ASME issues written replies to inquiries concerning interpretationof technical
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aspects of this document.The interpretations will be included with theabove
addenda service. Interpretations are not part of the addenda to the document,
ASME is the registered trademark of
The American Society of Mechanical Engineers
This code or standard was developed under proceduresaccredited as meeting tho criteria for
American National Standards. The Consensus Committee that approved the code or standard
was balanced to assure that individuals from competent and concerned interests have had an
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and comment which providesan opportunity for additional'public input from
industry, academia,
regulatory agencies, and the public-at-large.
ASME does not "approve," "rate," or "endorse" any item, construction, proprietary device, or
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ASME does not take any position with respect to the validity of any patent rights asserted in
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No part of this document may be reproduced in any form,
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Copyright O 1991 by
THE AMERICAN SOCIETY OF MECHANICAL ENGINEERS
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Printed in U.S.A.
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ASME P T C * 3 0 91 I0759670 0083229 3
FOREWORD
(This Foreword is not part of ASME PTC 30-1991.)
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In May 1960 the Board on Performance Test Codes organizedPTC 30 on Atmospheric
Cooling Equipment to provide uniform methods and procedures for testing air cooled
heatexchangers,and
the means for interpreting the test results to enable reliable
evaluation .of the performance.capabilityof the equipment. This Committeewas chaired
by Mr. R. T, Mathews, and under his guidance
a preliminary Draft of PTC 30 for Air
Cooled Heat Exchangers was developed. Following the deáth of Chairman Mathews the
Board on Performance Test Codes directedthe reorganization of this Committeein 1977
under the leadership of. interim Chairman Mr. J.C. Westcott. The newly reorganized
committee was entitled PTC 30 on Air Cooled Heat Exchangers. On April 20, 1977 Mr.
C. Westcgtt relinquished the Chair and Mr. J.C. Campbell was elected Chairman.
This Code was approved by the PTC 30 Committee on May 22,1990. It was approved
by the ASME Board on Performance Test Codes and adopted as a standard practice of
the Society on October 5, 1990. It was approved as an American National Standard on
February 15,1991, by theBoard of Standards Reviewof the American National Standards
Institute.
J.
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ASME P T C * 3 O 91 W 0759670 0083230 T W
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this or any other ASME code is a violation ofFederal Law. Legalities aside, the user should
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ASME PTCa30 91 0 Cl959670 0083233 3 9
PERSONNEL OF ASME PERFORMANCE TEST CODE COMMITTEE NO. 30
ON AIR COOLED HEAT EXCHANGERS
(The following is the roster of the Committee at the timeof approval of this Standard.)
OFFICERS
J. C. Campbell, Chairman
R.
B. Miller, Vice Chairman
J. Karian, Secretary
COMMl'lTEE PERSONNEL
J. A. Bartz, Edison Power Research Institute
K. J. Bell, Oklahoma State University
J. M. Burns, Stone and Webster Engineering Corp.
J. C. Campbell, Lilie-Hoffman Cooling Towers, Inc. (retired)
R. R. Carpenter, Duke Power Co.
M. C. Hu, United Engineers and Constructors, Inc.
B. M; Johnson, Battelle Northwest
G. E. Kluppel, Hudson Products Corp.
P. A. Lindahl, The Marley Cooling Tower Co.
P. M. McHale, Ebasco Plant Services Inc.
R. B. Miller, Stone and Webster Engineering Corp.
D. S. Parris, Jr., American Energy
J. G. Yost, Environmental Systems Corp.
V
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A S I EP T C * 3 O
91
m
0759670 0083232 3 111
BOARD ON PERFORMANCE TEST CODES PERSONNEL
J. S. Davis, Jr., Vice President
N. R. Derning, Vice Chairman
W. O. Hays, Secretary
P. M. Gerhart
R. Jorgensen
D. R, Keyser
W. G. McLean
G. H.
Mittendorf, Jr.
J. W. Murdock
S. P. Nuspl
R. P. Perkins
R. W. Perry
A. L, Plurnley
C. B. Scharp
J. W. Siegmund
R. E. Sommerlad
J. C. Westcott
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.
A. F. Armor
R. L. Bannister
R. J. Biese
J. A. Booth
B. Bornstein
H. G. Crim
G. J. Gerber
vi
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CONTENTS
...............................................................................
.....................................................................
Foreword
Committee Roster
O
1
2
3
....................................................................
Object and
Scope
..............................................................
1.1 Object ......................................................................
1.2 Scope ......................................................................
I .3 Urrcertainty .................................................................
DefinitionsandDescription of Terms
........................................
2.1 Terms ......................................................................
2.2
Letter
Symbols
.............................................................
Guiding
Principles
.............................................................
3.1
General .....................................................................
3.2 AgreementsPrior to Test ..................................................
3.3 Selection of Personnel .....................................................
3.4 Pre-Test Uncertainty Analysis .............................................
3.5 Arrangement of TestApparatus ...........................................
3.6 Methods of Operation During Testing ....................................
3.7 Provisions tor EquipmentInspection ......................................
3.8 Calibration of Instruments .................................................
3.9 Preliminary
Testing ........................................................
3.10 Conduct of Test ............................................................
Introduction
...
111
V
1
3
3
3
3
5
5
8
11
11
11
11
11
11
12
12
12
12
13
..............................................................
...........................................................
.................................................
.....................................
.................................
.........................
............................................
InstrumentsandMethods of Measurement ..................................
4.1
General .....................................................................
4.2 Measurement of PhysicalDimensions ....................................
4.3 Fan
Measurements
........................................................
3.12
3.J 3
3.14
3.1 5
3.16
3.1 7
4
Procedures
Duration of Test
Number of TestReadings
Permissible Lirnitsof TestParameters
Degree of Constancy of Test Conditions
Causes for Rejection of Test Readings or Results
Post-Test Uncertainty Analysis
................................................
...........................
.......................................
4.4Measurement
of Air Flow.,
4.5
Measurement of Air-SidePressure Differential
4.6 Measurement of Fan Driver Power
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13
13
13
13
14
14
14
15
15
15
15
15
17
18
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3.1 1 Permissible and Nonpermissible Adjustments to Test
Measurement ofSoundLevel
Measurement of AtmosphericPressure
Measurement ofEnvironmentalEffects
...................................
Measurement of Wind Velocity
Measurement of Air Temperatures
Measurement of Ambient and Entering Air Temperatures
Measurement ofExit Air Temperature
Measurement of Process Fluid Temperatures
Measurement of Process Fluid Pressures
Measurement of Process Fluid. Flow Rate
.c
Measurement of Composition of Process Fluid
5.5
Computation of
Effective
Mean
Temperature
Difference
Computation of OverallHeatTransferCoefficient
Determination ofAir-SidePressureLosses
Determination of Process Fluid PressureLosses
Adjustments of TestData to DesignConditions
...................................
...........................................
........................................
...............
....................................
............................
.................................
........ .......................
..........................
Computation of Results ........................................................
5.1
General .....................................................................
5.2
ReviewofTestDataandTestConditions
.................................
5.3
Reduction of TestData ....................................................
5.4
Determination of MaterialandHeatBalances
............................
5
...............................................................
.......................
...............................
..........................
..........................
Report of Results ...............................................................
6.1
Composition of Report .....................................................
6.2
Report
Data ................................................................
5.6
5.7
5.8
5.9
6
.............................................
4.7
4.8
4.9
4.10
4.1 1
4.12
4J3
4.14
4.1 5
4.1 6
4.1 7
19
19
19
19
19
20
20
20
20
21
21
23
23
23
23
24
25
25
26
26
28
47
,
.
47
48
Figures
4.1 Location of Air Velocity and Temperature Measurement
4.2
5.1
.
5.2
5.3
5.4
5.5
5.6
t
5.7
5.8
5.9
5.10
5.1 l
5.12
5.13
........................................................
.................................
...............................................
Points Across Fan Ring
Typical Velocity Distribution Across Fan Stack
Mean Temperature Difference Relationships - Crossflow
Unit .- 1 TubeRow,Unmixed
Mean. Temperature Difference Relationships- Crossflow
Unit 2 TubeRows, 1 Pass.Unmixed
Mean Temperature Difference Relationships - Crossflow
Unit - 3 TubeRows, 1 Pass,Unmixed
Mean Temperature Difference Relationships - Crossflow
Unit - 4 TubeRows; 1 Pass,Unmixed
Mean Temperature Difference Relationships - Crossflow
.Unit 2 Tube Rows, 2 Passes, Unmixed Between Passes
Mean Temperature Difference Relationships - Crossflow
Unit - 3 TubeRows, 3 Passes, Unmixed Between Passes
Mean Temperature Difference Relationships- Crossflow
Unit - 4 Tube Rows. 4 Passes. Unmixed Between Passes .................
Mean Temperature Difference Relationships - -Crossflow
Unit - 4 Tube Rows in 2 Passes, 2 Tube Rows per Pass,
Mixed at the Header
Schematic of Process Fluid Piping .............................................
Fin Efficiency of Several Types of Straight Fins
Efficiency Curves for Four Types of Spine Fins
Efficiency of Annular Fins of Constant Thickness
Efficiency of Annular Fins With Constant Metal Area for
i
Heat Flow
.....................................
-
.....................................
.....................................
.................
.................
-
.........................................................
................................
................................
..............................
.................................. .................................
m
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viii
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18
33
34
35
36
37
38
39
40
41
42
43
44
45
- A S I E P T C * I O 91
0759670 0083238 4
Tables
4.1Recommended
Minimum Number of Air Velocity
MeasurementPoints for FanRingTraverse
5.1Values
of Fu for Equation5.38
.................................
.................................................
.
Appendices
..............................................................
.........................................................................
..................................................
........................................................................
..........................................................................
77
..............................................................
......................................................................
Testing
A Guidelines
B
Example
C
Example Uncertainty Analysis
-D
SpecialConsiderations for Computation andAdjustment of
Results
E
Fouling
F
Recirculation of Air
G
References
17
31
49
51
57
65
79
81
Figures
R.1 Moody-Darcy Friction Factor Chart for Flow Through Plain
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.........................................................................
.........................................................................
.
....................
Tubes
D. 2a Chart for Calculating In-Tube Heat
Transfer Coefficients for
Water
D.2b Correction Factor to Fig D.2a for Other Tube Diameters
D.3Two-Phase
Flow Friction Pressure Drop Correction Factor
D.4 ß as a Function for JI ,. for the Chaddock Method
D.5 Colburn Correlation for Condensation on a Vertical.Surface
No VaporShear
-
Tables
...................
............................
...........................................................
....................................
....................................
...........................................
...........................................
..............................................................
C.1 aSensitivityFactorsforUncertaintyAnalysis
C.l b Sensitivity Factors for. Uncertainty Analysis
C.2 Error
Estimate
ValueS.for
Capability
C.3 . ErrorEstimateValues for Capability
C.4 Two-Tailed STUDENT-t
Table
for the 95
Percent
Confidence
Level
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‘ASME P T C 8 3 0 91
0759670
0083237
2
.
ASME PTC 30-1991
ASME PERFORMANCE TEST CODES
Code on
AIR COOLED HEAT EXCHANGERS
- INTRODUCTION
This Code provides instructions for the testing of
air cooled heat exchangers. The equipment,
as herein
defined, refers to apparatus for the transfer of heat
from process fluids to atmospheric air.
The testing methods described in this Code will
yield results of accuracy consistent with current engineering knowledge and practice.
The purpose of this Code is to provide standard
directions and rules for the conduct and report of
performance testson air cooled heat exchangers and
the measurement and evaluationof relevant data.
This Code is a voluntary standard; adherenceto it
depends on prior mutual’agreementof all parties involved in the performancetesting of specificair
cooled heat exchangers.
Unless otherwise specified, all references herein
to
ofher codes refer to ASME Performance Test Codes.
Terms used but not defined herein are defined in the
Code on Definitions and Values
(PTC 2 ) . Descriptions
of instruments and apparatus, beyond those specified
and describedin this Code, but necessaryto conduct
the tests, may be found in the Supplements on Instruments and Apparatus (PTC 19 Series).
When using this Code,a careful study should first
be made of the most recent issuesof Codes on Genand Definitions and Values
eral Instructions (PTC I),
(PTC 21, togetherwithall other codes referred to
herein. In the event of any discrepancies between
specificdirectionscontainedherein,andthose
in
codesincorporated by reference,thisCodeshall
govern.
1
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SECTION O
ASME P T C * 3 0 71
m
0757670 0083235 7
m
ASME PTC 30-1991
AIR COOLED HEAT EXCHANGERS
SECTION 1
OBJECT AND SCOPE
presented. Such modifications shall be agreed bythe
parties to the test.
The objectof this Code is
to provide uniform methThe scope of this Code also includes, directly or
ods and procedures for testing the thermodynamic
by reference, recommended methods for obtaining
and fluid mechanical performanceof air cooled heat
data,measurements,observations,andsamples
to
exchangers, and for calculating adjustments to the
determine the following:
test results to design conditions for comparison with
(a) PhysicalDimensions
the guarantee as defined in para. 5.9.4.
(b) Air FlowRate
Excluded from the scope of this Code are evapo(c) Air-Side Pressure Differential
rativetypecoolers(wetcoolingtowers),andany
(d) FanDriverPower
cooling equipment which combines evaporative and
(e) SoundLevel
convective air cooling (wet/dry type).
(0 Atmospheric Pressure
This Code does apply
to wet/dry type heat exchan@ EnvironmentalEffects
gers when, by mutual agreement,
the heat exchanger
(h) Wind Velocity
can be operated and tested as a dry type unit.
(i) Air Temperatures
0) Entering Air Temperature
(k) Exit Air Temperature
(I) Process Fluid Temperatures
1.2 SCOPE
(m) Process Fluid Pressures
The scope of this Code covers, but is not limited
(n) Process Fluid FlowRate
to, the testing of mechanical draft heat exchangers,
(o) Composition of Process Fluid
of both the forced draft and induced draft types; nat(o) Percent Capability
ural draft heat exchangers; and fan assisted natural
(9) Process Fluid Pressure Drop
draft heat exchangers.
From a heat transfer surface standpoint, this Code
covers all tube bundle orientations, including: verti1.3 UNCERTAINTY
cal, horizontal, and slanted conduit heat exchangers.
In keeping with the philosophy of the Code, the
Both bare surfaces and finned surfaces
are included
best
.available technical information has been used
in
as conduit type heat exchanger components. While
developing
the
recommended
instrumentation
and
conventional round tubes with circular fins are asprocedures to provide the highest level of testing acsumed in this Code, the procedures can be modified
curacy.Everymeasurementhas
someuncertainty;
by mutual agreement to apply to other surface contherefore,
so
do
the
test
results.
Any
departure from
figurations.
Code
recommendations
could
introduce
additional'
While the cooling fluid is restricted to atmospheric
in
the
measurements
beyond
that considuncertainty
air, the tube-side fluid can be any chemical element,
of
a
Code test.
ered
acceptable
to
meet
the
objectives
compound or mixture, in single-phase flow, liquid or
The expected uncertainty level(s) of tests run in acgas, or in two-phase flow.
cordance with this Code, based on estimates of preThis Code is written under
the assumption thatthe
cision and bias errors
of the specified instrumentation
Air Cooled Heat Exchanger (ACHE) may betested as
and procedures, is f two to five percent.
having a discrete process stream or that only one
Users of the Code shall determinethe quality of a
process fluid stream is being investigated. In other
Code test for the specified equipment being tested
cases, modifications must be made
to the procedures
1.1 OBJECT
3
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ASME P T C 8 3 0 91
m 0759670 0083236 O m
AIR COOLED HEAT EXCHANGERS
ASME PTC 30-1991
by performing pre-test
and post-test uncertainty analyses. If either of these indicates uncertainty exceeding
& five percent, the test shall not be deemed a Code
test.
An example of the magnitude of the uncertaintyin
individual measurements and the manner in which
individual uncertainties are
combinedto obtain overall test uncertaintyof final results is included in Appendix Cfor a typical jacket-water cooler.
Test results shall be reported as calculated from
test observations, with only such corrections as are
provided in this Code. Uncertainties are not to be
used to alter testresults.
TheSupplement
on Measurement Uncertainty
(PTC 19.1) provides additional information on combining types of errors into an overall test uncertainty.
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ASME PTC 30-1991
AIR COOLED HEAT EXCHANGERS
SECTtON 2
DEFINtTtONS AND
DESCRIPTION OF TERMS
a
2.1 TERMS
In this Section only those terms are defined which
are characteristic of air cooled heat exchangers and
the requirements for testing them.For the definition
of all other physical terms, or the description of instruments usedin this Code, reference is made
to the
literature and to PTC 19 Series on Instruments and
Apparatus.
Term
Description
Adjusted Value
A value adjustedfrom test conditions to design conditions.
Air
Mixture ofgases and associated water vapor around the earth; dry air plus its
associated water vapor. This term is used synonymouslywith atmosphere or
moist air.
Air Cooled Heat
Exchanger
(ACHË)
A heat exchanger utilizing air as the heat sink to absorb heat from a closed circuit
process fluid. This term is used synonymously with dry cooling tower in the
power industry,
Air, Dry
Reference to the dry gas portion of air.
Air Flow Rate
The mass per unit time ofair flodng through the ACHE.
Air, Standard
Dry air at standard temperature (70"F) and pressure (14.696 psia) which has a
density of approximately 0.075 IbdfF.
Alternate Process
Fluid
A fluid selected for use in performance testing when use of the actual design fluid
is impractical for testing purposes dueto proprietary.or other reasons.
Ambient Air
Temperature
The temperature of the air measured upwind of the ACHE within its air supply
stream.
Ambient Wind
Velocity
The speed and direction of the wind measured upwind of the ACHE within its air
supply stream.
Approach
Temperature
Difference
The minimum temperature difference betweenthe process stream and air stream
at an exiting condition:
'(a) r2-tl (counterflow)
or, (b) Tl -t2 (counterflow)
or, (c) T2-t2 (cocurrent flow or cross flow)
5
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ASME P T C * 3 O 91
0759670 0083240 2
m
AIR COOLED HEAT EXCHANGERS
ASME PTC 30-1991
Term
Description
Aspect Ratio
The ratio of certain key dimensionsthat establishes similarity of shape or
proportionality
Atmospheric
Pressure
The pressure of the atmosphere at the location of the ACHE. .
Bare Surface
The surface areaof the bare conduit excluding extended surface.-This termis
used synonymouslywith prime surface.
Bundle
Assembly of headers, tubes (conduits), tube supports and side frames.
Calibration
Establishment of a correction basis for an instrument by comparison to an
acceptable reference standard. (See PTC 19 Series).
Capability
in terms of test capacity, that is, the
Thermal performance capability expressed
actual quantity of process fluid the ACHE will handle at design conditions of fluid
inlet and outlet temperatures, fluid inlet pressure, fluid composition, air inlet
temperature and fan power.
Design Values
Performance conditions upon which the designof the ACHE was guaranteed.
Drive Train
Mechanical
Efficiency
The fraction of the driver output power whichis transmitted to the fan.
EnteringAir
Temperature
The temperatureof the air enteringthe ACHE.
Exit Air
Temperature
The temperature of the air leavingthe ACHE.
Extended Surface
Surface area added to the bare surface.
Face Area
The gross airflow area through the ACHE heat transfer surfacein a plane normal
to the air flow.
Fan Assisted
Natural Draft
A type of ACHE utilizing a combination of chimney effect and fan(s)to provide
Fan Input Power
The power which is actually transmitted to the fan.
Fan Pitch
The angle from the fan plane atthe designated pitch measurementlocation to
which the bladesof a fan are set.
Fan Speed
The number of fan revolutions per unit time.
Fin Efficiency
The ratio of the total heat dissipatedby the fin tothat which would bedissipated
if the entire fin surface were atthe temperature of the fin root.
Finned Surface,
Inside
The contact surface exposedto the process fluid. This term is used synonymously
with inside extendedsurface.
Finned Surface,
Outside
The contact surface exposedto the air flow. This term is used synonymously with
outside extendedsurface.
Flow Regime
A fluid mechanics definition of flow characteristics, e.g., laminar Or tUfbUlent flow.
the required air flow.
6
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One or more tube bundlesserved by one or more fans complete with structure,
plenum, and other attendant equipment. This term is used synonymouslywith
cell.
8
e
a
ASME PTCs30 73 W 0757670 0083243 4 U
AIR COOLED HEAT EXCHANGERS
ASME PTC 30-1991
Term
Description
Forced Draft
A type of mechanical draft ACHEin which the fan is located in the air current
upstream from ttie heat exchanger surface.
Fouling
Accumulated foreign material suchas corrosion products or any other deposits on
the heat transfer surface.
Free Flow Area
The minimum air flow area through the ACHE heat transfer surfacein a plane
normal to the air flow.
Induced Draft
A type of mechanical draft ACHE in which the fan is located in the air current
downstream from the heat exchanger surface.
Initial
Temperature
Difference
Temperature difference between entering process temperature and entering air
temperature, T, 4 , .
Interference
Disturbance of the performance of an ACHE caused by an external heat sourceor
obstruction.
Mechanical Draft
A type of ACHE in which the airflow is maintained by mechanical air moving
devices such as fans or blowers.
Motor Output
Power
The net power delivered by the motor outputshaft.
Natural Draft
A type of ACHE in which the air flow is maintained by the difference in the
densities of the ambient air andthe exiting air streams.
Prime Surface
The-surface areaof the bare conduit excluding extended
surface. This term is
used synonymouslywith baie surface.
Process Fluid
The fluid circulated within the closed conduitof an ACHE.
Process Fluid
Temperature
Generally, an average bulk temperature of the process fluid defined at some
location entering, leaving, pr within the ACHE.
Process Fluid
Temperature
Range
The difference between inlet and outlet temperatures of the process fluid.
Process Fluid
Pressure Drop
The total hydraulic loss, including dynamic and static (if applicable) losses,
between defined locationsas the process fluid enters and leavesthe ACHE.
Process Fluid
Flow Rate
.
The mass per unit time of process fluid flowing through the ACHE.
Recirculation
The flow ofexit air into the ACHE air inlet.
Test Run
A complete set of data that w i l l allow analysisof capability per this Code. In some
cases multiple test runs are taken and averagedto yield the capability.
Test Uncertainty
The overall uncertainty in results dueto the combined effects of instrument
inaccurcy, unsteady state conditions, and reading and methodological error.
Test Value
A value measured during a test with its calibration correction applied.
Tube Row
All of the tubes or conduits within an ACHE which have axial centerlinesfalling
within a plane normal to the air flow. This term is synonymous to tube /aver.
Unit
One or more tube bundlesin one or more bays for an individual service.
7
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ASME P T C U 3 0 91 W 0759670 0 8 8 3 P 4 2 b H
ASME PTC 30-1991
2.2
AIR COOLED HEAT EXCHANGERS
LETTER SYMBOLS
Symbols that do not conform with this list will be
defined in thetextimmediately
following their
usage. Numerical constantsused in theequations
andexamples in the Code,unless otherwise specified, are based on US. Customary Units.
Symbol
Definition
Dimensions
SI Units
U.S. Customary Units
A
Heat transfer surface area
ft=
ACFM
Actual cubic feet per minute
ft3/min
B
Barometric pressure
in. Hg Abs.
Pa
BWG
Birmingham wire gage, a unit for
measurement of thickness
Dimensionless
Dimensionless
C
,
Specific heat at constant pressure
Btu/lbm.OF
J/kg°C
C"
Specific heat at constant volume
BtuAbm"F
J/kg°C
d
Wall thickness
ft
m
D
Diameter
ft
m
D.¶
Equivalent diameter, 4Sl /Zl and 4S0 lZe
ft
m
DBT
Dry-bulb temperature
"F
"C
E
Elevation above mean sea level
ft
m
EMTD
Effective mean temperature difference
"F
"C
F
Temperature correction factor equal to
EMTDILMTD
Dimensionless
Dimensionless
fM
Friction factor
Dimensionless
Dimensionless
t;
Fin thickness
ft
m
g
Acceleration dueto gravity
ftlsec'
m/SZ
gc
Proportionality factor in
Newton's 2nd Law
G.
Mass veloclty, W& and WIS,
Ibm/hr*ft2
h
Coeffdent of-heattransfer
Btu/hr.ft2*"F
hP
Fan driver output power
hP
H
Enthalpy
BtuAbm
HL
Gtent heat of vaporization of process fluid
Btu/lbm
iTD
Initial temperature
difference,
k
Thermal conductivity
Btu/hrft*"F
I
Fin height
ft
L
Length
ft
.
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mz
32.18 Ibmft
Ibfssecl
(T, -t,)
"F
8
Not for Resale
1 kgm
N*s2
k&mZ
*
W/m2-"C
W
--``-`-`,,`,,`,`,,`---
.
LED
AIR
HEAT EXCHANGERS
ASME PTC 30-1991
Dimensions
Symbol
Definltion
U.S. Customary Units
SI Units
LMTD
Log mean temperature difference
"F
"C
N
Number of tubes
Dimensionless
Dimensionless
N
Number of measurements
Dimensionless
Dimensionless
Nh
Number of fins per unit length
ft-1
m-'
Nm
Fan speed
RPM
rPs
NTU
Number of transfer units
Dimensionless
Dimensionless
Nu
Nusselt number, bD/k
Dimensionless
Dimensionless
P
Air
pressure
Ibf/ft2
Pa
P
Thermal effectiveness,
Dimensionless
Dimensionless
P
Process stream pressure
Ibf/fta
Pa
Pr
Prandtl number, c, IJk
Dimensionless
Dimensionless
Q
Heattransferrate
Btuhr
W
r
Radius
ft
m
R
Temperature difference ratio equal to
Dimensionless
Dimensionless
hrft*."F/Btu
m2.'CIW
(TI -T&
'
.
(i2-tJ/fll
-tJ
.
-4)
R
Thermal resistance
RH
Hydraulic radius
. f t
m
R,
Gas constant of air
53.32 ft-lbf/lbm."R
286.9 JkgK
Re
Reynolds number, GD/&
Dimensionless
RPM
Rotational speed
Revolutions per
minute
s
Net clear distance betweenfins
ft
m
s
Cross sectional flow area
ft2
m2
SCFM
Standardcubicfeetper minute measuredat
70°F and 14.696 psia, dry air
st
Nu
Stanton number, b/c,G = RePr
Dimensionless
t
Air temperature
"F
T
Process fluid temperature
OF
Tg
Torque
Ibf-ft
U
Overall heat transfercoefficient
Btuhr.ft2."F
V
Speed
Wmin
W
Air flow rate
Ibtnhr
ft3/min
9
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Dimensionless
ASME P T C * 3 B 91
0757670 8083244
ASME PTC 30-1991
Symbol
AIR COOLED HEAT EXCHANGERS
--``-`-`,,`,,`,`,,`---
Definition
Dimensions
U.S. Customary Units
SI Units
Process fluid flow rate
Ibm/hr
kds
Wet-bulb temperature
"F
"C
Flow area wetted perimeter
ft
m
Summation
Dimensionless
Dimensionless
Density
Ibm/ft3
kdm3
Efficiency
Dimensionless
Dimensionless
Thermal effectiveness
Dimensionless
Dimensionless
Fin efficiency
Dimensionless
Dimensionless
Two phase flow multiplier
Dimensionless
Dimensionless
Differential
Dimensionless
Dimensionless
viscosity
Ibmihr4t
kgkm
Subscript
a
af
b
d
d
e
f
fn
R
,
r
s
T
V'
Description
Air
Air film
Bond
Dirt
Dry
Electrical
Fouling
Fin
Hydraulic
Inside
Liquid
Mechanical
Moist
Outside
Prime tube
Process
Absolute
temperature
Fin root wall
Reference surface
Static
Total
Vapor
V
Velocity
W
Wall
Zone
Inlet
Outlet
Z
1
2
Superscript
*
o
f
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T
Description
Design value
Test value
Adiusted value
10
Not for Resale
AIR COOLED HEAT EXCHANGERS
o
@
@
@
GUIDING PRINCIPLES
3.1 GENERAL
.
Theperformance of atmospheric cooling equipmentisinfluencedby the conditions of the atmosphere in whichitoperates.This.Coderequires
recognition of the fact that changes in the ambient
and other operating conditionswill affect the equipment performance. Extraneous sources of heat and
those variables which affectthe air flow must be recorded and evaluated. It is extremely important that
performance tests be conducted under stable operating conditions,
3.2 AGREEMENTSPRIOR TO TEST
Theparties to any testunderthisCodeshallreach
definite agreement'on the specific objective of the
test and the method of operation. This shall reflect
the intent of any applicable contract or specification.
Contractualtermsshallbeagreed
to concerning
treatment of uncertaintyrelative to acceptance ofequipment based on reported capability. Any specifiedorcontractoperatingconditions,and/orany
specified performance conditions that are pertinent
to the objectives of the test, shall be ascertained.
Any
omissions or ambiguitiesas to any of the conditions
are to be eliminated or their values or intent agreed
uponbefore the test is started.
The parties to the test shall reach agreement, prior
to the start of test, regarding the following items:
(a) the specific methods and scope of inspection
prior to and during the test;
Ib) the number of test runs and reading intervals;
(c) the method for startingthe test;
(d) the method of operation of the equipment;
(e) the fan. blade settings;
(f) the type, quantity, calibration, and location of
all instruments;
(g, the allowable bias in instrumentation and measurements, andthe maximum permissible overalluncertainty in the test results (see Appendix Cfor
discussion);
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(h) the procedures and frequency for cleaningthe
air- and/or tube-side surfaces;
(i) the scope of the test beyond.this Code, including partial testing or any other departures from this
Code;
ci, the fouling factorsto be assumed for analysisof
results (see AppendixE).
3.3 SELECTION OF PERSONNEL
The test shall be conducted by, or under the supervision of, personnel fully experienced in plant and
equipment operating procedures.The test procedure
shall conform to the latest requirementsof all applicable industry, local, state, and Federal regulations.
Testing an air cooled heat exchanger presents potentially hazardous conditions which may include rotating equipment, high temperatures, hazardous fluids,
noise, and danger of falling.
3.4 PRE-TESTUNCERTAINTYANALYSIS
Prior to the test an uncertainty analysis shall be
performed. An example of uncertainty analysis isincluded in Appendix C. Theanalysisisbeneficial in
that it will highlight those parameters that are major
contributors to test uncertainty.
Parties to the test shall add or improve instrumentation or increase the frequency of readings if such
actions will materially improve test accuracy.
3.5 ARRANGEMENT OF TEST APPARATUS
The performance test shall be conducted with all
components of the ACHE oriented as specified for
normal operation. Any changes from normal operation or orientation shall be agreed priorto the test.
Not for Resale
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SECTION 3
ASME PTC 30-1991
ASME P T C * 3 0 71 .P 0757670 O083246 3
--``-`-`,,`,,`,`,,`---
AIR COOLED HEAT EXCHANGERS
ASME PTC 30-1991
3.6 METHODS OF OPERATION DURING
. TESTING
Although it is preferable to evaluate the-performance of air cooled heat exchangers under complete
i normally
design and steady-state conditions, this s
not practicablefor an on-site evaluationof this equipment. Therefore, prior agreement shall be established
for procedures to adjust the test results
to the design
conditions as in para. 5.9.
3.7 PROVISIONS FOR EQUIPMENT INSPECTION
3.9 PRELIMINARYTESTING
The information in para. 1.2 should be used as a
guide in examination of the equipment prior to and
during the test, with special attention to the foll0.wing.
(i$ Examine the general condition, as it affects the
thermal performance and air flow.
(b) External heat transfer surfaces shall be.essen-.
tially free of scale, dirt, oil, and other foreign debris
that would affect the.heat transfer and obstruct the
air flow. If the need is established, the unit shall be
cleaned by commercially acceptable methods.
(c) Internal heat transfer surfaces and headers shall
be essentially clean-andfree of scale, rust, dirt, and
other foreignmatter. i f the need is established, these
surfaces shall be cleaned
by commercially acceptable
methods.
(d) Mechanical equipment shall be in good working order, and checked for freedom of movement.
Fansshall be checked for. properrotation,blade
pitch, speed, and tip clearance.
Provision shallbe .made to ascertain that all equipment and instru’ments are
in good working order, free
from defects and obstructions, and accessible, as required for repair,replacement,andobservation.
In
the event the equipment is not in satisfactory oper~
Prior to the test, the parties to the test shall reach
agreement on the calibration procedures to be followed. Supplements on Instruments and Apparatus
(PTC 1.9 Series) may be used as a guide for the selection,use,and calibration of instruments. Instrui
ment calibrations and correction curves should be
prepared in advance.
Removal and replacement
of any instrument during
the test may require calib!ation of the new instrument
prior to continuing the test. All calibration curves
shall be retained
as part of the permanenttest record.
ating
condition,
such
adjustments
or changes as may
be required to place it in proper operatingcondition
shallbemade.However,
no adjustmentsshallbe
made which are not practical in continuous commercial operation.
3.8 CALIBRATIONOFINSTRUMENTS
All instruments to be used in the test shall be calibrated prior to the test. If the accuracy of any instrument is questionable during the test it shall also be
calibrated after the test.
Preliminary or partial testingto evaluate certain aspects of the heat exchangerperformance may be considered when a complete set of data is not required
or is not applicable. This may.includethe following.
3.9.1 Testing at Factory for
Air
Flow,
Fan
Performance, Sound level, or Vibration. Complete
air flow and fan performancetests can be conducted
at the factory and results adjusted to design conditions. Vibration and sound level measurements can
be obtained to ensuremechanicalperformance
within specification requirement.
3.9.2 Testing at Factory for Process-Side Pressure
Drop. Design fluids can be circulated through the
heat exchanger and pressure drop measured and results adjusted to design conditions.
3.9.3 Substitute Fluid Testing. Substitute fluid testing may be donefor many reasons suchas when the
description of the process fluid is considered confidential or proprietary, when the processfluid is hazardous, or when economically justified. Substitute
fluid testing is characterized by the
use of fluids readily available,safe,andeasilyhandled,andwhose
physical properties provide usable experimental data
acceptable to both parties. The performance of an
exchanger can be calculated from test data with a
substitute fluid by the use of this Code. The adjustment of the test results, usingthe substitute-fluid,to
design conditions.withthe design processfluid is beyond thescope of this Code. When a substitute
fluid
is to be used for this purpose, it is suggested that a
qualified consultant be retainedto advise the parties
to the contract, prior to purchase of the equipment,
on the proper method of testing and interpretation
of results.
12
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ASME PTC 30-1991
AIR COOLED HEAT EXCHANGERS
.of runs and the frequency of readings shall be determined by mutual agreement priorto the test.
Prior to the test, the equipment shall be operated
longenough to establishsteady-stateconditions
which are within permissible limits. No adjustments
should be made to the equipment, or test procedures, which are not consistent with normal operation.The test shouldnotbe run if rain,snow,or
severe.wind conditionsare present.
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0
3.14 PERMISSIBLELIMITS OF TESTPARAMETERS
Performance tests shall be conducted within the
following limitations'.
(a) Testsshallbemadeduringperiods
of stable
weather, not subject to rapid changes in air temperature, rain, snow, or high wind conditions.
Cb) Average wind speed shall not exceed 10 mph
wifh one minuteaveragesnot to exceed 15 mph.
Wind direction and shift shall be within contractual
by the paragreement unless otherwise agreed upon
ties to the test.
(c) Entering dry-bulb temperatureshallbenot
more than 10°F aboveor 40°F below designdry-bulb
temperature. The average change shall not exceed
59F per hour.
3.1 1PERMISSIBLE AND NONPERMISSIBLE
ADJUSTMENTS TO TEST PROCEDURES
No changesoradjustments to the test procedures
all parties tò the test agree.
shallbemadeunless
These adjustments might include a change in test
conditions, a change in the arrangement of components of test, a change in instrumentation, a change
in fan blade settings, a change in test schedule or
number of readings required.
Once the test has started no manual changes or
adjustments in the process fluid flow rate or air moving equipment shall be made.If permissible limits of
test parametershavebeenexceeded,adjustments
and changes may be made by mutual agreement of
the parties to the test,and the test restartedwhen
equilibrium has been reestablished.
NOTE: It must be recognized that the pour point or viscosity of
the process fluid
ran governthe lower limit. Unless auxiliary equipment is provided to modify inlet air temperature, the lower entering air temperature limit shall not be less than 10°F above the
process fluid pour point.
(o') The air flow shall be within+: 1O percent of the
design value.
(e) Procêss fluid flow rate shall be within2 15 percent of the design value, and shall not vary by more
than 5 percent duringthe test.
(19 Process fluid inlet and outlet temperatures shall
be within k1O"F of the design values, and shall not
vary by more than 4°F during the test.
@ The process fluid temperature range shall be.
within +.10 percent of the design value, and shall not
vary by more than 5 percent duringthe test.
Ch) For cooling gases or condensing vapors
at pressures above atmospheric pressure, the process fluid
inlet pressure shall be within
4 10 percent of the
or condensing vapors
design value. For cooling gases
below atmospheric pressure, the parties to the test
should agree to an acceptable pressure priorto conducting the test. For cooling liquids, any pressureup
to the des.@ pressure of the ACHE is acceptable;
however, the pressure should not so
below that there
is possibility of vaporization or degassing. The process fluid inlet pressure shall not vary by more than
10 percent duringthe test.
li) Heat duty shall be within 2 2 0 percent of the
design value.
3.12 DURATION OF TEST
0
0
Each test run shallbeconducted in accordance
with the predetermined schedule which fixes itsduration, taking into account the instrumentation and
number of observers available andthe number of simultaneous readings that can be assigned without
affecting the accuracy .of the test. Inspection of the
data from each test run should be made before terminatingthe run, so that any inconsistencies in the
observed data may be detected and corrected.If valid
corrections- cannot be made, the test run shallbe
repeated.
Data shall be recorded for sufficient time
to ensure
a select periodof at least one hour duringwhich-the
provisions of paras. 3.13 through 3.16 are satisfied.
3.13 NUMBER OF TESTREADINGS
All instrument readings required
by this Code shall
be taken after reaching steady-state process conditions. The number of readings per run will depend
on the method of data aquisition, expected test uncertainty, andthe size of the equipment. The number
'If any oneof these limitations conflict
with the basis of guarantee,
these do not apply.
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ASME PTCx30 Si 0759670
0083248 7
m
AIR COOLED HEAT EXCHANGERS
ASME PTC 30-1991
(d) equipment or instrumentation failures, improper operation, wrong adjustments, or poor calibrations;
Since the test of an ACHE may occur over an ex(e) poor test operating conditions resulting in extended period, each test run shall be separately concessive sound or vibration, low temperature differtrolled to achieve steady-stateconditions using fixed
entials, condensate flooding, poor flow distribution,
fan pitch, fan speed,and air flow control settings.
or air leakage;
Thus, each test run may be made atdifferent steady(19 post-test uncertainty analysis indicating uncerstateoperatingconditions during theperiod of a
tainty of test results exceedingfive percent;
complete. performance test. Variations of operating
heatbalancediscrepancycalculated
by Eq.
parameters throughout the entire performance test
(5.8) greater than 15 percent. If this occurs, an inshall be maintained as low as practicable, but must
vestigation of the equipment and instrumentation
be maintained within the limits delineated in para.
should be madeto determine the cause for this dis3.14. Since the actual operating conditionswill vary
crepancy, and the test repeated.
somewhat from the specific design conditions for the
All of the above factors shallbe evaluated prior to
equipment, the test results must be adjusted
to equivand/or
during the test to ascertain their effects on the
alent designconditions by the methodshown in para.
system
performance. The testshould be deferred un5.9.
til satisfactory conditions existwhich will enable accurate data to be obtained, or if the test cannot be
performed within these limitations it may be neces3.16 CAUSES FOR REJECTION OF TEST
sary to establish revised limits for testing.
READINGS OR RESULTS
The performance test results shall be carefully reviewed within the context of the test agreement per
There are manyconditions that affect the performpara. 3.2 and the proceduresand limitations deance of an ACHE. Some adverse conditions could be
scribed herein. If the test did not.meet these criteria,
a cause for rejection of test readings or results. These
it shall be voided unless otherwise mutually agreed.
may include:
(as weather conditions of high wind, rain, snow, or
extreme temperatures;
3.1 7 POST-TEST UNCERTAINTY ANALYSIS
(h) atmospheric conditions of dust,organics, or
After the test, the uncertainty analysis shall be rechemicals;
(c) site interférence from unspecified
terrain,
peated based on actual variations of test data and
buildings, or other equipment;
degrees of freedom of the individual parameters.
3.15 DEGREE OF CONSTANCY OF TEST
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CONDITIONS
ASME PTC*30 91
0759670 0083249 9
ASME PTC 30-1991
AIR COOLED HEAT EXCHANGERS
SECTION 4
- INSTRUMENTSANDMETHODS
OF
4.3 FAN MEASUREMENTS
4.1 GENERAL
Thefanspeedshallbemeasured
in accordance
19.1
3,
"Measurement
of
with
the
provisions
of
PTC
quired sensitivity or precision
of instruments, and calRotary
Speed."
The
fan
ring
diameter
shall
be
meaibration corrections to readings and measurements.
suredalong two perpendiculardiametersa-cand
Included are instructions as to methods of measureb-d (see Fig. 4.1).
ment, location of measuringsystems,andprecauThe following measurements may be taken for ditions to be taken including critical timing of
agnostic purposes.
measurements to minimize errordue to changing
conditions. The Supplements on Instruments and Ap- O Fan blade minimum tip clearance should be determined by rotating the fan 360 deg. and locating the
paratus(PTC 19 Series) describe methods of meaminimum clearance of the longest blade.
surement, insfruhent types, limits, sources of error,
O Fan blade maximumtip clearance should be detercorrections,andcalibrations.Whenappropriate,and
mined by rotating the fan 360 deg. and locating the
to avoid repetition, this Code refers
to andmakes
maximum clearance of the shortest blade.
mandatory the applicatibn of the Supplements on IniBlade track should be determined by moving
each
strumentsandApparatus(PTC
19 Series). All reblade
past
a
common
vertical
line
on
the
fan
ring
quired
instruments
that
are not covered by
inner wall. Results should be shown
as vertical deSupplements on Instruments and Apparatus havethe
viation from a selected horizontal datum plane.
rules and precautions described completely
in this
Section.
O Fan bladeangleshouldbemeasured(e.g.,
by
For any of the measurements necessary underthis
means of a protractor equipped with a scaleand
Code, instrumentatiqn systems ormethodsother
level). The measurement should be made at the pothan those prescribed herein may be used provided
sition on the blade specified by the fan manufacturer.
they are atleast as accurate as those specified herein.
O Clearances and tracking
of the blade tips should be
Other methods may be employed
if mutually agreed.
measured at the equivalent dynamic position.
Any departure from prescribed methods shall be described in the test report.
This Section describes choice of instruments, re-
0
4.4 MEASUREMENT OF AIR FLOW
4.4.1 This measurement requiresa traverse of air velocities over a selected area: Suitable instrumentsfor
the traverse include the propeller anemometer or a
rotating vane anemometer. Pitot tubes may also be
used for fan ring traverses, as described in PTC 11
1984. Instructions providedwith the instrument must
be followed so as to limitthe overall test uncertainty
to +.5 percent. A minimum timed interval of 30 sec
for individual readings is recommended.Since the
direction of the air flow is not necessarily normal to
4.2 MEASUREMENT OF PHYSICAL DIMENSIONS
The physical data shall be obtained for usa in performance testingand evaluation. Most details for the
tube bundle prqcess side are'defined in the ACHE
data sheet. Othqr data may include:
( a ) face area;
(b) ratio of free flow area to face area;
(c) the total cross-sectional area for fluid flow in
each pass.
-
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MEASUREMENT
ASME PTC*30 91 W 0759670 0083250 5 W
:
HEAT EXCHANGERS
--``-`-`,,`,,`,`,,`---
ASME PTC 30-1991
FIG* 4.1
LOWTlON OF AIRVELOCITY AND TEMPERATUREMEASUREMENT POINTS
ACROSS FANRING
the plane of the area surveyed, it may be necessary
to'correct thereadings for yaw. The anemometer shall
4.4.3 For induced draft units, air flow should bedetermined by traversing the streamsemitting from the
fans. The'recommended minimum number of measurement points and the locationsof these points are
given in Table 4.1. Measurements along additional
diameters maybe necessary to avoid error due
to the
effects of structural members.For additional information on traversing methods, instrumentation, and
evaluation of data, refer to PTC 18 and PTC 19.5.
To illustrate, a 20-point traverse (five measurement
points per quadrant) is made as follows.
The plane bounded by the inner periphery at the
top of the fan ring is divided into ten equal concentric
areas numbered consecutivelyfrom 1 to I O as shown
in Fig. 4.1.
The ring is also divided into four quadrants as
shown.The air velocity is thenmeasured at each
point of intersecfion of the radii a,b,c,
and d with
the inner peripheries of areas, 1, 3, 5, 7, and 9, at
the center. The averagevelocities in comb¡-ned areas
1 2,3 4,5-+ 6, 7 8, and 9 1O are then obtained
be held parallel to the traverse plane, and the actual
direction of air flow during the timed interval estimated. If the angle between the observed direction
of air flow and the anemometer-axisis 5 deg. or more,
the reading shall be correcte!.Specific
corrections
,for yaw shall be determined by calibration prior to
the test.
4.4.2 The selection of the most'suitablearea for the
anemometer traverse shall be guided by the general,
physical
arrangement,
accessibility,
obstructions,
wind conditions, and air temperatùre rise.Because
of the decreased effectof ambient wind, accuracy i.s
usually better when the traverse is made in a high
velocity stream. In the case where these constraints
require that a velocitytraverse be done at the inlet,
a velocity traverse is also required at the exit in order
to allow weighting the exit temperatures.
+ +
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+
+
ASME P T C * 3 O 91 P 0759670 0083253 7
AIR COOLED HEAT EXCHANGERS
O
ASME PTC 30-1991
TABLE 4.1
RECOMMENDED MINIMUM NUMBER OF AIR VELOCITY MEASUREMENT POINTS
FOR FANRINGTRAVERSE
Ring Fan
Diameter, ft
Recommended Number
of Concentric
Areas
for Traverse
Corresponding
Total Number
of Measurements
Corresponding
Measurements
Per Quadrant
12
16
20
20
20
24
28
6
8
10
10
10
12
14
4
6
8
12
16
20
24
O
Measurement
Points Per
Quadrant
Location of Measurement Points,
Distance
From
Point 1
Point 2
Point 4
Point 3
~~
0.2959D
1047D 0,0323D
0.1465D
0.0436D
3
4
5
0.02571)
6 0.1181D
0.0670D
0.0213D
7
0.0568D
0.0182D
a . .
0.081 7 0
0.14651)
0.3419D
0.2261 D
0.1 7731)
Inner Wall of Ring
Fan
Point 5
...
...
0.3557D
0.2500D
Point 6
....
...
...
Point 7
...
...
...
...
0.3664D
0.2685D
0,2012D
0.1464D
0.0991 D
GENERAL NOTE: D is I.D. of fan ring at planeof traverse. Figure 4.1 illustrates the locations for the case
in which five measurement points
per quadrant are used.
O
by averaging the five measurements taken alongthe
inner peripheries of areas 1, 3, 5, 7, and 9, respec-
For forced draft units an exit traverse is normally
required, in conjunction with temperature measurements, so that the weighted exit temperature can be
determined (see para. 4.13).
If the traverse measurements are madein a plane
upstream from the tube bundle face (typical for induced draft units), the plane shall be located at least
five prime tube diameters from the extremit'ies of the
fins to prevent error due to the restriction effect of
the tubes; for downstreamtraverses(typical
for
forced draft units) the requiredminimum distance is
15 prime tube diameters. To minimize error due to
wind effect a suitable shieldis necessary in most instances (Ref. [I]).
--``-`-`,,`,,`,`,,`---
tively. These velocities are plotted against the total
areas bounded by the corresponding circlesas shown
in Fig. 4.2.
The net area below the resulting curve, between
the limits Soand ST, represents the actual volume of
air delivered by the fan per unit oftime.
If mutually agreed upon by the parties to the test,
the foregoing procedurefor determining the airflow
rate may be simplified by averaging directly the 20
air velocities (the readingat the center of the fan is
not used in this method) andmultiplying the resulting
number by the total fan ring area S,.
a
a
4.4.4 In some instances, obstructions in the fan ring,
or inaccessibility, prevent the use
of the fan ring traverse method, and a traverse of the tube bundle is
indicated. The measurement plane chosen shall
be
divided into imaginary rectangularareas (at least 20
or one per 12 sq ft, whichever is greater) with the
sameaspect ratio as the'plane being measured, if
practical. The summationof the productsof the small
areas and the corresponding velocities at their centers will approximate thetotal volumetric flow ofair.
4.5 MEASUREMENT OF AIR-SIDEPRESSURE
DIFFERENTIAL
Normally a Code test will not require the determination of air-side pressure drop. This measurement
is usually takento diagnose a performance problem,
or in the event thatthe parties to the test have agreed
to guarantee the total or static differential pressure
losses.
17
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AIR COOLED HEAT EXCHANGERS
ASME PTC 30-1991
the readings and of such size that theymay be read
to 5 percent of the anticipated value,
1
I
4.
4.5.4 For the readingsa probe shall be connectedto
each leg of the manometer. The instrument shall first
be checked for zero deflection, with the probes locatedatapproximately the sameverticaldistance
apart as will exist during the readings.
4.5.5 Forinduceddraft
ACHE'S, the high pressure
side will be sensed by the probe located at the inlet
side of the tube bundle.This pressure shouldbe fairly
constant and, after proving consistency of reading,
the low pressure probe is positioned and the static
pressure differential recorded.
I
1
A
9
Total Cross-Sectional
Area
4.5.6 For forced draft ACHE'S the low pressure side
will be sensed by the probe located at the heat exchanger outlet. The low pressure area should exhibit
fairly constant pressure; once constancy is verified,
the probe should be left in position for duration of
differentialpressuremeasurements.Thehighpressure side to be probed will be at the fan discharge,
and the. probe should be positioned at the fan discharge area at a location sufficiently downstream of
fan to minimize severe turbulence,
where Va is the average velocity.
FIG. 4.2TYPICALVELOCITY
DISTRIBUTION
ACROSS -FAN STACK
4.6MEASUREMENT OF FANDRIVERPOWER
the pas4.5.1 The static pressure drop resulting from
by
sage of air through the unitshallbemeasured
means of probes designed to minimize velocity effect, anda suitable readout device such
as an inclined
.tube manometer, sufficiently accurate to yield readings within r t 5 percent of the true values.
4.5.2 A wall tap, comprised of a smooth 1/8 in. di-
ameter drilled hole ,without burrs or obtrusions is
suitable in uniform low velocity flows; however, the
ùse of a;cylindrical Fechheimer probe or a two- or
three-dimensionalwedgeprobeisrecommended
(see PTC 11-1984, Fans for further information). The
probe shall be calibrated before each- use.
If an accurate static pressure measurementis necessary, a traverse using the procedures described in
para. 4.4 is required.
'
4.5.3 The manometer shall be an inclined tube gage
calibrated for direct readings in inches of water. The
scale range shall be selected
to suit the magnitude of
Test power isthe shaft outputof the prime mover,
For electric motors, test measurements are made at
the input, andthe output power is computedby multiplying input powerby motor efficiency. Acceptable
instruments for determining power, in preferred order, are:
(a) wattmeter
(b) voltage, current, power factor meters
When readings are taken at a load center located
a substantial distance from the motors, corrections
should be made by direct measurement of voltage
drop (orby computation of loss) between loadcenter
and motor. To enable this correction
to be made, the
length and gage of cable involved should be-measured. A measuredorcomputedvoltagedropbetween the load center and one motormay be applied
to the other motors by ratioing their distances from
the load center.
For prime movers other than electric motors, the
methodfordeterminingpowershallbemutually
agreed upon prior to the test.
18
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ASME PTC 30-1991
tion should be chosen for the measurement that is
unobstructedupwindand at anelevationapproximately midway between the average air inlet plane
elevation and the average air exit plane elevation. If
such a location is impracticable,an alternate location
.may be agreed upon by the parties to the test.
4.7 MEASUREMENT OF SOUND LEVEL
This subjectistreated
in PTC 36-1985.
o
4.8 MEASUREMENT OF ATMOSPHERIC PRESSURE
Atmospheric pressure shall be measuredby means
of a mercury barometer.
If mutually agreed by the parties to the test, the
barometric pressure may be obtained from a nearby
weather bureau station. If this method is used, it is
necessary to establish whetherthe readings given are
for station or sea levelpressure.Thereadings obtained shall be corrected for the difference in elevation of the barometerand the unitbeing tested.
Results shalt be based on atmospheric pres.sure at
station level. Readings may be corrected to sea level
if desired. Detailsof the procedure for correction are
given in PTC 19.2.
4.9 MEASUREMENT OF ENVIRONMENTAL
4.1 1 MEASUREMENT OF AIRTEMPERATURES
4.1 1.1 PTC 19.3 shall be used to stipulate satisfactory instrumentation and details of construction
of
sensor wells,the reading of the instruments, and their
calibration and corrections.
Theuncertainty
of temperaturemeasurements
shall not exceed the larger of the following values:
(a) 0.2"F, or
(b) two percent of the smallest of the following
three key temperature differences:
(7) the temperature range of the process fluid
(unless isothermal)
(2) the temperature range of the air
(3) the minimum approach temperature difference. .
Satisfactoryinstrumentsincludesuitable
ASTM
mercury-in-glass thermometers, thermocouples, calibrated sensors with signal conditioner such
as resistancetemperaturedevicesorthermistors,or
equivalent.
The sensing elements shall be exposed to the atmosphere, but shielded from direct sunlight or other
radiation source by means of an opaque shield.
.
EFFECTS
Prior to the test, a survey of the area surrounding
the unit shall be conducted jointlyby the parties to
the test. AI1 conditions that may contribute to variations in performance, such as heat sources affecting
inlet air temperature, and nearby buildings or structureswhichmay cause aircurrentsthatresult
in
warm air recirculation, or .in reduced fan performance, shall be investigated. Measurements necessary
to map these effects during the test shall be determined by mutual agreement, .and substantiatingtest
data shall. be obtained as necessary. Ambient temperature measurements shall be takenin accordance
withparas. 4.11 and 4.12 of thisCode.Measurements should be made in all locations, simultaneously if possible,or in. rapidsuccession. If such
locations are not accessible orthe area surrounding
the ACHE contains elements (see above) which can
affect the ambient temperature, a suitable location
for thesemeasurementsshallbemutuallyagreed
upon.
4.1 1.2 The wet-bulb temperature measuring instruments should be mechanically aspirated and incorporate the following features:
(a) A calibrated temperature sensor whose uncertainty is less thanf 0.1"F in the range of the expected
test temperatures.
(b) Sensing elements shielded from direct sunlight
or other radiation source. The inner side
of the shield
shall be essentially at the dry-bulb temperature.
(c) Wicking coveringthe sensor shall be clean and
continuously supplied froma reservoir of distilled or
demineralized water. The wick shall abesnug fit and
extend at least 1 in. over the active portion of the
sensor.
(d) The temperature of the water used to wet the
wick shall be at approximatelythe wet-bulb temperature.
(e) The air velocity over the wick shall be continuous at approximately 1000 Wmin.
4.1 O MEASUREMENT OF WIND VELOCITY
The instrument recommended is
eitherthe rotating
cup or rotating vane anemometer with preferably a
continuous readout or recording capability. A loca19
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AIR COOLED HEAT EXCHANGERS
ASME PTC 30-1991
4.1 2 MEASUREMENT OF AMBIENT AND
ENTERING AIR TEMPERATURES
. A
This survey shall consistof two ambient wet- and
dry-bulb temperature measurements and a suitable
number of entering dry-bulb temperature measurements.
The ambient wet-. and dry-bulb temperature measurements shall be takenat approximately 5 ft above
the ground elevation not less than 50 or more th.an
100 ft upwind of theequipment. Theseshall be
spread along aline which brackets that flow. If these
locations are inaccessibleor contain,elementswhich
can affect the reading of wet-bulb temperature, alternate locations shall be mutuallyagreed upon.
Entering dry-bulb temperature measuring stations
shall be selected on an- equal-area basis, and shall be
located in a plane6 in. below thefan ring for forced
draft, and 12 in. below the finned tubes for induced
draft units. The sensing elements of the thermometers, or thermocouples, shall be properly.locatedand
shielded to prevent appreciable error due to radiation. The recommended number of stations is given
in para. 4.4. If the maximum and minimum temperatures differ by 5°F or more due to warm air recirculation, or environmental effects, additional stations
shall be selected, the number and location of. these
stations shall be determinedby mutual agreement of
the parties to the test.
4.1 3 MEASUREMENT OF EXIT AIR TEMPERATURE
Unless otherwise agreedby the partiesto the test,
coincident temperatures and velocities shall be measured atall selected stationsso that the weighted exit
air temperature can be calculated. The instruments
to be used shall be as specified in para. 4.11.
rectangular areas (at least 20 or one per 12 square
feet, whichever is greater) with the same aspect ratio
as the plane being
measured, if practical. Shields shall
be provided for the temperature sensing elements
to
prevent error due to dilution by outside air, or due
to radiation from the sun or other sources. The temperature measurement devices shall be located
a sufficient distance from the ACHE to minimize the effect
of the tube wakes (usually 15 prime tube diameters
is sufficient).
4.14 MEASUREMENT OF PROCESS FLUID
TEMPERATURES
4.64.1 The uncertainty of temperaturemeasurements shallnot exceed the larger of the two following
values:
(a) O.Z"F, or
(b) two percent of.the smallest of three key temperature differences;
(7) the temperature range of the process fluid
(unless isothermal)
(2).the temperature rangeaf the air, or
(3) the minimum approach temperature difference. See para. 4.1 1 for satisfactory instruments.
4.1 4.2 The measuring stations shallbe located close
enough to the unit to prevent appreciable error due
to temperature change occurring between the stations and the unit. Where stratification
is a possibility,
preliminary tests shall beconducted to determine the
magnitude of possible resultant error.
These shall be
made a partof the test report.
4.15 MkUREMENT OF PROCESS FLUID
PRESSURES
4.13.1 Induced Draft Units. Measurement stations
shall be locatedprior to the testperiod in accordance
with para. 4.4.3 so th'at the measurements will best
represent the true bulk temperature. For multiple-fan
units, fewer stations may be used if agreed upon by
the parties to the test. The temperature profile of one
fan shall be investigated thoroughlyprior to the test
period to ensure sufficient accuracy; the data shall
be made a partof the test report.
The requireduncertainty limit of fluid pressure
measurement devices shallbe two percent of the absolute fluid pressure. Instrument selectionand details
in accordof measurement techniques shall be made
ance with PTC 19.2. Satisfactory instruments include
pressure. gages,. manometers, pressure transducers,
or other equivalentdevices.
Measuring stationsshall be locatedas close to the
unit as practicable. Corrections shall be made
for line
losses, fitting losses, etc., that result in pressure difference between.the-measuring stations
and the unit.
4,13,2 Forced Draft Units. .Measuring stations shall
belocateddownstream of the tube bundles.The
measurement plane shall be divided into imaginary
20
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AIR COOLED HEAT EXCHANGERS
4.16 MEASUREMENTOFPROCESSFLUIDFLOW
RATE
4.16.1 The recommended uncertainty limit of fluid
flow measurement devices shall be two percent of
the total process flow through the test unit. Instrumentselectionanddetails
of measurementtechniques
shall
.be
in accordance with PTC 19.5.
Satisfactory instruments include venturi meters, orifice meters, flow nozzles, pitot tubes, turbine meters,
or other equivalent devices.
Alternatively, flow ratesmaybedeterminedby
plant heat balance method,provided the uncertainty
does not exceed two percent.
4.16.2 Measurements shall be.made in the piping
leading to and as close as possible to the unit. If this
is not practicable, an alternate location shall be selected by mutual agreement, and corrections made
as necessary to determine the actual flow into the
unit.
4.1 7 .MEASUREMENT OF COMPOSITION OF
PROCESSFLUID
--``-`-`,,`,,`,`,,`---
Sufficient samples of the process fluid shall beobtained to enable determination of the composition of
inlet and outlet streams.The methods of analyses
shall be mutually agreed upon by the parties to the
test.
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ASME PTC 30-1991
AIR COOLED HEAT EXCHANGERS
- COMPUTATION OF RESULTS
SECTION 5
5.1
GENERAL
portunity for immediate discoveryof possible errors
in instruments,procedures,andmethods
of measurement. Guidance for the review of data and test
conditions is given in paras. 3.12 through 3.16; significant deviations shall be corrected prior tothe official data collection if practicable. Any uncorrected
or uncontrollable conditions that violate the provisions of paras. 3.12 through 3.16 shall be described
i n the test report. At the end of the test period, but
prior to removal-of test instrumentation, a final review of the data shall be madeto determine whether
or not an immediate repeat
test isnecessary.This
review will also assistin the establishment of the reliability of the test; it shall include a post-test uncertainty analysis for evaluationof deviations from ideal
of the following, and the effects of these deviations
on the test results:
(a) comparison of test and design conditions;
(b) test siteenvironment,includingatmospheric
conditions;
(c) fouling;
(d) leakage, process-side and air-side;
.(e) process fluid distribution;
(0 air distribution;
(s, steady-state conditions;
(h) measurement uncertainty;
(i) location of measurement stations;
0) qualifications of test personnel, and validity of
test data;
(k) process fluid composition.
This Section covers the reduction of the test data,
computation of test results, adjustment of results to
design conditions, and interpretation of adjusted results by comparing them to design. This Section assumes that the ACHE surface is of a typical circular
geometry. If not, the parties to the test must adjust
the computations as appropriate. Thebasicprocedure for computation of performance capability is:
.(a) review the raw test dataand select the readings
to be used onthe basis of the requirements of paras.
3.12 through 3.17;
(b) average the selecteddata;
(c) compute mass and heat balances, and establish
whether or not the.provisions
of paras. 3.14 through
3.16 have been met;
(d) compute test value of effective mean temperature difference;
(e) compute overall heat transfer coefficientat test
conditions;
(f) establishindividualresistancesat
test conditions;
(g, adjust air flow rate and air film resistance to
design fan power and design air density;
(h) adjust test process-side pressure dropto design
conditions, and compare to specification value;
(i) compute the capability of the unit at design
process temperatures, design inlet air temperature,
anddesignfanpower.Themethodpresentedisan
iterative one, since corresponding heat load, process
flow rate, inside film resistance, and effective mean
temperature difference areall unknown.
'
0
5.3 REDUCTION OF TESTDATA
The purpose of averaging the raw test data is to
give a single set of numbers which is representative
of the collected data to be used in calculations to
determine performance. Multiple readings taken over
time and/or readingsof the same parameter by multiple instruments at given
a
station shall be arithmetically averaged.
5.2 R M E W OF TEST DATA AND TEST
CONDITIONS
@
Theraw test data shall be carefully reviewed
to
ensure selection of entries that will accurately representtrueperformance.Thisreviewshouldbe
started at the beginning of the test, providing an op23
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AIR COOLED HEAT EXCHANGERS
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The density of dry air can be calculated from
5.3.1 Air-Side Data Reduction
.
(a) Air Velocity. Individualairvelocity measurements shall be corrected for instrument calibration
and then averaged as discussed in para. 4.4
(6) Air Temperature. Air temperature data readings
shall be averaged for each set of test data. Exit air
temperaturesshallbeaveraged
bythe. mass flow
weighted average method shown in Eq. (5.1); however, variations in inlet air temperature are normally
small enough to allow arithmetical averaging of the
temperatures alone.
paB/t,
= 1.325
(5.3)
(b) Computation of Heat Load:
Q, =
(W)
(Hiz - H,,) (Note 3,
(5.4)
5.4.2 Computation of Process-Side Mass Flow Rate
and Heat load
(a) Computation of Mass Flow Rate
N
2
t =
tnPnvnsn
II-1
(5.1)
N
2
Pnvnsn
(b) Computation of Heat road
n-l
where n is an individual measurement
(c) Static fressureor Differentialfressure. The readings shall be arithmetically averaged.
Q, = (W CH,,, - H,,)
(5.6)
The enthalpy of the process fluid at the entrance
and at the exit shall be determined by means,and
from data sources, mutually agreed upon by the par(a) Process Temperatures. Readingsof process fluid
ties
concerned prior to the test. For process fluids
.temperatures ata given station shall be arithmetically
with
no phase change, the above heat load equation
averaged.
can
be
written
(b) Process Flow:Process flow measurements shall
be calculated in accordance with ASME PTC 19.5,
Fluid Flow MeasurementProcedures, or its interim
supplement, ASME Fluid Meters, Part II.
(c) Processfressure.Processpressuremeasure5.4.3 Computation of Heat Balance Error. The perments shall be calculated in accordance with ASME
cent error in heat balance is calculated by
PTC 19.2.
5.3.2 Process Fluid Data Reduction
1 4 - Qal
5.4, DETERMINATION OF MATERIAL AND HEAT
BALANCES
Percent
Error
Both the air-side and process-side heat loads are
to be calculated. The objectivesof these calculations
are two-fold: (I) to determine the heat load of the
heat exchanger under the test condition, and ( 2 ) to
check the validity.of the set of test data obtained. To
calculate the heat loadsfor both the air and prqFess
sides, the air and process fluid mass flow rates are
first calculated.These flow ratesarethenused
to
calculate the heat loads.
(a, - Q1,.
=
Q, + Q,
x 200
,
is the absolute value
If the percent error is within the acceptable limit
of 15 percent as stated in para. 3.16, the heat load
Q to be used for data interpretation can be one ofthe following:
(a) the air side heat load Q,
(6) the process side heat load Q,,
(c) the average heat load (Q,
QJ2.
+
5.4.1 Air-Side Mass Flow Rate and Heat load
(a) Computation of Mass Flow Rate of Dry Air. For
computation of air mass flow rate,
W
= (pJ(VJ(SJ(60)
zThe constant1.325 applies for U.S. Customary Units of B and tw
¡,e., in. Hg and R.
'Values of H,, and Ha2are determined from enthalpy data, using
the corresponding test valuesoft, and t2.
(5.2)
'The factor 60 applies to US. Customary unitsof p. ,V, ,Sa.
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I
ASME PTC 30-1991
The selection of Q shall be based upon the value
thatprovidesthelowestestimatedoveralluncertainty.
If the percent erroris not within acceptable limits,
no further calculations are advisablethe
and
test shall
be repeated, unless otherwise agreed.
EMTD =
EMTD is the effective mean temperature difference
between the hot stream and the air stream.
.
(.§.13)(Nof=
4,
where n denotes the individual zone
For cases where the overall heat transfer rate varies
through the unit, such as changes from turbulent to
laminar flow or units with condensing and subcooling, then it is necessary to divide the unit intozones
and treat each zoneas a separate case. This involves
obtaining aseparate heat load, EMTD andU for each
zone. This type of operation may require special temperature measurementswithin each zone rather than
only recording the inlet and outlet terminal temperatures of each stream. These intermediate temperaturesmay beimpractical to obtain. In suchcases
prior agreement should be reached between the parties involved concerning the actualdata reduction
procedures.
In the typical air cooled
heat exchanger design,the
flow arrangement is not normally pure countercurrent or cocurrent. Most designs are fabricatedfor air
flow at right angles to the tubes and crossing over
one or more tube rowsin series. The process fluid in
the tubes, at any one point, travels atright angles to
the air flow, and the correction factor
F is usually less
than one.
The correction factor F for the most common arrangements may be obtained from Figs. 5.1 through
5.8. Correction factors are only applicable for the
flow arrangements shown in the figures. All of these
figures are predicated on using the countercurrent
flow formula for calculating the LMTD.
For other types of flow, not covered by these figures, the calculation of F shall be a matter of agreement of the parties involved in the test. If the process
fluid temperature is constant, the EMTD is calculated
by Eq. (5.12).
5.5 COMPUTATION OF EFFECTIVEMEAN
TEMPERATUREDIFFERENCE
EMTD = F x LMTD
QA
(5.9)
where
F = correction factor for deviation from true
countercurrent or cosurrent flow
DifferLMTD = LogarithmicMeanTemperature
ence
For strictly countercurrent flow or cocurrent flow
and for cases where the temperature of the process
stream is constant, the LMTD is calculated from
Countercurrent Flow:
Cocurrent flow:
5.6 COMPUTATION OF OVERALLHEAT
TRANSFER COEFFICIENT
Constant Process Fluid Temperature: T, = T, = T
wis calculated from
v =(A,)
Q"
(EMTD")
(5.14)
where Q" is the test heat load, expressed in Btu/hr,
selected as best representing the thermal duty
of the
Where U is essentially constant over a temperature heatexchanger.Thevalueused
must always be
'range, .but release of heat versus temperature is a
4This procedure is fundamentally correct only for pure countercurved line, the heat release curve may be divided
withcurrent or cocurrent flow, but yields an approximate answer
into zones using a straightline release in each zone.
out requiring detailed stepwise calculations. It may be used with
With this situation, the EMTD for the whole unit is
mutual agreement of the parties to the test; otherwise, another
calculated from the following equation:
agreed procedure may be used.
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AIR COOLED HEAT EXCHANGERS
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A S I E PTC*30 72
AIR COOLED HEAT EXCHANGERS
ASME PTC 30-1991
is equal to the air pressure rise providedby the fan.
Therefore, to measure the cooling system air pressure
loss, one caneither measure these component losses
separately or in combination, or one can deducethe
total losses from the fan drive system power consumptionandthemeasured
airflow, Thefan drive
system power consumption is comprised of the air
energy losses and the drive system mechanical and
electrical energy losses. Generally, in a performance
test, it may not be necessary or desirable to measure
each of these air pressure losses separately, andusually it is. preferable and ‘easier to measure only the
cooling system power consumption for comparison
with design specifications and/or performance characteristic data provided by the system supplier.
clearlyidentified, e.g., air-side, process-side, arithmetic average, etc.
Thereferenceareamay
be any.convenienf mutually agreed upon heat transfer surface. There are
four commonly used reference areas.
where
Lfn = the length of finned portion of tube
LIfno = the outside diameter Óf fin
DR, = the outside diameter of root
Dpo= the outside diameter of prime tube
L = the total length of tube
(Note: Other symbols as defined in para. 2.2)
PRESSURE LOSSES
The pressure loss betweenmeasuringstations is
simplythedifferencebetweenthemeasurements
taken at these locations. Thetest measuring stations
should be located in such a way that they will provide
a pressure measurement at the required design stations. If not, consideration must be given to the .effects of the following factors:
(a) gravity.
(b) fluid velocity
(c) flow obstructions
(d) fluid properties and flow rates
Figure 5.9 is a schematicrepresentation of the
process fluid piping for an ACHE. The measuring stations (MS) and design stations (DS) have been deliberately depictedin different vertical locations
in order
that the following discussion and calculation procedures can encompass this possibility.
Equation (5.19) shall be used to adjustthe test
value of pressure loss across the measuring stations,
to a deduced value of total pressure loss across the
design stations at the test conditions.
Outside
(This is a fictitious area)
ARo
= T
(5.16)
DRo
5.6.3 Prime Surface Basedon Inside Tube Diameter
Up,.)
A,,, = rND,L
5.6.4 Prime Surface
Based
Diameter (Apo)
(5.1 7 )
on Outside Tube
Apo = rNDpoL
(5.18)
Thereferenceareaupon
which theoverallheat
transfer coefficient is based must be clearly identified
in connection with any statement of that coefficient.
The overall heat transfer coefficient is meaningful
only if all of the assumptions required for the mean
temperature difference formulationare satisfied.
(5.19)
where:
APmStertis theprocess fluid pressure differential as measured by experimental data at the selected measuring stations.
APgM-D is the change in the measured process fluid pressure differentialcaused by differences in elevations between the measuringstations and design
stations and/or differences in process fluid densities in the inlet piping and the outlet piping.
5.7 DETERMINATION OF AIR-SIDE PRESSURE
LOSSES
The summation of the air pressure losses of the
tube bundle,flow obstructions, and airturning losses
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5.6.2 Outside SurfaceBasedonFinRoot
Diameter (ARo)
5.8 DETERMINATIONOFPROCESS FLUID
' A S M E P T C * 3 O 71 E 0759670 0083260 8 W
ASME PTC 30-1991
AIR COOLED HEAT EXCHANGERS
These losses canbe evaluated at the test conditions
APgD-D is the change in the measured process fluid presusing thefollowing equations and recommendations:
sure differential between design stations caused
by differences in elevation Òf the design stations
5.8.3.1 PipeandBundleTubeFriction
(MoB-,).
and/or differences in processingfluid densities in
These losses can be calculated using Eq. (5.23).
the inlet piping, the outlet piping, and in the bundles. It may not be necessaryto include this term
(5.23)
depending on howthe pressure dropis quoted.
AP,
is thechange in themeasuredprocess fluid pressure differentialif static pressures are measured.
Properties should be evaluated at the mean temperature. For evaluationof friction factor, fM, refer to
Fig. D.1, Appendix D.
APDS,=, is the deduced process fluid total pressure loss at
the test conditions.
5.8.3.2 Obstruction losses Due to Contractions,
Expansions,
Bends,
Fittings
and
These
losses can be calculated usingEq. (5.24).
APoBDs is thesum of all the flow resistances due to ob-
structions between design stations,
APO,,,
is the sum of all the flow resistances due to obstructions between measuring stations.
(5.24)
Detailed proceduresfor solving the elements
of Eq.
5.1 9 are presentedin the following paragraphs.
Theevaluation of K will depend on the type of
obstruction as described below.
Abruptcontractionandexpansionlossesyielda
value of K as follows:
5.8.1 Gravity C A P g ) . Differences in elevations and/or
densities will have aneffecton process fluid pressure
measurements.Theseeffectscanbeevaluated
by
means of Eqs. (5.20) and (5.21) with reference to Fig.
5.9.
K= 0.5 x (1 - pz) incontraction
K = (1 - ßz)* in expansion
(5.25)
(5.26)
where ß is the ratioof the smallerto the larger inside
pipe diameter.
(5.21)
5.8.3.3
Pipe and Cooler
Tube
Bend
losses
These losses yield a K coefficient which is
not explicitly defined by any correlation. Reference
E21, however, presents some data for 90 deg. bends
along with a correlation for more than one bend in
series which is not simply the sum of the number of
90 deg. bends.
5.8.2 Fluid Velocity (@J, If total pressures are measured! AP, is included in the total pressure. If static
pressures are measured, APw can be evaluated using
Eq. (5.22).
5.8.3.4
losses Caused by Various
Fittings
The valuesof the loss coefficient, K, for pipe
fittings,valves,etc.,are
dependent on the specific
geometryinvolvedandcannotbegeneralized.For
this reason it is best to plan the instrumentation so
that there areas few such lossesas possible between
measuringstations.Forthosecomponents
which
must be evaluated, there are data available
from manufacturers, such asRef. 131, and reference will have
to be made to these for the particular type of fitting
of interest.
(5.22)
(APoBJ.
where:
AP, = velocity pressure differential, Ibf/ft2
5.8.3 Flow Obstruction @APoB). Obstruction losses
between measuring stations may include effects due
to:
(a) pipe and bundle tube friction
(b) contractionsand/orexpansions in the pipes
and bundle tubes
(c) pipe and bundle tubebends
(d) the presence of fittings such as bends, valves,
flow meters, tees, couplings, etc.
Summarizing,
27
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ASME P T C * 3 0 91,
0757670 0083261 T
m
AIR COOLED HEAT-EXCHANGERS
ASME PTC 30-1991
Fan HorseDower+ = FanHorseDower"
5,9 ADJUSTMENTS OF TEST DATA TO DESIGN
CONDITIONS
Since tests are rarely run at design conditions, the
recommended procedure is to adjust the ACHE performance results determined under
test conditions to
design conditions and compare these adjusted values
with the design values.
When a procedure for'acceptance testingis to be
adopted, a discussion between the interested parties
is essential to establish agreement as to the method
by which data will be adjusted from test to design
conditions, Presented below are methodswhich may
be usedto make adjustments required in some of the
more commonly encountered situations. Before using these methods, the parties involved in the testing
should assure their applicability to the test under consideration. Adjustments for some of the more complexcasescanbemade
using the relationships in
Appendix D.
--``-`-`,,`,,`,`,,`---
5.9.1 Adjustment of Air-Side Bundle Pressure Drop
and Fan Performance. When the test is run at conditions other than design air densities, velocities, or
fanspeed, testmeasurementsmaybeadjusted
to
their equivalent values at design conditions
by use of
the following equations. The user should recognize
that accuracymaysuffer
if adjustmentsaremade
from conditions which vary significantly from design
conditions (see limitations in paras. 3.14 and 3.15).
NOTE: The cautions presented above applicable to the pressure
drop evaluation are also applicableto the power adjustments.
Adjusted driverinput horsepower may be obtained '
by introducing the driver and drive train efficiencies.,
Driver Input Horsepower+ =
Fan Horsepower+
(5.31)
qdrlvw qdrlve iraln
(c) Air Density Determinations
For determining thedensities required in the pressure drop and horsepower adjustments,Eq. (5.3) may
be used.
NOTE: This equation is used for the more typical applicationsand
neglects humidity effects. If widely variant humidity conditions
exist with respect to design, a more precise evaluation using psychrometric data may be appropriate.
(d) Air Flow Determination
To adjust the test airflow to the conditionsof design fan horsepower and design air density, use
(5.32)
(a) Air-Side Bundle Pressure Drop
5.9.2 Adjustments of Single PhaseProcessiSide
Fluid Pressure Drops
NOTE:
For
multi-phase cases, the user should
refer
Appendix D
or
Tocompare the measuredprocess-sidepressure
drop to the design value, adjustments may be necessary to compensate for the following:
.Process fluids with properties or conditions other
than design
.Process flow rates other than design
Because of the simplifying assumptions made in
the derivation,significantchanges in the Reynolds
number, V, or RPM, between design and test conditions will adversely affect accuracy. The 1.7 power
hasbeenestablished
as reasonableapproximation
empirically, but may vary givendifferent system configurations,
Such adjustments may be made using
(b) FanPower Adjustments
FanHorsepower+ = FanHorsepower"
x
+ pz)*
(Pl
+ Pz)"
APp' =
x
(5.29)
?)'''($($Y2,
e(
for turbulent flow
(5.34)
28
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0759670 0083262 L
ASME PTC 30-1991
AIR COOLED HEAT EXCHANGERS
from test conditions to design conditions, andfinally
recombine the component coefficients to calculate
an adjusted overall heat transfer coefficient.
prior to testing reAgreementmustbereached
garding use of the adjustment procedure presented
below or an alternate.
Densities and viscosities shouÌd be evaluated
the at
mean temperature.
NOTES:
(1) This adjustment presumesthat inlet and outlet pressures were
measured attheir design locationswithin the system. If this is
not the case, adjustments must be made in accordance with
para. 5.8.
(2) Throughout Section 5, Re, of 2,300 is taken as a distinct separation between laminar andturbulent flow. Of course, a distinct separation doesnot exist. If Re, is found to be in the range
of 2,000 to 10,000, the user may refer to Appendix D for a
more rigorous treatment.
(3) If the Reynolds numbersfor both the
design andtest conditions
do not fall in the same regime, the simple ratios above donot
apply; in that situation, the user must refer to Appendix D.
(4) For those casesin which the fluid in thetest is in a single phase
throughout the system, temperature andvelocity variations behveen design and test conditions will be the only parameters
affecting the pressure drop measuremenfs. If the fluid is a liquid, the variations in temperature will usually cause only slight
variations in density and, in general; density may be neglected
in the above equations. The viscosity may or may not change
significantly, depending on the fluid and temperature ranges
involved, If the viscosi@or frictionfactor varies by a factor of
two or more from inlet to outlet, pressure drop must be evaluated on an incremental basis. The formulas presented above
presume pressure drop variations through the tubes are representative of pressure drop variations through all components
between pressure measuring stations.If this is not believed to
of variations in pressure
be the case, a more detailed evaluation
drop through individualcomponents of the heat exchangermay
be desirable.
-
@
STEP I
Determine the overall reference surface heat transfer coefficient as indicatedby the test result.
'
Up = Q"/(A,X EMTD")
See para. 5.4 for development of Q" and para. 5.5
for development ofEMTD".
STEP 2
The test overallreferencesurfaceheattransfer
coefficient must be broken down into its component
parts. The following equation represents the normal
heat transfer resistances which may be encountered.
5.9,3 Adjustment of Overall Heat Transfer Coefficient. To adjust measured overall heat transfer coefficients tothe design conditions, adjustments may be
necessary to compensate for the following:
(a) processfluidswithpropertiesorconditions
other than design
(b) process flow rates other than design
(c) air flow rates other than design
(d) air at conditions other than design
Adjustments for commonly encountered applica-in flow regime
tions without phase change or change
may be made using the procedure outlined below.
Adjustmentsfor otherless-frequentlyencountered
situations can be made using
the relationships in Appendix D. Particular care should be taken to assure
results obtained with the equipment and test under
considerationareappropriateforanalysis
by the
equations proposed. The user must recognize that
accuracywillsuffer if adjustments are made from
conditions which vary significantly from design. See
paras. 3.14 and 3.15 for limitations.
In general, the approach presented is to calculate
the overall heat transfer coefficient from the test results, break this coefficient into its component parts,
adjust those component coefficients which change
Inside
(process
Inside
Fouling
fluid) Film
Bond
Wall
Prime
A,(
2rLNkR
))
+
(2)(
1
Fin
and
Air
Film
Fin Root Wall
.(a)
Outside Fouling
29
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ASME P T C * 3 0 91
Not for Resale
(5.35)
m 0757670 0083263
ASME P T C M 3 0 91
3
AIR COOLED HEAT EXCHANGERS
ASME PTC 30-1991
The values of allthe individual components which
comprise the right side of this equation must be determined. Some may be calculated directly by available correlations, some must be assumed and agreed
uponby the.parties to the test as discussed below,
and the final factor (either
the air-side or process-side
film coefficient) will be determinedin Step 3 by solving the above equation.
The decision as to whetherthe air- or process-side
film coefficient is calculated directly should be made
on the basis of which can be determined more accurately. In cases where it is uncertain which coefficient may be determined with greater confidence, it
may be agreed to calculate both and use the coefficient showing the lower thermal resistance to solve
for the other'in Step 3.
A discussion of how each component may be determined follows.
Inside (Process Fluid) Film:
If the process fluid is a liquid in turbulent flow in
a plain tube (no internal enhancement), the valueof
h; may be evaluated using the Sieder-Tate equation
(Ref. [41):
(p)0'33
(
.
determine fouling resistance during equipment testing. Fouling resistances shall be agreed on as stated
in para. 3.2,
Refer to Appendix E for additional discussion of
fouling.
Prime Wall:
This resistance-is calculated directly usingthe applicable part ofEq. (5.35).
Bond:
The value of the bond resistancé, //hb, will depend
upon the type of extended surface being used, the
tube and fin materials, the temperature levelof application,and the manufacturing practice. In many
cases, the value of this component willbelow in
comparison with other terms, making it insignificant.
If this is thought not to be the case, it is suggested
that the manufacturer's design value for this term be
used in the calculation. However, mutual agreement
on this matter must be reachedby the parties to the
test.
Fin Root Wall:
The value of this componentwill be small in comparison with other terms, making it insignificant in
most cases. This resistance is calculated
by the basic
relationship shown in Eq. (5.35). Depending on the
details of fin construction, assessmentof the outside
radius of the fin root wall (r,,) ,may require considerable judgment.
(5.36)
In cases of gaseous process fluids:
Fin and Air Film:
This term must be evaluated by first determining
the air-side film coefficient. An exact evaluation of
this coefficient is difficult
to develop dueto the complex shape of the heat transfer .surface involved. It
may be agreed by the parties to use the manufacturer's proprietarydata.todevelop thisxoefficient.If not,
it is suggested that the following equation (Ref, [5])
for finned banks of tubes be used as a reasonable
approximation:
The physical propertiesin the above equations are
evaluated at .the average fluid temperature .except
p,;w which is evaluated at the surface temperature.If
the process fluid iswater,Figs.D.2aandD.2bof
Appendix D may be used to evaluate h;.
NOTE: The above formulas are applicable for non-condensing situations with the process fluid in turbulent flow (Re, > 10,000).
For cases in which Re, is below 10,000, refer to Appendix D.
Inside Fouling:
Of the component resistances, fouling is the most
difficult to determine. There is no practical way to
(5.38)
30
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r
ASME P T C * 3 O ell M ' d 7 5 7 b 7 0 0083264 5
=
ASME PTC 30-1991
AIR COOLED HEAT EXCHANGERS
TABLE 5.1
VALUES OF Fe FOR EQ. (5.38)
No. ofTube
Tube
RowArrangement
Deep
. .
1
2
3
4
5
(3) F& is tube row arrangement factor; values are given in
Table 5.1,
6
8
10
Once thefilm coefficient is eualuated, it may then
Row
Factor, F,
0.78
0.88
0.93
0.97
0.98
1.o0
1.o2
1.O25
GENERAL NOTES:
(a)These factorsareapplicable for the normalstaggeredtube
arrangement.
(b) Values in this table are calculated from Fig. 11 of Ref. 161,
using V,, = 1000 feet per minute and using the value for 6
rows as a base, since Eq. (5.38) is based on 6 rows.
be used in the determinationof the fin efficiency +Of,,.
Figures 5.10 thfough 5.13 may be used in this evaluation, Symbols in these figures are defined below:
h = heat transfer cuefficient
I = mödified Bessel function of the first kind
K = modified Bessel function of the second
kind
k
= thermal conductivity of fin material
n = a constant, order of Bessel function
U = function of x defined by
STEP 3
Solve for the component resistance not determined
by the correlations
by subtracting the
sum of the evaluated component resistances from the overall heat
transfer resistance.
where i = G;
c = a-constant; p = a constant; a =
cross-sectional area of fin normal to x axis, and A = fin
surface between origin and pointx.
STEP 4
The components on theright-hand side of Eq.
(5.35) must be adjusted to design conditions. The
only Components which will be affectedby these adjustments are the inside film resistance and equivalent conveciion and conduction resistance of the fins.
The adjustments may be madeas follows:
= fin height
x = distance along axis normal to basicsur-
W
face
= half thickness of fin at point x
4 ß = constants
b, e = conditions at base and edge, respectively
y
Inside.(Process Fluid) Film:
The Sieder-Tate relationship may be used to ratio
turbulent test and adjusted design coefficients
For additional discussion of finefficiencies andnumerical relationships for calculation of the efficiencies, the parties may refer to Ref.171.
With the values of
and h: established, the
equivalent convective and conductive resistance of
the fin may be calculated using
the relationship given
in Eq. (5.35). The user must be cautioned that the
method presented aboveis approximate and does
not
address all types of fin configuratiöns and tube arrangements.
The physical propertiesin the above equation are
evaluated at the average fluid temperatureexcept
ppd which is evaluated at the surface temperature.
Outside Fouling:
Thisresistance, like h i d e Fouling, is difficult to
determine. The provisions of para. 3.7(bj shallbefollowed, and a value agreed on prior to the test,as
stated in para. 3.2.
NOTE: The above equation is applicable for non-condensing situations with the process fluid in turbulent flow (Re > 10,000).
31
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NOTES:
(1) Go.,
is the mass flow rate evaluatedwith respect to the free
flow area. .
(2) Equation (5.38) is applicable for Re from 1000 to 20,000, where
ASME P T C * 3 O 9 1 - = 0759670 0083265 7
AIR COOLED HEAT EXCHANGERS
ASME PTC 30-1991
heat load, process flow rate, inside
film resistance,
and EMTD are all unknown.
The recommended procedure for determinationof
capability is:
(7) Assume a value of process fluid flow rate, W+.
(2) Computecorresponding heat. load from Eq.
(5.6)or (5.7),as appropriate.
(3) Adjust the test air flow rateto design fan power
and air density:
Fin and Air Film:
Equation (5.40)may be used to yield an approximateratio of test and adjusted design film coefficients
NOTE:Theabove
20,000,where
equation is applicable for Re from 1000 to
(4) Compute t: at design fan’ power from
If the film coefficient is not greatly changedin the
above adjustment, accuracy will not be substantially
reduced if it is assumed that the entire equivalent
convection and conduction resistance
of the fin varies
as the film coefficient. If greater accuracy is desired,
test
the fin efficiency may be determined for both
and design conditions using Figs. 5.10 through 5.13
as ‘ápplicable.
e
(5) Compute corresponding value of EMTD+ Isee
para. 5.5).
(6) Adjust all test resistances,as necessary, to correspond to the assumed W+, and compute U>
STEP 5
TOTAL RESIflANCE R&, = R:
The adjusted inside film resistance and equivalent
convection and conduction resistanceof the fin must
be substituted into Eq. (5.35)to determine the adjustedoverallheattransfercoefficient
U: for the
equipment.
.
+ R: + R,’ . . .
.
a
(7) Compute corresponding heat load from
(E)
6
--``-`-`,,`,,`,`,,`---
5.9.4 Computation of Capability. Thermal performQ+ = (U:) (A,) (EMTD+)
ance capability, as defined in this Code, is the ratio
of test capacity to design capacity, where test capacity
(8) Repeat steps (I) through (7)until values of Q+
is the actual flow rateof process fluid the ACHE will
from
steps (2) ’and (7) are equal. Graphical or comhandle at.design conditions of the following:
puter
assistance may be helpful in this iterative so(a) process fluid composition
lution
of W+.
(h) process fluid inlet and outlet temperatures
(9)
Compute
thermalperformancecapability:
.
(c) process fluid inlet pressure
(d) air inlet temperature and density
(e) fan power
PERCENT W A B I L I N =
X 100
The determination of this flow rate, as stated
in
para. 5.1, is an iterative one, since the corresponding
’œ
32
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AIR
ASME PTC 30-1991
COOLED HEAT EXCHANGERS
‘1
T and t are not interchangeable
1.o
0.9
0.8
0.7
0.6
5.0
0.4
--``-`-`,,`,,`,`,,`---
0.3
o.o
0.1
0.2
0.3
0.4
P - Thermal Effectiveness =
FIG. 5.1
0.6
O. 5
’
‘2
0.7
0.8
- ‘1
T1 - ‘1
MEAN
TEMPERATURE
DIFFERENCE
RELATIONSHIPS
Crossflow Unit
1 Tube Row, Unmixed
(Reproduced by permission of Heat Transfer Research, Inc.)
-
33
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0.9
1 .o
A S I E PTC*3O 7 1 E O7576700083267
ASME PTC 30-1991
U
AIR COOLED HEAT EXCHANGERS
T and tare nor interchangeable
0.0
o. 1
0.2
0.3
P
- Thermal
0.4
0.6
0.5
0.7
0.8
0.9
1.o
r? - t l
Effectiveness =
T1 - t l
--``-`-`,,`,,`,`,,`---
FIG. 5.2 MEANTEMPERATUREDIFFERENCERELATIONSHIPS
Crossflow Unit - 2 Tube Rows, 1 Pass, Unmixed
(Reproduced by permission of Heat Transfer Research, Inc.)
34
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Not for Resale
AIR COOLED HEAT EXCHANGERS
ASME PTC 30-1991
T and t are nor interchangeable
1.o
-
0.9
0.8
i
O.7
0.6
0.5
0.4
0.;
0.0
o. 1
0.2
0.3
P
0.4
0.5
--Thermal Effectiveness
=
0.6
0.7
0.8
'2 - tl
T1
- r1
FIG. 5.3 MEAN TEMPERATURE DIFFERENCE RELATIONS;HIPS
Crossflow Unit - 3 TubeRows, 1 Pass, Unmixed
(Reproduced by permission of Heat Transfer Research, Inc.)
35
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0.9
1 .o
7 1 E 0759b78 0883267 4
'ASME
PTC*3O
ASME PTC 30-1991
AIR COOLED HEAT EXCHANGERS
b
R=
T, - T2
rn
Tand tare not interchangeable
f
0.9
0.8
.
0.7
0.6
--``-`-`,,`,,`,`,,`---
0.5
-
I
I
I
0.4
O. 3
0.0
o. 1
O.3
0.2
P
0.4
O.5
- ThermalEffectiveness =
0.6
0.7
'2 - '1
T1 - 'I
MEAN TEMPERATURE
DIFFERENCERELATIONSHIPS
Crossflow Unit - 4 Tube Rows, 1 Pass, Unmixed
(Reproduced by permission of Heat Transfer Research, Inc.)
FIG. 5.4
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0.8
0.9
1 .o
‘ASME PTC*30 91
0 7 5 9 6 7000 8 3 2 7 0
O
AIR COOLED HEAT EXCHANGERS
T,
R=
-
ASME PTC 30-1991
T2
m
T1
T2
fand tare not interchangeable
1.o
0.9
0.7
II
L
O
+-
o
U.
C
0.6
.
d
+-
E
0‘
o
1
0.5
--``-`-`,,`,,`,`,,`---
0.4
O. 3
o. 1
0.0
0.2
.0.3
P
0.4
O. 5
- Thermal Effectiveness =
0.6
0.7
0.8
0.9
‘2 - ‘1
T1
- fl
FIG. 5.5 MEAN TEMPERATUREDIFFERENCERELATIONSHIPS
Crossflow Unit 7 2 Tube Rows, 2 Passes, Unmixed Between Passes
(Reproduced by permission of Heat Transfer Research, Inc.)
O
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I
Not for Resale
1 .o
0 7 5 9 b 7 0 0083273 2
ASME PTC*K3Q 91
ASME PTC 30-1991
R=
m
I
AIR COOLED HEAT EXCHANGERS
T1 - T2
t2
- '1
T2
T and t are not interchangeable
"
--``-`-`,,`,,`,`,,`---
o. 1
0.0
0.2
0.3
0.4
'
'
P - ThermalEffectiveness =
0.5
0.6
0.7
0.8
r2 - r1
T1
- '1
FIG. 5.6 MEANTEMPERATUREDIFFERENCERELATIONSHIPS
Crossflow.Unit - 3 Tube Rows, 3 Passes, Unmixed Between Passes
(Reproduced-by permission of Heat Transfer Research, Inc.)
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(2.9
1 .o
ASME PTC*38 71
O757670 0083272 4 I
AIR COOLED HEAT EXCHANGERS
ASME PTC 30-1991
Tand tare ndt iriterchangeable
1.o
O
0.9
0.8
0.7
0.6
,
--``-`-`,,`,,`,`,,`---
8.
0.5
0.4
0.3
0.0
o. 1
0.3
0.2
P - Thermal Effectiveness =
O
0.6
0.5
0.4
0.7
0.8
t2
tl
7-1
tl
FIG, 5.7 MEAN TEMPERATURE DIFFERENCE RELATlONSHlPS
Crossflow Unit
4 Tube Rows, 4 Passes, Unmixed Between Passes
(Reproduced by permission of Heat Transfer Research, Inc.)
-
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Not for Resale
0.9
1 .o
A S I E P T C x 3 0 71 H O757670 0 0 8 3 2 9 3 b H
ASME PTC 30-1991
R=
AIR COOLED HEAT EXCHANGERS
T1 - T2
t2 - tl
--``-`-`,,`,,`,`,,`---
T and t are not interchangeable
1.o
0.9
0.8
0.7
0.6
O. 5
0.4
0.3
o.o
o. 1
0.3
0.2
P
0.4
O.6
0.5
- Thermal Effectiveness =
O. 7
0.8
0.9
- ‘1
Tl - f l
‘2
FIG. 5.8 MEAN TEMPERATURE DIFFERENCE RELATIONSHIPS
Crossflow Unit 4 TubeRows in 2 Passes, 2 Tube Rows Per Pass, Mixed at the Header
(Reproduced by permission of Heat Transfer Research, Inc.)
-
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1 .o
= 0757670
ASME P T C * 3 O 91
8083274 8
ASME PTC 30-1991
--``-`-`,,`,,`,`,,`---
AIR COOLED HEAT EXCHANGERS
MS
In
c3
Fl
FIG. 5.9
= design station
=
measuring station
SCHEMATIC OF PROCESS FLUID PIPING
41
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out
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,ASME P T C * 3 O 71 E O757670 0083275 T W
ASME PTC 30-1991
AIR COOLED HEAT EXCHANGERS
r
i?
I.
II
P
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--``-`-`,,`,,`,`,,`---
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a
42
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nr
O
0757670 0083276 L
ASME P T C 8 3 0 91
AIR COOLED HEAT EXCHANGERS
--``-`-`,,`,,`,`,,`---
ASME PTC 30-1991
/
C
õ
/f
M
9
/
43
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ASME PTC830 71
O757670 0083277 3 E
. ASME PTC 30-1991
AIR COOLED HEAT EXCHANGERS
r
&
3 I
II
B
9
c
'z
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2
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44
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a
2
r
o
O
'ASME P T C U 3 0 91
O759670 0083278 5
m
AIR COOLED HEAT EXCHANGERS
ASME PTC 30-1991
R
Q
--``-`-`,,`,,`,`,,`---
PP
II
i
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9
N
/
1
45
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D
õ
ASME PTC 30-1991
AIR COOLED HEAT EXCHANGERS
SECTION 6
REPORT OF RESULTS
6.1 COMPOSITION OF REPORT
The test report for a performancetest shall include
the following.
6.1.1 General Information
(a) Identification of the equipment to be tested
(b) Identification of the plant where the equipment
is located
It shall include a statement that the test was conducted in accordance with ASME PTC 30, including
a list of exceptions, if any.
6.1.5 Test Data and Resultsat Operating Condi-
tions. This shall include a listing of the reduced data
for each run after all corrections are applied. It shall
also list a summary of the results at operating conditions.
(c) The name-ofthe owner of the equipment and
his representative atthe test
a¡
(r$ The name of the manufacturer and his repre-
sentativeat the test
(e) A statement of who conducted the test
(0 Date of the test
(s, Date of first commercial operationof the equipment
(h) The design rating and specified operating conditions for the equipment
(i) A statement of the guarantee
O
6.1.2 Object of theTest: This shall tell why the test
is being run and what the parties
to the test are trying
to accomplish.
~.
@
6.1.3 Discussion. This shall include a brief history of
the operation of the equipment and any pertinent
background information; It shall list all prior agreements made with regard to the test.
It shall also discuss any inspection prior to orfollowing the test and state what was inspected and
what was found. It shall describe when andhow the
unitwis last cleaned andits condition during the test.
This shall include a description of any fouling;
6.1.4 Test Methods and Procedures. This shall describe how the test was actually conducted including
any unusual occurrences during the test.
6.1.6 l e s t Result
Adjusted
to Design Condi4ions. This shall list the adjusted test results (adjusted
to design conditions) and compare those results to
the specified performance at design conditions.
6.1.7 Conclusions. This shall be a statement of the
conclusions derivedfrom the test, including whether
or notthe equipment met
its design performance and
the extent to which it exceeded it or fell short.
6.1.8 Uncertainty Analysis. The report shall include
the uncertainty analyses (in accordance with paras.
3.4 and 3.17) for each run.
6.1.9 Appendices. As a minimum the following Appendices shall be included.
(a) Sample Calculation - Thisshallbe included
using the.datafrom one run. It shall illustrate all the
calculations and adjustments that are made to, that
run so that.a reader could start with the data from
any run and makeall necessary calculationsto verify
the resultsof any of the other runs.
(b) LayoutSketches
Thisshall
include adequately dimensioned sketches, both plan and elevation views, showing the location of the equipment
and its relationship to any other equipment orbuildings in the vicinity that would affect air flow. It should
also show wind speed and direction for each run.
-
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AIR COOLED HEAT EXCHANGERS
ASME PTC 30-1991
-
.(c) List of Instrumentation This shall list all the
instrumentationused on the test, including manufacturer and model number.
(d) List of all participatingpersonnel.
(e) Uncertainty AnalysisSample Calculation A
sample calculation for onerun should be included.It
should usethe same run that was used for the results
sample calculation, per (a) above.
6.2.3 Air Densities
(a) Ambient air density
-
--``-`-`,,`,,`,`,,`---
6.2.4 Air
Flow
(i0 Total inlet air flow
- ACFM - ft3/min
- ACFM - ft3/min
- SCFM - ft3/min
(d) Total air flow - Ibm/hr
(b) Total outlet air flow
6.1.10 Raw Data Distribution, At least one complete
set of copies of the signed original log sheets shall
be distributed to each party in the test.
'
(c) Total air flow
6.2.5 Process-Side Conditions
6.2 REPORTDATA
-
As stated in para. 6.1.5 the reduced test data for
each run withall corrections appliedshould be listed
in the report.A list of typical data follows. Since there
are many types of air cooled heat exchangers, this
list is not necessarily comprehensivebut can be used
as a guide. Any other data that
is pertinent to the test
should also be included.
(a) Inlet process temperature "F
(b) Outlet process temperature "F
(c) Inlet process pressure Ibf/ftz
(d) Process pressure drop -across ACHE
(e) Process flow Ibmhr
-
-
-
- Ibf/ft*
6.2.6 Miscellaneous
- air-side - Btu/hr
- process-side - Btu/hr
(c) Fan driver power input per fan - hp
(d) Total fan driver power input - hp
(d Heat load
6.2.1 General Information
(b) Heat load
(a) Run number
(b) Date
(c) Barometric pressure - in. Hg
(d) Ambient dry-bulb temperature- "F
(e) Ambient wet-bulb temperature- "F
(t) Wind speed
mph
@f Wind direction
(e) Uncorrected mean temperature difference- "F
(0 Mean temperature difference correction factor
- "F
-
@ Effective mean temperature difference
(h) Adjustedoverallheattransfercoefficient
Btu/hrftZ*"F
(i) Adjusted process fluid flow rate
ci, Adjusted heat load Btuhr
(k) Capability
%
6.2.2 Air-Side Temperatures
- "F
(b) inlet wet-bulb temperature - "F
(c) Outlet dry-bulb temperature - "F
-
(a) Inlet dry-bulb temperature
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- Ibm/ft3
(b) Inlet air density - Ibm/ft3
(c) Outlet air density - Ibm/ft3
Not for Resale
-
-
- Ibm/hr
OF
-
ASME PTC 30-1991
AIR COOLED HEAT EXCHANGERS
APPENDIX A
.@
0
- TESTING GUIDELINES
A.1 Theactualtestingenvironmentalconditions, the
A.6 Thephysicalinspectionof
the tubebundle
should
include
checking
for
loose
fins, intermeshed
physical condition of the air cooled heat exchanger,
tubes,
bowed
tubes,
and
fouled
or
dirty air-side surand tbe process fluid operating conditions will decide
face.
Some
of
these
may
have
resulted
from cyclic
whether or not a test will beconsideredvalid. In
operation,
process
overheating,
rainstorm
thermal
lordet to enhance the probability of a successful test,
shock, water spray cooling, or improper design for
a careful review and inspection should be conducted
thermal
growth or internal steamout. Defects such as
before starting a full-fledged test.
these will affect performance and should be noted in
the test report.
A.2 All parties to the test must have a clear understanding and agreementof the proposed procedure,
A.7 Check all fan assembliesfor uniform blade pitch,
to beobinstrumentation,andmeaningfulresults
bladeleadingedgeforward,andcleananduncortained. By prior agreement or through discussion at
roded airfoil surfaces. A change in air foil shape will
the site, one person, or a team consisting of one perlikely decrease fan efficiency. Prevent automatically
son from each of the various interests, must be put
variable pitch blades from modulating during the test.
in responsible chargeof the test and subsequent calculations and results.As a first action, it is suggested
that Section 3, GuidingPrinciples,bereviewed so
A.8 Insure that airseals,baffles,tipseals,etc.,as
that disagreements, if any,can be resolvedbefore
originally designed are in place to avoid unexpected
testing.
air leakage.
A.3 Plant operating personnel involved with
A.9 Observe the exchanger in operation,keeping
the air
cooled heat exchanger should be requested
to report
on.performance daily. Ask about maintenance procedures,
on-strearn
performance
characteristics,
process upsets, mechanical problems, and any clues
concerningheattransferperformance.
alert to hot air currents from outside sources or disBy agreement,eliminate
chargeairrecirculation.
these to the maximum extent possible.
A.l O All test personnel should observethe maximum
A.4 A brief preliminary check of the operating proc-
ess flowand temperatureconditionsandair-side
temperatures will help determine if the heat transfer
and pressure drop are reasonably close to expectations. Also, this may point to areas requiring special
attention duringthe equipment inspection before formal testing.
safetyprecautionswhiletakingdata.
Eachperson
must stay within his assigned station to avoid interference or possibly dangerous disruption to other test
personnel. Become acquainted with safety facilities,
escape routes, and alarm systems before undertaking
the test. Be alert to possible physical harm from hot
process streams and discharge air. Insure that all required safety and protective devices, such as fan and
belt guards, are properly installed.
A.5 The process fluid should be sampled and tested
A.ll Steady-stateconditionsaredesirableforthe
to ensure that allof its physical and transport properties are within acceptable limits.
mostmeaningful test results. If test personnel ob49
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ASME PTC 30-1991
AIR COOLED HEAT EXCHANGERS
serve transient test data, they should
alert the test
leader who should decideif testing shouldcontinue,
be stopped, or extended past the agreed-upon time.
should be kept running in order to maintain the full
unit air flow patterns, Potential uneven distribution
of flow of the process fluids mustbe considered, particularly if the process is a two-phase system. This
technique must also result in the inside-tube flow
regime being similar to the original design, ¡.e., laminar or turbulent, the same predicted mechanism of
condensation, etc. Testing in the transition zone between laminar andturbulent flow will not be reliable.
A.12 Interchange of agreed-upon instrumentation
during the test is a good technique to account for
individual instrument error, or to flag significant errors. This is particularly applicable to the measurement of process fluid temperature and pressure at
the exchanger inlet and outlet.
A.13 If process flow and heat load are inadequateto
properly load all of the exchangerbays, it maybe
possible to divert theflòw by valves to a fewer number of bays so that the flow rate and the heat load
per bay are closer to the design point. If this technique is agreedupon, the fans on inactive bays
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A.14 Normally a performance test is run as soon as
possibleaftercleaning.However,
if there is doubt
about the internal fouling resistance, it may be possible to "shock"clean certain processes, while on
stream, using water, steam, or solvent injection.,This
should be arrangedin advance of the test's0 that the
proper operations personnel are available
if it.appears
necessary to investigate the effect of such cleaning.
ASME P T C 8 3 0 71 U O757670 0083283 9
ASME PTC 30-1991
AIR COOLED HEAT EXCHANGERS
APPENDIX B
B.2.2 Tube Bundle
This example is- presented to illustrate a thermal
performancetest of an Air-CooledHeat Exchanger
(ACHE), Due to the large variety of designs and applications covered by the Code, this example is by no
meanscomprehensive.Thesamplespecifications,
contract provisions, data sheets, data,and calculations are not for general application,but may behelpful in formulating similar test procedures for other
ACHE designs and applications.
(a) Number per unit - 1
(b) Nominal dimensions, width X tube- length,
ft- 10 X 24
(c) Design pressure, psig - 100
(d) Number of tube rows - 4
(e) Total number of tubes - 192
(0 Number of tube passes - 4
@
Number
I
of tubes per pass
48
(h) Tube pitch, inches - 2.50 A
(i) Total effective heat-exchangesurface, ftz:
(7) External surface of prime tubes - 1,206
(2) External surface of fins - 23,500
ci, Tube description:
(7) Prime tube
(a) Material Admiralty
(b) Shape - cylindrical
(c) OD,in. - 1.000
(d) ID, in. - 0.902
(e) BWC wall thickness - 18 AW
(2) Fins
(a) Material - Aluminum
(b) Type - Spiral, extruded
(c) Number per in. - 9
(d) Dimension - 2.40in. OD
(e) Root wall ID, in. - 1.000
(0 Root wall OD,in. - 1.160
-
B.l INQUIRY
'0-
An inquiry was issued to manufacturers to quote
anACHE for enginejacket-watercooling:
Fluid to be cooled - clean water Circulation rate, lbm/hr
285,000
Inlet temperature, "F - 168.0
Outlet temperature, O F - 149.0
:Heat load, Btuhr 5,415,000
Inlet pressure, psig 60
Maximum allowable pressure drop, psi - 8.0
Ambient air temperature, "F
94.0
Fouling resistance, hrfP0F/Btu:
. Internal (based on prime insidesurface) 0.001o
External(based on prime outsidesurface) - O
Site elevation - sea level
Barometric pressure, in. Hg 29.92
-
-
-
8.2.3 Mechanical Equipment
(a) Fans
(7) Number per unit
2
(2) Diameter, ft - 8
(b) Gears
(7) Number per unit
2
(2) Type - right angle spiral bevel
(c) Drivers
(7) Number per unit - 2
(2) Type - electric motor
(3) Nominal size,HP - 15
-
B.2SPECIFICATIONS
The following specifications submittedby the successful vendor were accepted and made part of the
contract:
-
B.2.1 General
0
- ACHE
- water cooling
Air flow mode - induced draft
(a) Type of unit
(b) Service
(c)
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-
-
0
EXAMPLE
ASME P T C * 3 O '7%
0759b70 O083284 O M
ASME PTC 30-1991
AIR COOLED HEAT EXCHANGERS
Pertinentprovisions of the contractconcerning
thermal testing were:
(a) The test shall be conducted within six months
after the unit is first placed in .service.
(b) Internaland external heat transfer surfaces shall
be cleaned.prior to the test,
(c) A tube-side fouling resistance of 0.001 hr4tz*"F/
Btu (based on external surface of prime tubes) shall
be used, Fouling on the external surface of the fins
shall be considered zero.
(d) Heatload from measuredprocess-sidedata
(Qi)
shall be used for the test heat load, Heat load
from measured air-side data (Qs))shall be compared
.; If the difference between Q; and Qs) is less
to Q
than 10% of Q;, the test shall be considered valid.
For determination of EMTD, the process-sidedata
and the measured inlet air temperature shallbe used.
The test values of air flow rate and/or exit air temperature shall be adjusted so that Q: = Qp;this adjustment shall be based on the expected accuracies
of these two measurements.
(e) Testing and evaluation procedures shall be in
accordance with the provisions of this Code.
(0 The test overall heat transfer rate shallbe computed from the test data, using Eq. (5.14).
@ For adjustment of the test data to design conditions, Eq. (5.35) shall be used.
(h) For this example the air film is expected to be
the major resistance; therefore, the test value of //h,
shall be established by deducting the summationof
the remaining resistances
from the overall resistance.
(i) The process-side pressuredrop predicted atdesign water circulation rate AP+ shall be computed
from
Ap+
(E?)"""
= (P)
B.4 DATA
Pertinent design and test data are:
Test
=,O00
160.0
141.2
5,207,600
.
.
57.2
6.8
Water circulation rate, Ibm/hr
inlet water temperature, "F
Outlet water temperature, 'F
Heat load, Btu/hr
inlet water pressure, psig
Water pressure drop, psi
Design
285,000
168.0
149.0
5,415,000
60
8.0
Air flow: total Ibm/hr
total SCFM
total inlet ACFM
exit ACFM per fan
Barometric pressure, in. Hg
.Air temp., 'F: Ambient DBT
Ambient WBT
Inlet DBT
Inlet WBT
Exit DBT
578,526
128,561
135,957
72,755
29.92
94.0
75.0
95.0
76.0
134.0
540,692
120,154
127,390
68,459
29.73
91.2
76.7
92.2
?7.3
133.5
Air density, Ibrn/ft3: Ambient
Inlet
Exit
0.07105
0.07092
0.06622
0.07087
0.07074
0.06578
Uncorrected MTD, "F
MTD correction factor"F
Corrected (effective) MTD, "F
Overall heat transfer coefficient:
Btu/(hr4tZ.'F)
Service
Drive-output power perfan, HP
43.23
0.99
42.80
36.60
0.99
36.24
104.91
10.20
119.1 SN""
11.40
i
Note
'
NOTES:
(I) calculated
(2) based on external surface of prime tubes
loads are equal. The
capability will then be computed
from
Percent Capability =
Test Capacity
x 100
Design Capacity
(B.1)
6.5 PROCEDURE FOR CALCULATIONS
Thermal performance capabilitywill be expressed
in terms of test capacity; that is, the actual quantity
of process fluid the ACHE will handle at design conditions of fluid inlet and outlet temperatures, fluid
inlet pressure, fluid composition, air inlet temperature, and fan power.
This will require an iterative or graphical solution,
since test capacity, inside film resistance, and effective mean temperature difference are all unknown.
The test capacity flow rate, W + / will be assumed, and
the heatloadcalculatedindependently
from Eqs.
(5.7)and(5.14).Values
of W+ will be re-assumed
and thecomputationsrepeated until the two heat
The following stepwise procedure is presented to
clarify the order of the performance calculations:
(a) From the test data calculate heat loads from
both process-side and air-side measurements. Compare the two values to determine whetheror not the
test is valid [See para. B.3(dj of this Example]. Adjust
W" to W + so that Q: = Q,.
(b) Compute test value of EMTD.
(c) Calculate test value of
(d) Calculate test values of all resistances, determining air film resistance by difference.
(e) Adjust test air flow rate and test airfilm resistance to designfanpoweranddesign
air density.
v,
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B.3 CONTRACT
ASME P T C x 3 0 71
0757670 0883285 2
ASME PTC 30-1991
AIR COOLED HEAT EXCHANGERS
(0 Assume a value of W+, and compute Q from
Heat balançe check:
Eq. (5.7).
Qi
= (W')
(C.,'
(Tt
- Tz)
(8.2)
O0P
Q",
(g, Computetrialvalue of EMTD, basedon assumed value of W+, (process side) adjustedW + (air
side), and calculated t:.
(h) Calculate adjusted value of inside film resistance. Unless test data differs markedly from design,
Eq. (5.39) may be reduced to
x 100 = 5,406,456 - 5,207,600 x
5,207,600
,oo
= 3.82%
Therefore, test heat balance is within permissible
limits. At this point responsible parties to the test
agreed that exit air temperature measurement was
more accurate than air flow rate measurement; therefore, air temperatures EMTD"
for
calculation were not
adjusted. Process-side heat loadQ i was used forthe
analysis, and measured airflow rate adjusted for heat
balance:
Compute trial value of U: from Eq. (5.35).
ci, Calculate Q+ from Eq. (5.14): Q: = UTA,
(i)
adjusted W" = 540,692
(EMTD),
X
5,207,600
= 520,805 Ibmhr
5,406,456
(U Repeat steps ( f ) through (j) until the values of
Q+ from steps ( f ) and (j) are equal, Graphical or in-
Test EMTD:
terpolation procedure may be used to expedite this
trial-and-error solutionof W+.
'(0 Calculate the capability of the ACHE, using the
equation
W+
percent capability = - x 100
W*
x = 16O.O"F
c = 141.2"F
(B.4j
c=
(m) Calculate the predicted process-side pressure
92.2"F
drop from the equation
APp' =
..(a)
ti = 133.5"F
1.80
(8.5)
LMTD" =
(141.2
- 92.2) - (160.0 - 133.5)
.
In
49.0
26.5
-
= 36.605"F
B.6 PERFORMANCECALCULATIONS
Correction factor:
- t2 - ti
Tl - tl
= (277,000) (127.89
- 109.09) = 5,207,600 Btu/hr
R = - Tl
t2
Q," = wOcPaAto
- 92.2 -- 0.6091
- 92.2
- T, -- 160.0 - 141.2 = 0.4552
- tl 133.5 - 92.2
F = 0.99
(B. 7)
= (540,692) (0.2421) (1 33.5 - 92.2) = 5,406,456 Btu/hr
EMTD" = 36.605
53
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= 133.5
160.0
Not for Resale
X
0.99 = 36.24"F
--``-`-`,,`,,`,`,,`---
Test heat load:
ASME P T C * 3 O 91 W 0 7 5 9 6 7 0 ODt1328b 4
m
AIR COOLED HEAT EXCHANGERS
ASME PTC 30-1991
Unadjusted test U:
Inside film resistance = -
5,207,600
c =(A,)(EMTD")
-QZ. - (1206)(36.24)
= 119.15 Btu/hr.ft2"F
= 0.0007361
-.
Test process fluid film resistance:
Inside fouling resistance = (Rp,)
hrft2."F/Btu
(2)
=
0.001 O000 hr.ft2*OF/Btu
[see para. B.3(c)]
(E$$) (
Outside fouling resistance = (Rto)(:)
'
ki = 0.386
Btu
hrft'*("F/ft)
[see para. B.3(c)l
Dq = 0.902/12 = 0.0751 7 ft
v,.
=
Prime. wall conduction resistance= A r In (rPJp,)
2 T L N kpw
277,000
= 21,256 Whr
(48)(~/4)(0.902/12)~(61
.I 8)
p i = 61 .I8
Ibm/ft3
=O
For the configuration used in this Example the preceding equation reduces to:
Prime wall conduction resistance
'
=
rpo In (rp,lJp,)
kPw
Ibm
p; = 0.455 X 2.42 = 1,1011 -
0.50
0.50
hrft
-In - 12 0.451 =. 0.0000672 hrft2."F/Btu
64
cip= 1.O0 Btu/lbm
OF
Ibm
piw = 0.480 X 2.42 = 1.I61 6 -
Bond conduction resistance
= 0.0000100 hrft2*"F/Btu (from manufacturers' data)
,
hrft
h; =
1
21,256 X 0.0751 7
(
X
Fin root wall conduction resistance = Ar In (rR,lrRlj
2.rrLNkR
61.18
1.101
0.07517
I .I 01 I
X
0.386
Simplifying, = rRIIn (rRJrR)
I
kR
(I1.1616
,101 I)'.'~
-
= (0.11811) (9091.7) (1;4133) (0.9925)
= 1506.2 Btu/hr.ft2eoF
54
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0.58
0.50
In l2
= 0.0000529 hrftZe0F/Btu
117
ASME PTC 30-1991
AIR COOLED HEAT EXCHANGERS
Trial-and-error solutionfor W + :
Equivalentconvectionandconductionresistance
of the fin =
Trial No. 1: assume W + = 288,000 Ibm/hr
- 0.0000000
- 0.0000672 - 0.0000100 - 0.0000529
0.0007361 - 0.0010000
"
119.15
(288,000) (1.00) (168.0- 149.0)
Q'
= 5,472,000 Btuthr
= 0.0065266 hr&."FIBtu
Ata = 5,472,000/(502,012
t2 =
rl
+ At,
= 95.0
X
+ 45.02
Summary of unadjusted test resistances:
... .. .. . ...,,..,...,...,,..0.0007361
..,. .....,..,........ .......0.001 O000
.. .....,........ .......O.OOOOOOO
.... ... .... .....,.............0.0000672........ ... . .......,,...,....... 0.00001 O0
.. . .........................0.0000529
...... ......................... ...0.0065266
inside film , , ., .
inside fouling
outside fouling.. ,,
prime wall
,
bond ,
,,, ,
fin root wall.. , .
air film
,.
Trial EMTD =
In
Z R = 0.0083928
y = IER
(149.0 - 95.0)
X
0.240) = 45.02"F
= 140.02"F
- (168.0 - 140.02)
54.0
27.98
1
0.99 = 39.18"F
Adjusted inside film resistance:
R
: = 0.0007361
= 1/0.0083928 = 119.15 Btu/hrftz*"F
(-)""
= 0.0007135
Summary of adjusted test resistances:
.
.. .
.
.
.... .. ... .. .. ..
. .. . .. ... .
... ... . .. .. . . . ... .. ...
.. ... ....... .. . . ...
. . . ... . .. . .. .
............0.0007135
inside film ....................
inside fouling ..., ..,........ ........ ..0.0010000
outside fouling.. . ... . ... .. ..O.OOOOOOO
prime wall ... .., .., .. ....... .....0.0000672
bond . ... ... .. . . . . . ,. 0.00001 O0
fin root wall. ... .
.. .. . .. .0.0000529
air film ,... .. .... . .... .. .... .. .0.0066917
Adjusted test airflow rate:
(z) ($
10.7
W+
= W"
U3
SR = 0.0085353
=520,805(Er(-)
= 502,012
Ibm/hr
U,? = IER = 117.16
NOTE: The value Qf W" in this calculation is the test airflowrate
adjusted for heat balance.
Q+ = (11 7.16) (1206) (39.18) = 5,535,960 Btu/hr
Trial No. 2: assume W+ = 290,000 Ibm/hr
Adjusted test airfilm resistance:
Q' = (290,000) (1.00)(168.0
= 5,510,000 Btu/hr
= 0.006691 h~fP"WBtu
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213
ASME PTC830 91
= 0759670 0083288 8
--``-`-`,,`,,`,`,,`---
AIR COOLED HEAT EXCHANGERS
ASME PTC 30-1991
EMTD = 38.98"F
Afa = 5,510,000/(502,012 x 0.2421) = 45.33"F
t2 = 95.0
Trial EMTD =
+ 45.33
1
In
X
=
140.33"F
Adjusted R,+ = 0.0007361
1
54.00
27.67
;;;,:::r
(-
=
Adjusted :
U
0.0007096
U:
= 11 7.22
By interpolation, W+
W+
W*
Percent Capability =-
= 117.21
= 290,022 Ibm/hr
X
100
=-290'022
285,000
Q+ =
= 0.0007095
Q+ = (117.22) (1206) (38.98) = 5,510,498 Btu/hr
Adjusted ZR = 0.0085314
Adjusted
-
Adjusted ZR = 0.0085313
0.99 = 38.98"F
Adjusted R;' = 0.0007361
(;;;,Er
x 100
=
101.76 %
(117.21) (1206) (38.98) = 5,510,231 Btuhr
Process-side pressure drop:
Trial No. 3: assume W + = 290,022 Ibm/hr
Af'l'=
Q+ = (290,022) (1.00) (19.0) = 5,510,513 Btu/hr
Ata = 5,510,513/(502,012
t2 = 95.0
X
e)
= 6.8( 285 O00
= 7.1 6 psi
0.2421) = 45.34"F
Since the allowable pressure drop (as stated in the
inquiry) is 8.0 psi, the unit passed the pressure drop
criterion.
+ 45.33 = 140.34"F
56
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ASME P T C * I O
91
-
0759670 8083289 T
ASME PTC 30-1991
AIR COOLED HEAT EXCHANGERS
--``-`-`,,`,,`,`,,`---
APPENDIX C
- EXAMPLE UNCERTAINTY ANALYSIS
C.2 DEFINITION OF LETTER SYMBOLS
ThisAppendixprovidesanexampleuncertainty
analysis for an Air Cooled Heat Exchanger (ACHE),
using the methodology describedin ASME PTC 19.11985. Theexample is for apost-testuncertainty
analysis, using the designandtestvalues
forthe
enginejacket-watercoolerexampledescribed
in
Appendix B.
Special letter symbolsareused in this Appendix
which do not appear elsewhere ip the Code. The definitions for these symbols are:
Bij = the upper limit of the bias error for parameter ]
Sij = the precision index for parameter j
t,,,, = the Student4 statistic,determinedfrom
tabular data for a degrees of freedom, v,
and a 95 percent coverage
= the overall uncertainty
of result, r, for a 95
percent coverage
= the degree of freedom for parameter i,.
used in.evaluating the precision error
3 = sensitivityfactor which functionallyrelates a change in an independent parameter ] to the change in the result
C.1 SUMMARY OF ANALYSIS APPROACH
@
The exampleuses
the following step-wiseapproach, as prescribed in para. 4.2 of PTC 19.1:
(a) Define MeasurementProcess. The equations
used in computingsthe test results àre listed. From
these equations, the independent measurement parameters are identified. These equations also provide
the basis for developing the sensitivity factors for
each parameter. The sensitivity factorsare the functional relationships betweeneach independent measurementparameterand the testresult.
. (b) Calculate Bias and PrecisionError Estimates. The
bias and precision error estimates are determined
for
each independent parameter. Typical values
for each
bias and precision error estimate are providedin this
example, The analysis procedurefor developing these
values is not demonstrated in this example, but is
addressed in great detail in PTC 19.1,
(c) Propagate the Bias andPrecisionErrors. Using
the sensitivity factors and thebias and precision values for each independentparameter, the biasand
precision errors are propagated separately.
(d) CalculateUncertainty. The bias andprecision
errorsandcombined
into an overalluncertainty
value,
C.3 DEFINEMEASUREMENTPROCESS
Thereare two results calculated for the test example in Appendix B - Capability and Process-Side
Pressure Drop. The development of sensitivity factors
for each of these results will be illustrated.
C.3.1 Capability. Theequationsused
Recalling that the process-side heat load, Q; , was
used for the analysis, the following are the calculations for capability:
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I
to compute
capability in Appendix B are repeated herein.
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ASME P T C * 3 0 91
m
0757670 U 0 8 3 2 9 0 b
m
AIR COOLED HEAT EXCHANGERS
ASME PTC 30-1991
EMTD" = 0.99
X
(C - t3 - (C -
R, = Inside Film
(c,2)
+ inside Fouling + Outside Fouling
+ Prime Wall + Bond + Fin Root Wall + Air Film
From Appendix B
NOTE: A constant value of 0.99 is used for the Temperature Correction Factor, F. Referringto Fig. 5.7 for the test conditionsof the
Temperature Difference Ratio,R, and the Thermal Effectiveness,P,
the value of F is nearly constant at 0.99 over a wide range of P
and R values.
RT = R',
+ 0.0010 + 0.0000 + 0.0000672
+ 0.00001 + 0.0000529 + R:
RT
+ R: + R: + 0,0011301
n o
U;
$'=
=.
- - 0.0007361 - 0.0010000 - O
R,'
I
+ Rp+ + 0.001 1301
(C.12)
U,"
- 0.0000672 -
0.0000100
- 0.0000529
(C.13)
'
R,"=--
0.001 8662
U:
(C.4)
CAPABILITY (%) =
NOTE: The other calculated resistancevalues, (0.0018662 = the
sum of the resistancesof the inside film, inside fouling. prime wall,
etc,) are taken as constants because of the negligible changes in
thesevalues
for theexpectedmagnitudes
of themeasurement errors.
R: =
R'(5)
0.681
I
($) 1O0
X
(C.14)
The next step is to identify the independent parameters which appear in the preceding equations, and
then to develop a setof equations which functionally
relate the independent parameters to the Capabiiity
(Le., determine the sensitivity factors). Thefirst part
of this task is accomplished by simply listing all the
parameters which appear in the equations, and eliminating all constants and all calculated parameters.
All
design values are considered constants for the purpose of the uncertainty analysis.
In reviewing the remaining parameters, it is.necessary to ascertain if all of these parameters are, in
fact, independent. To do this, it is necessary to review
the calculationsandcorrections, if any, thatwere
used in determining these values. In this case, the air
flow rate, wo, is found not to be an independent parameter. The air flow rate was determined by a velocity traverse at the discharge of each of the fans;
however, by agreement, the mass flow rate of the air
wasbased on a heat balance calculation for use in
this comcomputing the test results. The equation for
putation was
0.8
R',
= R'(")W+
(C.15)
(Cl 1)
58
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I
~~
. -
~
~.
ASME PTCs30 93
OLED
AIR
--``-`-`,,`,,`,`,,`---
e
rn
0759b70 0083293 8
ASME PTC 30-1991
HEAT EXCHANGERS
The final list of independentvariablesthenbecomes:
TG T;, W, WBT;,
t,' g, hp",and B".
As described in para. 2.7 of PTC 19.1, the sensitivLikewise,
therelative(dimensionless)sensitivity
ity factorcanbedeveloped
in either of two ways:
(a) When there are known
mathematical
relationfactors, etApmand
are
determined
by
P
ships betweenthe result and the independent paramcomputed
beeter,
sensitivity
can
factors
the
6AP,'/AP,'
analytically by partial
differentiation
of the
equations.
efmp'p= 6A P J A c = 1
(b) When no mathematical relationshipis available
or when differentiation is.difficult, the sensitivity facdetermined
becan
numerically
tors
by taking finite
SAP;JAP,'
e;, = 6W/W = - 1 . 8
increments of each of the parameters and determining the effectof the incremental changeon the result
by using the data reduction calculation procedure.
For the Capability calculations, mathematical reC.4 DETERMINETHEBIAS AND PRECISION
lationships are established, as demonstrated by the
ERRORS
listed equations; however, thereisno closed solution
for these equations. The result must be determined
Tables C.2 and C.3 provide listings of the bias errors, the precision error estimates, and the degrees
by an iterationschemebetween
Eqs.
(C.7)
and
of freedom associatedwith each independent param(C.? 3). As a result, it is more practical and convenient
eter used in computing the capability and the procto use anumericalsolutionapproach
in this case
ess-side
pressure drop. As described previously, PTC
(assuming thereis access to a co-mputer).
19.1 provides detailed instructions on the determiThe numerical development of the sensitivity facnation of the error terms. The values providedin Tators for each of the independent parameters are probles
C.2 and C.3 are values which could typically be
vided in Tables C.1a and C.l b. For each independent
achieved
usingtheproceduresandmethods
deparameter, positiveandnegativeincrementsare
scribed
in
this
Code.
The
uncertainty
values
and
the
added to the testvalues, with the incremental values
degrees
of
freedom
associated
with
the
precision
inbeing approximately equalto the expected precision
dices are based on the assumption that a computerand bias error values, Capability is determined stepbased data acquisition system, with system accurawise foreach incremental change. The sensitivity faccies
in accordance with Section 4, was used to actor for each parameter is calculated as the change in
quire
the temperature data andthe measurement of
Capability divided by the positive or negative increprocess
flow rate,Theotherdata
- air flow rate,
mental value. Positive and negative incremental valbarometric pressure,fanhorsepower,andprocessues are usedto determine the degreeof non-linearity
side pressure drop - were acquired manually using
in thesensitivityfactoraroundthetestvalue.
instrumentation of the accuracies specifiedin Section
The Table results show the
final solution for each
4. Thedegrees of freedom, which aredetermined
parameter.
from the numberof readings and the number
of measurement points, are based
on a typical one-hour
test.
C.3.2 Process-Side Pressure Drop, The equation for
It should be emphasized that the values for precithe calculation of the process-side pressure dropis
sion and bias error for each of the independent pa;
rameters listed in TablesC.2 and C.3 are the result
(C.? 6)
ofpropagating all the identifiableelementalerror
sources. These values are provide$ for example purposes only. The actual bias and precision error values
In this case, there is a convenient mathematical
aredependent on theparticular ACHE tested, the
relationship between the result, AP.,, and the indenumber and typeof instruments, the calibration propendent parameters, AP' and W4 The absolute (dicedures used, the length of thetest, the constancyof
mensional)sensitivity factors, ,aredetermined by
the test conditions, and the ambient conditions at the
time of the test.
partial differentiation of Eq. (C.16) by
O
a
o
O
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-ASME P T C * I O
91 E 0759670 0083292 T E
ASME PTC 30-1991
--``-`-`,,`,,`,`,,`---
AIR COOLED HEAT EXCHANGERS
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ASME P T C * 3 O 71 W 0757670 0083274 3
ASME PTC 30-1991
’
AIR COOLED HEAT EXCHANGERS
TABLE C.2
ERROR ESTIMATEVALUES FOR CAPABILITY
of Freedom
Sensitivity
Factors
Bias limit
Precision
Index
Degrees
(Bi 1
(Si 1
(v)
(0) [Note (111
0.006
0.013
0.25
0.63
59
58
59
W
0.05
0.1o
2.5
0.25
0.25
0.3
0.2
0.08
Bo
0.01
0.012
4.61 14
6.3521
1 .O229
1.7590
0.0392
0.0523
2.5141
1.7629
Parameter
T
c
W
t;
’
WBT
e
58
58
56
7
3
0.50
0.47
’
NOTE:
(1) Reported from Tables C.la and C.l b.
C.5 PROPAGATETHEPRECISION AND BIAS
ERRORS
Evaluating Èq. (C.18) with the values in Table C.2,
14
x 0.006)2= 0,000766
Si, : (6.3521 x 0.013)’ = 0.006819
siw : (i.0299 X 0.25)~= 0.066293
Sip, : (1.7590X 0.63)2= 1.228041
SiwBq : (0.0392 x 0.50)2= 0.000384
Si., : (0.0523 X 0.47)’= 0.0006ó4
Sihp.: (2.5141 X 0.08)2 = 0.040452
Si, : (1.7629 X 0.012)’ = 0.000448
XSi’ = 1.343807
Si-,, = ‘1.I 592
Si, : (4.61
C.5.1 Capability. The bias limit of the result, Bicap,
is computed using the equation
Evaluating Eq. (C.1 7)with the values in Table C.2,
Bi, : (4.61 14
X 0.05)2 = 0.053163
Bi, : (6.3521 X 0.10)2 = 0.403492
Bi, : (1.0299 x 2.5)’ = 6.629338
Biti : (1.7590 x 0.2512= 0.193380
BiwBq : (0.0392 x 0.25)’ = 0.000096
Bici : (0.0523 X 0.312= 0.000246
Bihp. : (2.5141 x 0.21’ = 0.252828
Bi, : (1,7629x 0.01)2 = 0.000311
F:
7.532854
Bicep = 2.745
(C.19)
The precisionindex of theresult, Sicap, is computed using the equation
rN
Applying the values of Table C.2 to Eq. (C19 )
1
(C.18)
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XBi2
Since not all the degrees of freedom given in Table
C.2 are greater than 30, the degrees of freedom for
the result,ucap,are computed accordingto the WelchSatterthwaite formulas, as
ASME P T C 8 3 0 91 W 0757670 0083295 5 W
ASME PTC 30-1991
AIR COOLED HEAT EXCHANGERS
TABLE C.3
ERROR ESTIMATE VALUES FOR CAPABILITY
Bias Umit
Parameter
W
Ae
(Bi 1
Precision Index
(Si 1
2,s
0.05
1.7
0.063
Degrees of Freedom
Sensitivity
Factors
(4
(e)
59
1
11
1.a
N
28
!!
1-1
= 0.02631
v/
- 69
1.8058
0.02631 -
v*=
Evaluating Eq. (C.21) with the values in Table C.3,
C.5.2 Process-Side Pressure Drop. The relative bias
limit of the result, Biu; is computed using theequation,
SÍD; =
[
ln
SÍ,+
B( =
Si,+
Bi,
=
[
(1
(1.8 X
F)]
= 0.0238
= 7.16
0.0238 = 0,170 psi
X
i
The degrees of freedom of the result, uAP+,,is determined usingEq. (C.19)and the valuesin Table C.3
Evaluating Eq. '(C.20) with the values in Table C.3,
BÍ,:
+
(1 X 0.017)'
as,
a)]
1fl
X 0,025)2+ (1.8
X
= 0.0283
v + =
= 38
ApP
(1xo.o17)4 I
59
'
11
From Appendix B,
C.6 OVERALL UNCERTAINTY VALUES
AP; = 6.8 psi
The overall uncertainty in the result for a 95 peris defined by,
cent coverage,
Up= 7.16 psi
BÍ,+ = 0,0283.
Un,,,,
P
= [Bi2,
+ (tSi,)2]1n
(C.22)
The overall uncertainties
are evaluated accordingly,
O
-
or, Bi&; = BÍ&,+ x AP;
= 0.0283 x 7.16 = 0.202 psi
The relative precision index of the result, Si,,;
ucap,Rss=
[2.745a + (2
U,P+,,~ = [0.202'+ (2
computed using
63
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X
1.1592)2]1'2= 3.59 percent
is
Not for Resale
X
0.1 70)']ln = 0.395 psi
.ASME P T C * 3 0 71 E 0757670 0 0 8 3 2 7 b 7
ASME PTC 30-1991
EXCHANGERS
HEAT
m
'
AIR COOLED
TABLE C.4
TWO-TAILED STUDENT4TABLE FORTHE 95 PERCENT CONFIDENCE LEVEL
Degrees of
Freedom
Degrees of
Freedom
t
1
2
3
4
5
12.706
4.303
3.182
2.776
2.571
18
19
20
2.120
2.110
'2.101
2.093
2.086
6
7
8
9
10
2.447
2.365
2,306
2.262
2.228
21
22
23
24
25
2.080
2.074
2,069
2.064
2.060
11'
12
13
14
15
2.201
2.1 79
2.1 60
2.145
2.131
26
27
28
29
30 or more use
2,056
2.052
2.048
2,045
2.0
16
17
to + t the area included is 95%.
where the value of the Student-f statistic, t, is determined from tabular data for the degrees of freedom
(70 for capability and
38 for AF';), and fora coverage
of 95 percent (see Table C.41,t'is equal to 2.
The results ofAppendix B example are stated as
follows:
E S T CAPABILI'IY =
101.8
percent
k3.6
percent
and,
APp' = 7.16 psi k0.41
psi
As discussed previously, the Appendix B example
indicates a contractual specification that the air flow
rate, used in the calculations of the test capability,
would be determined using
a heat balance calculation
as defined in Eq. (C.15).Presumably, such an agreement would be based on
a preliminary uncertainty
analysis. As a check of this approach, an uncertainty
analysis was also conducted based on using the measured air flow rate (Le., the air flow rate calculated
from the exit air velocity traverses)in the calculation
of thetest capability.Theresults
of thisanalysis
yielded
TEST CllPABILlN = 103.4 percent -k4.0 percent
64
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GENERAL NOTE: Table gives values o f t such that from - t
t
ASME P T C * 3 O 91
O759670 0083297 9
AIR COOLED HEAT EXCHANGERS
ASME PTC 30-1991
APPENDIX D
SPEClAL CONSIDERATIONS FOR COMPUTATION AND
ADJUSTMENTOFRESULTS
I
D.1 INTRODUCTORY COMMENT
'
The adiustmentoftube-side heat transferandpressure drob data taken during a test compared to the
design conditions is complicated by the many different combinationsof flow regime, heat transfer process and streamcomposition that canexist on the tube
side. The common case of single phaseturbulent flow
is dealt with in paras. 5.9.2 and 5.9.3. But laminar
flows and iondensing applications require different
correlations and particularly greater attention to the
details of the problem, an_dthis Appendix offers some
guides for analyzing these problems. For some of
cases encountered, particularly in the process industries, more complex,
usually
computer-based,
procedures
are
required.
Some
of these cases
are
identified below and references to the pertinent literature are given.
D.2 FLUIDWITH NO PHASE CHANGE
D.2.1 Pressure Drop. Pressure drop due to friction
for single phase flow inside tubes may be estimated
from the Moody-Darcy friction factor chart(Ref. 1811,
.given hereas Fig. D.l The pressure drop due to friction, APf, is related to the friction, factor, fM, by
The abscissa of Fig. D.l is the Reynolds number of
the tube-sidefluid:
In turbulent flow, it is necessary to take wall roughness into account. New tubesmay be considered
smooth, and a good representation
of that curve over
the Reynolds number range from 10,000 to 100,000
is credited to Blasius (Ref. 191) and given here as Eq.
(D.3):
Older tubesmay be considerablyroughenedby
corrosion or depositsand
relative roughness up
to €/Dj= 0.003 may be encountered in practice.
For flows that would normally be laminar, various
types of twisted tapes, springs and solid cores may
be inserted into the tube in order to disturb theflow
and increase the heat transfer rate. The devices are
variously termed turbulators, retarders, or accelerators, and they inevitably increase the pressure drop
also. There are no general correlations applicableto
all geometries, and the manufacturer of a particular
devicemustusuallybereliedupon
to supplythe
pressure drop and heat transfer correlations.
An additional pressure drop is encountered at the
entrance to the tube due to the increase in kinetic
energy of the fluid and the frictional losses associated
with the expansion from the vena contracta and the
formation of the fully-developed velocity profile. A
reasonable estimate of this loss is 1-1/2 to 2 velocity
heads for eachpass,based
on the velocity in the
tubes:
):(
APent=. n
03.4)
The region of discontinuity (Re; from 21O0 to about
7000) betweenthelaminarand
turbulent regimes is
where n = 1.5 to 2 and APentis entrance pressure drop.
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@
highly unpredictable and is very strongly influenced
by entrance disturbances and flow maldistribution.
ASME PTC 30-1991
AIR COOLED HEAT EXCHANGERS
W
O
r
T.
N
O
t-
66
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er
g
ASME PTC 30-1
AIR COPLED HEAT EXCHANGERS
The total tube-side pressure drop
is the sum of APf
and APent. Nozzleandheaderlossesmayneed
to be
separately considered.
.The properties used in these equations and those
in the following paragraphs are usually evaluated at
the arithmetic mean bulk temperature on the tube
side, except for pp,,, which is evaluated atthe inside
wall temperature at the
point where thefluid reaches
its arithmetic mean bulk temperature.
991
For fully developed turbulent flow (Rei > approximately 7,000), there areseveralgoodcorrelations
available. For general use, the Petukhov-Popov equation,Eq.(D.61,(Ref.
[I 311, is regarded as .the most
accurate but it is not in convenient form for ratioing
changes in velocity, for example,
--``-`-`,,`,,`,`,,`---
0
D.2.2 Heat Transfer. The appropriate heat transfer
correlation to use depends upon whether theflow is
turbulentorlaminar. For laminar flow (Rei c 2100),
many different 'correlations and analytical treatments
have been given in the literature. Reference [ I O ] is
the most comprehensive.and up-to-datesource. The
where the subscript t indicates turbulent.
Hausen equation (Ref. [Ill, [I211 is widely recommended in the literature to represent the major efTheviscosityratioterm
hasbeenadded to the
fects in laminar flow:
above equation here. The Moody-Darcy friction factor, fM,in Eq. (D.6) can be calculated from Eq. (D.3).
0.0668(
3.65
+
,+o.o4[
y)(
y)(
F)
(?)(y)(?)]
.(E)"'
a
TheSieder-Tateequation,
Eq. (D.7),Ref.[4],
is
usuallyadequate for air cooler applications and
is
more convenient for adjustments of tube side conditions:
from Kern
Forwater, Figs. D.2aandD.2btaken
(Ref.[141),are very easy to use.FiguresD.2aand
D.2bmayberepresented
by the following dimensional equation:
(D.5)
where fi,,Lis the mean inside heat transfer coefficientforlaminar flow in atube of length L.
Examination of Eq. (D.5)reveals thatforsmall
L, 6 is proportional to L"/3, where L is the length of
0
where (h,),.
the tube. This is due to the development of an adverse temperature gradientas a resultof the conductive heat transfer in the fluid. As mentioned above,
various devices may be inserted
into the tube in order
to break up this gradient by disturbing the boundary
layer or by fdrcing theflow tobecome turbulent. No
general correlations are available for
all such devices,
and specific correlations for eachtype should be obtained from thevendorandtheirinterpretation
agreedupon prior to thetest.
I .70 (loo
and C = 0.911
+ T ) V;,
-
. ,
0.429 log,,D,
(D.8b)
(D&)
where T is the mean water temperature in "F, V,, the
tube inside water velocity in feetpersecond,and
Dlthe inside tube diameter in inches.
The dimensions of hi are then Btu/hr.ft*."F, and h;
is based upon the inside area of the tube.
67
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ASME PTC 30-1991
AIR COOLED HEAT EXCHANGERS
For transition flow (2100 < Re,
7,000), no accurate predictions are possible because of the slowness with which fully-developed velocity and thermal
profiles are achieved and becauseof the strong effect
of the entrance flow geometry. An estimate can be
made by linearly interpolating between the laminar
flow heat transfercoefficient,
,obtainedfrom Eq.
(D.5) and the turbulent flow result, h,, , obtained
from Eq. (D.6) or (D.7)) using the equation:
h, = KL t (h,,, - 7j;.L I(
Re'
-
APP,TPF
- 2100
4900
)
for 2100 c Re,< 7000
(D,10)
= 43P,,Y
where TPF indicates two-phase flow and APp,v is the
pressure dropcalculatedfrom
Eq. (D.?)
assuming
that theflow is all vapor and no,condensation occurs.
The mean two-phasemultipying factor, P,,,is read
from Fig. D.3 as a function of the exit qualityand the
reduced pressure of the vapor,
0.9)
Any calculation in this range must be regarded as
highly uncertain.
J
P
P, = -
(D.11)
PC,
where P is the absolute pressure of the condensing
vapor and PCr is the absolute critical pressure of the
vapor being condensed. P and P,, must be in consistent units, usually psia.
The other two pressure effectsthat need to be considered in condensation are the momentum and hydrostatic contributions. Momentum
effects arisefrom
the deceleration of the vapor as it condenses; in principle, this results in a pressure 'recovery. However,
this recovery is usually at least partially offsetby increased friction losses in the liquid film. ln design, it
is usually conservativeto neglect any pressure recovery that may occur. However, in analyzing the performance of aunit,
this pressurerecoverymay
explain, at least partly, why the pressure drop is less
than that expected.
The hydrostatic pressure effect arises only for vertical or inclined
tubes. The hydrostatic pressure effect
results in an increase in the pressure atthe lowerend
of the tube.compared to a similar horizontal tube.
Accounting for this effect requires detailed calculations of the local density of the two-phase mixture
and is often(conservatively) omitted in condenser
design.
D.3 SINGLE COMPONENT CONDENSATION
-,
D.3.1 GeneralComment. The condensation of a
single (pure) component can usually be considered
to be carried out at nearlyconstantpressureand
therefore at nearly constant temperature. However,'
the details of the condensation process are not fully
understood, and the correlations correspondinglyare
not very precise, Coefficients for condensing steam
or ammonia are so high (in the absence of non-condensablegas) that this uncertainty hardly matters.'
Howbver,coefficients for other substances(such as
propane or other light and medium hydrocarbons),
while generally quite good, may be, comparable to
the air side when the area ratio is taken into account.
The heat transfer correlations givenbelow are accurate enough for most purposes. Prediction of pres-,
sure drop in two-phase flow is very uncertain; errors
up to a factor of five are possible.
D.3.2 Pressure Drop. Pressure drop calculations in
two phase flows in principle require thestep by step
integration of local conditions, coupledwith the heat
transfer rate to estimate the rate at which the vapor
is being condensed. The total pressure effect is the
algebraic sum of the frictional, momentum, ,and hydrostatic effects, of which the first is usually of the
greatest concern. Animportant parameter is the quality ofthe flow, which is defined as the mass flow rate
of the vapor phase only, divided by the total mass
flow rate of both vapor andliquid phases. A saturated
D.3.3 Heat Transfer Coefficients
D.3.3.1 Horizontal Tubes. At low condensing rates
inside horizontal tubes, the condensate flows down
the wallsof the tubeinto a pool at the bottom of the
tube, which then drains by gravity out of the end of
68
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--``-`-`,,`,,`,`,,`---
i
vapor with no liquid present has a quality of 1.00,
and a totally condensed stream at its boiling point or
bubble point has a quality of zero.
Estimates can be made of the frictional loss using
the work of Martinelli andNelson (Ref. [151). The
the confrictional pressure dropthrough the tube for
densing flow entering as a saturated vapor(x, = 1.O),
and exiting at a qualityof x, is found from
AIR
COOLED HEAT EXCHANGERS
30-1991
ASME PTC
--``-`-`,,`,,`,`,,`---
1 .o
1.5
3
2
4
6
5
7
8
9 1 0
Velocity Through Tubes, ft/sec
GENERAL NOTE: This chart applies only to a tube 0.62 inside diameter
For other diameters, refer to Fig. D.2b.
FIG. D.2a
3/4 in. X 16 BWG).
CHART FOR CALCULATINGIN-TUBEHEATTRANSFERCOEFFICIENTS
FOR WATER
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AIR COOLED HEAT EXCHANGERS
ASME PTC 30-1991
1.2
'i *I
ò
5 1.0
U ,
.-
0
CI
E0 0.9
ò
-.o"
O.7.
0.5
0.4
0.6
0.7
0.8 0.9 1.0
1.5
2.0
Inside Diameter of Tube, in.
GENERAL NOTE: Multiply the value obtained from Fig. D.2a by the above factor.
. .
FIG, D.2b
CORRECTIONFACTORTO
FIG. D.2a FOROTHERTUBEDIAMETERS
the tube. Kern's modification (Ref. [I411of Nusselt's
equation (Ref. 1161) may be used to calculate the
coefficient in this case:
In this equation,
r
i
113
L
-I
and ß is found as a function of I$? in Fig. D.4. The
Chaddock correlationcorrectsthehorizontaltube
Nusselt equation for the relative amount of surface
blanketed by thestratified pool of liquid (through
which no heat transfer is assumed to occur).
At higher condensing rates, all or a portion of the
tube may be in annular two-phase flow, in which a
turbulent liquid film covers the entire inner surface
of the tube. A convenient correlation forthis regime
is due to Boyko and Kruzhilin (Ref. [18J).
L is the length of the tube and W ,
is the pounds of vapor condensed pertube per hour.
If a U-bend tubeis used, L is the combined lengthof
both straight sections and the U bend.
A more rigorous equation used for
low condensing
rates is the Chaddock correlation (Ref. [I 71):
(D.14a)
In this equation, G, is the mass velocity of the condensing stream
where,
r
=
I
- 5.06
I
70.142
X
10-4
L
)LrT,,,
-7-J"'
D:.75
(D.13b)
-I
r
1114
L
J
where W,, is the pounds of vapor entering each tube.
per hour.
70
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ASME PTC 30-1991
AIR COOLED HEAT EXCHANGERS
Asthe condensing load increases above the point
at which thecondensate film becomes turbulent
i
the
(which occurs when Re, = 4W, l p L P ~ D>2000),
Colburncorrelation (Ref. [20]) becomesvalid.The
Colburn correlation may be represented graphically
as in Fig. D.5 or analytically by Eq. (D.16):
Also,
--``-`-`,,`,,`,`,,`---
where x, and x, are the inlet and exil qualities of the
stream,. 'respectively, For the special and important
case of totalcondensation of asaturatedvapor
stream, the term in brackets in Eq. (D.14a) reduces
to:
where Pr,,p =
kf,P
Again, research is showing that the transitionfrom
laminar to turbulent flow is not as abrupt as,suggested by Fig. D.5 and the actual coefficients in the
transition regime are higher than shown for Rei from
perhaps 800 to 3000.
If the condensing load (or moreexactly, the vapor
flow) is sufficientlyhigh, vapor shear effects cause an
early transition to turbulence in the condensate film
and a sharp increase in the heat transfer coefficient.
Undertheseconditions,theBoyko-Kruzhilinequation given above, Eq. (D.14a) et seq., becomes valid.
Again, a conservative and simple procedure for estimating a condensing coefficient for vertical tubes is
to calculate the. coefficient by all threeequations,
(D.14), (D.15), and (D.161,andselectthe highest
coefficient.
(D.14e)
0
The correlationsof Kern and Chaddock are valid at
low vapor flow rates, where gravity dominates the
flow pattern,andareinvalidat high vapor flow rates,
. wherevaporsheardominates.TheBoyko-Kruzhilin
correlation operates in exactly the opposite fashion.
Comparisonof the fundamentalbases for each equation indicates that the correlation
which is valid under
a given set of conditions gives a higher heat transfer
coefficient than the invalid correlation. Therefore, to
determine which type of correlation is applicable in
a given situation, one may calculate the coefficient
by each method and select the higher.value. In the
transition region where the correlations
cross, the actual coefficients are found to be greater than those
predicted by either type of correlation. The values of
6, calculated by theseequationsaremeanvaluesfor
the entire tube. Calculation of the local values is beyond the scope of this standard;Ref. I191 may be
consulted as a typical example.
D.3.3.3 Inclined Tubes.Very fewdatahavebeen
published on condensation in downward flow inside
inclined tubes, though proprietary data and correlations exist. It is reported that the condensing coefficient increases significantly (compared to a vertical
tube) in a tube which is inclined from 1 deg. to 20
deg. from the vertical. As the inclination moves toward the horizontal, the coefficient changes toward
that for a horizontal tube.
Nilsson (Ref. [21]) has shown that a very slight (1
to 2 deg.) upward inclination in a horizontal tube can
cause substantial reduction in the condensation heat
transfer coefficient, presumably because
of excessive
pooling of the liquid in the lower end of the tube.
D.3.3.2 Vertical Tubes. Nusselt (Ref. [I611 also obtained an equation for Condensation under laminar
condensate film conditions in vertical tubes (correspondinggenerally to low condensingrates).This
equation is
I-
D.3,4 Mean Temperature Difference for Saturated
PureComponentCondensation.
Themean temperature difference for condensation of a saturated
pure vapor, assuming a constant overall heat transfer
1113
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-ASME P T C * 3 0 91
'
O759670 0083304 2
--``-`-`,,`,,`,`,,`---
ASME PTC 30-1 991
AIR COOLED HEAT EXCHANGERS
6
9
O
II
a
Q
I
t
t-
8
72
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9:
O
A S I E PTC*30 71
O757670 0083305 4
ASME PTC 30-1991
AIR COOLED HEAT EXCHANGERS
O
1 .o0
0.95
0.90
0.85
0.80
ß
0.75
0.70
O. 65
0.60.
0
0.5
1.5
1.0
*",
c
.
radians
,t -G
\
is
sure existing in the vapor space. In this case, it has
been shown that the above-referenced equationsfor
condensing a saturated vapor adequately predict the
heat transfer rate on the vapor side, if the saturation
temperature of the vapor is used as the process fluid
temperature in Eq. (D.17). It is necessary to include
in the heat load the sensible heat of cooling the vapor,even though its temperature is ignored in calculating the EMTD.
If the sutface is above the saturation temperature,
the vapor will cool sensibly by the usual single phase
convectiveprocess until it reaches a temperature
such that the wall does become wet. In principle, it
is only necessary to follow the cooling of the vapor
and the wall temperature until the wall reaches saturation - temperature and then follow the procedure
given in the previous paragraph.
However, such local vaporcooling calculations are
tedious because the vaportemperaturechanges
alongeachtubeand
theairtemperature changes
across each row of tubes as well as along each tube.
(D.17)
where TSatis thesaturationtemperature of thecondensing vapor.
The EMTD under these conditions is independent
of flow arrangement. It should be noted that in fact
the local condensing coefficients do vary with local
quality, but the effect on the overall coefficient
is
ordinarily small. Consideration of these effects is in
any case beyond the scope of this-document.
D.3.5 SuperheatedVapors.
A superheatedvapor
will condense directly from the superheated stateon
a surface that is even slightly (perhaps 0.01"F)below
the saturation temperature of the vapor at the pres73
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3.0
ß AS A FUNCTION FOR I),,, FOR THE CHADDOCK METHOD
coefficient, and constant saturation temperature,
given by:
EMTD = LMTD =
2.5
Not for Resale
--``-`-`,,`,,`,`,,`---
FIG. D.4
2.0
ASME PTC*130
91 .
I0 7 5 9 6 7 0 008330b b E !
ASME PTC 30-1991
--``-`-`,,`,,`,`,,`---
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0757670 0083307 8
AIR COOLED HEAT,EXCHANGERS
These calculationsrequirevapor-liquid equilibrium
and enthalpy calculations that are usually computerbased and supplied by the customer. Before any conclusions can be drawn about the performanceof the
condenser, mutual agreement must be reached between customer and vendor on the validity of these
calculations.
(b) Sensibleheattransfereffects(¡.e./
cooling of
the vapor-gas mixture) are always present in multicomponent condensation in both the vapor-gas and
liquid phases. The cooling of the vapor-gas mixture
tends to be an important and often controlling part
of the heat transfer process.
(c) Mass transfer effects are always presentin multicomponent condensation. These processes areonly
poorlyunderstoodandmust be treated in a fairly
arbitrary manner.The specific problem of a single
condensable vapor with a noncondensable gas can
be handled with some rigor as shown in Ref. [231.
(d) Physical properties changein both phases, both
as a result of changing compositions and changing
temperatures.
Usually, careful analysis of multicomponent condensationproblems (which may includenoncondensable gases) requires zone-by-zone analysis on a
computer. However, if the condensing temperature
range is relatively small compared to the mean temperature difference, orif only a small amount of condensate is formed,approximatecalculations
. of
sufficient accuracy may be possible (Ref. [24]).
In thesecases, the heattransferprocesson
the
tube side may be considered to consist of tw6 resistances in series:
( I ) Sensible heat transfer from the vapor-gas mixture to the condensate interface,with a typicalvaporphase heat transfercoefficient h,, calculated from the
correlations in para. D.2, and,
(2) Convection of the sensible heat from (1) above
and the latent heat released by condensation at the
interface through the condensate layer, with a condensing heat transfer coefficienthi,=.
A combined coefficient forthese two processes on
the condensing side, h, maybecalculatedby
Eq.
(D.18a)
Reference i221 shows that the heat transfefflux for
cooling a superheated vapor must be higher than the
condensing flux if the wall is to remain dry. Therefore,
if it is assumed that the vapor is desuperheating in
the wet wall regime from the start (using the simple
procedure given in the first paragraph), the area calculated to be required will either be correct (if the
wall is wet even at the vapor entrance)or conservative
(if some portion of the wall is in fact dry). The term
correct means that the calculated area is as close to
that actually required as the validity of the correlations permits; conservative means that the calculated
area is larger than would be obtained by a detailed
local
calculation.
e
D.3.6 Subcooling of Condensate, When subcooled
condensate is required, it is customary to design the
condenser so that the bottom row or rows of tubes,
disposed in one or more passes, run full of condensate. The liquid phase heat transfercoefficient canbe
calculated using the correlations given in para.D.2
and the heat transfer rateby using a corrected
LMTD,
the correction factors being
given in para. 5.5 for the
appropriate pass arrangement.
The averageair temperature leaving
the subcooling
section can be calculated by a heat balance. Without
going to a zone-by-zone analysis (which requires a
computer program for all practical purposes), it is
necessary to assume that the average air temperature
off of the subcooling rowsis equivalent to a uniform
inlet air temperature to the condensing rows. This is
of course not the case,and it is usually somewhat
nonconservative to assume so. In analyzing the performance of an existing unit, this factor can be taken
.into account qualitatively without a great deal of
computation.
D.4 MULTICOMPONENT CONDENSATION,
INCLUDING NONCONDENSABLE GASES
@
There are several special problems associated
with
the condensation of a multicomponent mixturenora
vapor containing anoncondensable gas. Amongthem
are the following:
(a) It is necessary for accuratedesign to have a
condensingcurve for the mixture; acondensing
curve gives the temperature of the condensing mixture and the fraction of the flow that has been condensed as a function of the amount of heat removed.
h, =
-+-
(D.18a)
1
h,,h,
where
Z=
75
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z
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QS"
Q, + QL+
(D.18b)
Qd
--``-`-`,,`,,`,`,,`---
ASME PTC 30-1991
0759670 0083308 T I
ASME P T C 8 3 0 91
AIR COOLED HEAT EXCHANGERS
ASME PTC 30-1991
(c) Reduction in number of tubes in successive
passes in condensing(andsometimessubcooling)
service in order to maintain high vapor velocity and
condensing coefficients. Note however that uniform
distribution of the two phases among the tubes in
later passescan not be expected, and this can lead
to excessive subcooling in sometubesand incomplete condensation in others.
(d) Multiple servicesmay be handled in a.single
unit, usually with the sections in parallel on the air
flow (side-by-side in the frame). Different tube sizes
and number of rows may be used in each section.
(e) A single row of tubes may be split between two
passes in order to obtain the same number of tubes
in eachpass,e.g., two passes in five rows of tubes.
(0 A row oftubes may contain asingle tube (or at
most a few tubes) servingas a vent condenseroff of
an air removal point and having a differentinlet and
outlet header connection.
Thermal analysis of types a, b, and c can be carried
out by a procedure similar
to that suggested for subcooling sections above, and with the same caution
upon assuming the air
inlet temperature to the upper
rows of tubes to be uniform.
Type d can be analyzed straightforwardly foreach
section if the air flow and exit air temperature for
each section are measured.
Type e can .be analyzedreasonablycloselyby
straightforward methods, using the actual numberof
tubes in each pass for tube-side calculations and ignoring the usually slight imbalance in the air temperature profile caused by the split pass or passes.
Type f poses no serious problems on the air side
since only a few tubes are involved.The analysis-inside the tube can be carried out by the methods of
para, D.4 or Ref. [231.
Q, is the heat duty required to cool the vapor-gas
mixture:
QLis the heat duty required for condensation:
Q, = X W p , c o n d
(D.
18d)
Q,, is the heat duty required for cooling the condensate:
-
wp," an'cl Wp,,are the average weight flow rates of
vapor and condensate in the condensingprocess, and
Wp,condis the amount of vapor actually condensed.
D.5 UNUSUAL PASSARRANGEMENTS
For. avariety of reasons,unusualpassarrangements of various kinds are often used in air cooled
exchangers, The following examples may be cited:
(a) Reduction in number of tubes in successive
passes,used in cooling viscous liquids in order to
increase thevelocity and maintainturbulent flow
conditions.
(b) Using enhancement devices in one or more of
the last passes for the same purpose.
76
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ASME PTC 30-1991
AIR COOLED HEAT EXCHANGERS
APPENDIX E
- FOULING
E,1 Theexchangerdesignerincorporates
a heat
transfer fouling resistance to account for the accumulations of layers of resistive material on the heat
transfer surfacesas the exchanger operates. Thefouling resistance is also known as fouling factor, dirt factor, and dirt film. The fouling resistance occurs on
both the air-side and the process-side heat transfer
surfaces. Unfortunately,. the existing technologydoes
not provide a dependable analytical method for accurate prediction of fouling. The purchaser normally
depends on experience in similar services to select
and specify the design fouling resistances.
should preferablybe performed in the clean condition
on bóth air-side and tube-sideto minimize the effects
of fouling since fouling cánnot be reliably predicted.
The fouling resistances used to interpret the test results shall be agreed upon by the parties to the test
prior to the start of the test, see para. 3.2(j).
E.3 the influence of foulingon the overall heat transfer coefficientwill vary accordingto the relative-magnitudes of the fouling resistances and the clean heat
transferresistances. For example, a closed-circuit
treated'water coolermight have a low tube-side fouling resistance of 0.0005 hr.ft*-"F/Btu referencedto the
inside surface. Thismight be approximately5 percent
of the total heat transfer resistance. In comparison,
this resistancefor aheavy oil cooler might be 0.003
hr.ft2-"F/Btuwhich might be over 20 percent of the
total heat transfer resistance, making a clean condition for testing relatively more important.
E,2 Fouling presentduringthe test affects the air-side
and process-side heat transfer coefficients and flow
pressure drops. Fouling of the air-side surface may
occur from the depositionof air-borne materials such
as dust, organic material, seeds, and insects, or from
corrosion. It is impossible to accurately predict the
effect of such deposits and they must be removed
prior to testing. Fouling of the inside surface of the
tubes is dependent upon the fouling and corrosion
characteristics of the fluidin the tubes.Testing
E.4 For additionai information on fouling the reader
may refer to Ref. [25].
77
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ASME PTC 30-1991
AIR COOLED HEAT EXCHANGERS
APPENDIX F
O
0
F.1 Advkse wind conditions, faulty design, or poor
orientation of the ACHE with respect to adjacent
structures may cause hot air to recirculate into the
unit. The resultantelevation of enteringairtemperature above ambient will reduce the capacity of the
ACHE. Simitayly, contämination of the entering air by
hot air from extraneous heat sources, such
as heaters,
boilers, or heat exchangers, will have a detrimental
effect on capacity.
be basically the same as for a test conducted when
there is no air recirculation or contamination. However, entering air temperatures may be far from uniform. Temperature variations at
a given measurement
station and/or variationsfrom station to station, coupled with variations in air velocity, may require an
abnormaliy large number of measurement stations,
and may necessitate
coincident measurement of temperature and air flow at each station.
F.2 Since the performance evaluation procedures described by this Code are based
on entering rather than
ambient air, the-recirculation and/or contamination
described abovewill not necessarily havea significant
effect op the performance capabirity of the ACHE. The
results of a test conducted while the entering air temperature is well above ambient, but uniform, should
F.3 A detailed survey should be made just prior to
the test, and agreement reachedby theparties to the
test on the number andlocation of measurements to
be taken to ensure the desired level of accuracy.
F.4 For more information on this subject the reader
is referred to Refs. [27] through 1361.
--``-`-`,,`,,`,`,,`---
(I,
- RECIRCULATION OF AIR
V
O
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ASME PTC 30-1991
AIR COOLED HEAT EXCHANGERS
APPENDIX G - REFERENCES
[I 1 FieldTesting
of Air-CooledHeatExchangers,
Chemical Engineering Progress, July 1960.
[I41Kern, D. Q., Process Heat Transfer, McGraw-Hill
Book Company, New York (1950).
[2]Flow of Fluids Through Valves, Fittìngs, and Pipe
- Crane Co., Technical Paper No. 410, 1978.
[I 51 Martinelli, R. C., and Nelson, D. B., Trans. ASME
70,695, (1948).
[3]Fundamentals of Pipe Flow, R. P. Benedict, Wiley,
-1980.
VDI 60, 541,
[I61 Nusselt,W.,Zeits.
Also cited in Refs. 161 and [91.
[4]Sieder, E. N., andTate,G.
28, 1429 (1936).
[I 71 Chaddock, J. B., Refrig.Eng.65,No.
E., Ind. Eng.Chem.,
N., Int. J. Heat
[I81 Boyko, L. D.,andKruzhilin,G.
Mass Trfr. 70, 361 (1967).
[61Ward, D.J., and Young, E. H., Heat Transfer and
Pressure Drop of Air in Forced Convection Across Triangular Pitch Banks of Finned Tubes, Chemical Engineering Symposium Series No. 29, Vol. 55, 1959.
r201 Colburn, A. P., Trans. AlChE 30, 170
[7]Gardner, K. A., Efficiency of ExtendedSurface,
ASME Transactions Paper 1945,Vol. 67.
1221Bell, K. J., Chem. Eng. Prog. 68, No. 7,81
Trans. ASME 66, 671
[I91 Travis, D. P., Baron, A. B., andRohsenow,W.
M., MIT Rept. No. DSR 72591 -74
(1971 1.
[21]Nilsson, S . N.,Paper 2.32, Proc. Xlll Int. Cong.
Refrig., Washington, DC (1971),
[231 Colburn, A. P., andHougen,
Chem. 26, 1186, (1934).
(1944).
[9]Blasius, H., Forschg. Arb. h g -Wes. No. 131,Berlin (1913).Cited in Schlicting, H., BoundaryLayer
Theory, 7th ed., McGraw-Hill Book Co., New York
(I979).
(1972).
O. A., Ind. Eng.
r241 Bell, K.J., and Chaly, M.A., AlChE Symp. Series
69, NO. 131, 72-79 (1972).
[25]Kakac, S., Bergles, A.E., and Mayinger, G., Heat
Exchangers: Thermal-Hydraulic Fundamentals and Design, McGraw-Hill, and Hemisphere Publishing Corp.
(I 9811.
[I O] Shah, R. K., and London, A. L., Advances in Heat
Transfer, Supplement1: Laminar Flow Forced Convection in Ducts, Academic Press, New York (1978).
i261 TubularExchangerManufacturersAssociation,
Standards of TEMA, latest edition.
[Il]Hausen,H., VDlZ Beih. Verfahrenstech. 4. 91
(1943).Cited in Ref. [12].
L271 Gunter, A. Y., and Shipes, K. V., “Hot Air Recirculation .by Air Coolers,”AlChE
TwelfthNational
Heat Transfer Conference, AIChE-ASME, Tulsa,Oklahoma, August 15-1 8, 1971.
1121 Jakob, M., Heat Transfer, J. W: Wiley and Sons,
New York, Vol. 1 (1949).
[I31 Petukhov, B. S., and Popov, V. N., Teplofiz. Vysok. Temperature 7, No. 1 (1963).Also discussed by
B. S, Petukhov in Advances In Heat Transfer, Vol. 6,
Hartnett, J. P., and Irvine, T. F., Jr. Eds., Academic
Press, New York (1970).
1281 Collins, G. F., andMathews, R. T., “Climatic
Considerations in Design of Air Cooled HeatExchangers,“Paper 59-A-255,December 4, 1959,
Annual
Meeting ASME.
81
Copyright ASME International
Provided by IHS under license with ASME
No reproduction or networking permitted without license from IHS
(1934).
Not for Resale
--``-`-`,,`,,`,`,,`---
F.,
4, 36
(1957).
[5]Briggs, D. E., and Young, E. H., Convection Heat
Transfer and Pressure Drop of Air Flowing Across Triangular Pitch Banks of Finned Tubes, AIChE, August
1962.
[8]Moody, L.
O
569(I916).
ASME P T C U 3 0 7.1 m O757670 8083332
I m
i
AIR COOLED HEAT EXCHANGERS
ASME PTC 30-1991
[34] Haldridge, E. S., and Reed, B. H., ”Pressure Distribution on Buildings,” Department of Army, Contract No. DA-18-064 CML77,August1956,Texas
Engineering Experiment Station, Texas A & M.
1291CoolingTower InstituteTechnical Subcommittee
No, 2: “Recirculation,” C T I Bulletin PFM-110, 1958.
Also PFM-11OA, Appendix to PFM-11O.
[30] Schmidt, W., “Calculations of Distribution of
Smoke
and
Waste
Gases
in the Atmosphere,”
Gesundheits Ing. Vol 49, 1926, pp. 425-426.
1351 Haldridge, E. S., and Reed, B. H., “Pressure Distribution on Buildings-ReportNo. 2,” Department of
Army, Contract No. DA-18-064 CML77,
August
1956,
Texas
Engineering
Experiment
Station,
Texas A & M.
-
[31] Sutton, O. G., “A Theory of Eddy Diffusion in
the Atmosphere,“ Proc. Roy. Society (London) Ser. A
Vol. 135, 1932, PP. 143-1 65.
[36] Kosten, C. J., Morgan, J. I., Burns, J. M., and
Curlett, P. L., “OperatingExperienceandPerformanceTesting
of theWorlds
Largest Air Cooled
Condenser,” April 27-29,1981,AmericanPower
Conference, Chicago, Illinois.
1321 Bailey,A., and Vincent,N.D. G., “Wind Pressure
on Building Including Effects on Adjacent Building,”
Journal Institution of Civil Engineer, March 1943,
PP. 243-275.
--``-`-`,,`,,`,`,,`---
[33] Dryden, H. L., and Hill, C. C., “Wind Pressures
on Structures,” Scientific Papers of Bureau of Standards, Vol. 20, 1926, p. 697.
82
Copyright ASME International
Provided by IHS under license with ASME
No reproduction or networking permitted without license from IHS
Not for Resale
COMPLETE LlSTlNC OF ASME PERFORMANCE TEST CODES
PTC 3.1
PTC 3.2
PTC 3,3
PTC 4.1
- General Instructions ....................,...............................I986
- Definitions and Values ..........,......................................1980
(R1985)
- Diesel and Burner Fuels ......,.,......,...............................I958
(RI985)
- Solid Fuels ,.......,..,...........,..,......,...,........,...............I954
(R1 984)
- Gaseous Fuels ..,.. ..,......,.,......,.,...,,.........,...,...........,1969
(R1 985)
- Steam-Generating Units (With 1968 and
1969 Addenda) .. .............. .....,................................I964
.,
(R1 985)
PTC 4.la
PTC 4.1b
PTC 4.2
PTC 4.3
PTC 4.4
PTC 5
PTC 6
Diagram for Testing of a Steam Generator,
Fig. 1 (Pad of 100)
Heat Balance of a Steam Generator,
Fig. 2 (Pad of 100)
ASME Test Form for Abbreviated EfficiencyTest
Summary Sheet (Pad of 100)
,
, ,
- ASME Test for Abbreviated EfficiencyTest Calculation Sheet (Pad of 100)
Coal Pulverizers , ,
, ,
,,
,
-
-
......... .... . ......,........,.......I964
........................ ..............1964
. . ........ . ....... ...... .......,......,......,...I969
(R1 985)
- Air Heaters ...... ... ...
............ ......... ..........................I968
(RI 985)
- Gas Turbine HeatRecovery Steam Generators........................I981
(RI 987)
- ReciprocatingSteam Engines ..................,.......................I949
- Steam Turbines .... ....................,......,............,............1976
(R1 982)
PTC 6A
PTC 6
Report
PTC 6 s
Report
PTC 6.1
PTC 7
PTC 7.1
PTC 8.2
- Appendix Ato Test Code for Steam Turbines
(With 1958 Addenda) ...............,,......,.......................1982
- Guidance for Evaluation of Measurement Uncertainty
in Performance Tests of Steam Turbines .........................,..I985
- Procedures for Routine Performance Tests
of Steam Turbines ...............,....................,..............I988
- Interim Test Code for an Alternative Procedure
for Testing Steam Turbines ...........,......... ...
,.............,...I984
PTC 6 on Steam Turbines- Interpretations 1977-1983
- Reciprocating Steam-Driven Displacement Pumps...............,....1949
(R1 969)
- Displacement Pumps ............................,...............,......I962
(R1969)
- Centrifugal Pumps .. ..........,......,.......,.................,......,1990
Copyright ASME International
Provided by IHS under license with ASME
No reproduction or networking permitted without license from IHS
Not for Resale
--``-`-`,,`,,`,`,,`---
PTC 1
PTC 2
ASME P T C * 3 0 71 W 0757670 QQB3314 5
PTC 9
.
Displacement Compressors. Vacuum Pumps and
......................................... 1970
(R1
985)
- CompressorsandExhausters .......................................... 1965
(RI
986)
- Fans ..................................................................... 1984
- Closed Feedwater Heaters .............................................. 1978
(RI 987)
- Steam-Condensing Apparatus .......................................... 1983
- Deaerators .............................................................. 1977
(R1984)
- EvaporatingApparatus ................................................. 1970
(RI985)
- Gas Producers and Continuous Gas Generators ...................... 1958
(RI
985)
- Reciprocating Internal-combustion Engines ........................... 1973
(R1985)
- HydraulicPrimeMovers ................................................ 1949
- Pumping Mode of Pump/Turbines ..................................... 1978
(R1
984)
- MeasurementUncertainty .............................................
1985
- Pressure Measurement ................................................. 1987
- TemperatureMeasurement ............................................. 1974
Blowers(With 1972 Errata)
PTC IO
PTC 11
PTC 12.1
PTC 12.2
PTC 12.3
PTC 14
PTC 16
PTC 17
PTC 18
PTC 18.1
PTC 19.1
PTC 19.2
PTC 19.3
PTC 19.5.1
PTC 19.6
PTC 19.7
PT% 19 8
- Application, Part II of Fluid Meters: Interim Supplement
on Instruments and Apparatus ......................................
- WeighingScales ........................................................
- Electrical Measurements in Power Circuits ............................
- Measurement of Shaft Power ...........................................
- Measurement of Indicated Horsepower ...............................
PTC 19.1O
PTC 19.11
- Flue and Exhaust Gas Analyses ........................................
- Water and Steam in the Power Cycle (Purity and Quality,
PTC 19.5
Lead Detection and Measurement)
PTC 19.12
PTC 19.1 3
PTC 19.14
PTC 19.16
PTC 19.1 7
PTC 19.22
PTC 19.23
PTC 20.1
.................................
- Measurement of Time ..................................................
- Measurement of Rotary Speed .........................................
- LinearMeasurements ..................................................
- Density Determinations of Solids and Liquids ........................
- Determination of the Viscosity of Liquids .............................
- Digital Systems Techniques ............................................
- Guidance Manual for Model Testing
..................................
- Speed and Load Governing Systems for Steam
Turbine-Generator Units
..............................................
'
PTC 20.2
- Overspeed Trip Systems for Steam TurbineGenerator
Units
PTC 20.3
.................................................................
- Pressure Control Systems Used on Steam
Turbine-Generator Units
.............................................
--``-`-`,,`,,`,`,,`---
Copyright ASME International
Provided by IHS under license with ASME
No reproduction or networking permitted without license from IHS
Not for Resale
(R1
986)
1972
1964
1955
1980
1970
(R1
985)
1981
1970
1958
1961
1958
1965
1965
1986
1980
(RI
985)
1977
(R1988)
1965
(RI
986)
1970
(R1979)
.
.Dust Separating Apparatus .............................................
PTC 21
PTC 22
PTC 23
PTC 23.1
PTC24
- Gas Turbine Powér Plants ..............................................
- Atmospheric Water Cooling Equipment ...............................
- Spray Cooling Systems .................................................
PTC 25.3
PTC 26
- Speed-Governing Systems for Internal Combustion
- .Ejectors .................................................................
- Safety and Relief Valves ................................................
€ngine-Generator Units
..............................................
1941
1985
1986
1983
1976
(R1982)
1988
1962
PTC 28
- Determining the Properties of Fine Particulate Matter ................1965
PTC 29
- Speed Governing Systems for Hydraulic
PTC 30
PTC 31
.............................................
- Air Cooled Heat. Exchangers ...........................................
- Ion Exchange Equipment ...............................................
PTC 32.1
- Nuclear Steam Supply Systems ........................................
PTC 32.2
- Methods of Measuring the Performance of Nuclear
Turbine-Generator Units
(R1985)
1965
(RI 985)
1991
1973
(R1 985)
1969
(R1985)
............................... 1979
(R1986)
...................................................... 1978
Reactor Fuel in Light Water Reactors
PTC 33
PTC 33a
- Large Incinerators
- Appendix to PTC 33-1978 - ASME Form for
Abbreviated Incinerator Efficiency Test
(Form PTC 33a-1980)
...............................................
PTC 36
PTC 38
- Measurement of Industrial Sound .....................................
- Determiningthe Concentration of Particulate
PTC 42
The Philosophy of Power Test Codes and Their Development
--``-`-`,,`,,`,`,,`---
Copyright ASME International
Provided by IHS under license with ASME
No reproduction or networking permitted without license from IHS
1980
(R1 987)
1985
.........1.................................... 1980
(RI985)
- Condensate Removal Devices for Steam Systems .................... 1980
(RI 985)
- Wind Turbines .......................................................... 1988
Matter in a Gas Stream
PTC 39.1
(R1 985)
Not for Resale
¡ASME P T C r 3 0 9L E 0759b70 0 0 8 3 3 L b 9
~
A complete list of all Performance Test Codes appsars
at the end of this book.
While providing
for exhaustive
tests, these Codes are so d r a w n
thatselectedpartsmay
for tests of
be used
limited scope,
This document is printed
o n 50% recycled paper.
--``-`-`,,`,,`,`,,`---
50% RECOVERED PAPER MATERIAL
means paper waste generated after the
completion of the papermaking
process, such as postconsumer
materials, text books, envelopes,
bindery waste, printing waste, cutting
and converting waste, butt rolls,
obsolete inventories, and rejected
unused stock.
C00057
ISBN #O-7918-2073-4
Copyright ASME International
Provided by IHS under license with ASME
No reproduction or networking permitted without license from IHS
Not for Resale