Last Rev.: 12 JUN 08
REFRIGERATION CYCLE ANALYSIS : MIME 3470
Page 1
Grading Sheet
~~~~~~~~~~~~~~
MIME 3470—Thermal Science Laboratory
~~~~~~~~~~~~~~
Laboratory №. 17
REFRIGERATION CYCLE ANALYSIS
Students’ Names / Section №
POINTS
PRESENTATION—Applicable to Both MS Word and Mathcad Sections
5
5
5
GENERAL APPEARANCE
ORGANIZATION
ENGLISH / GRAMMAR
ORDERED DATA, CALCULATIONS & RESULTS
PLOT ACTUAL CYCLE (W/ BLOCK ARROWS)
10
10
10
CALCULATE COPOA
10
TABLE OF PROPERTIES FOR THE 8 STATES
PLOT IDEAL CYCLE (W/ BLOCK ARROWS) USING PRESSURES 3 & 8
ideal
& COPOA
act
TECHNICAL WRITTEN CONTENT
DISCUSSION—GENERAL DISCUSSION OF CALCULATIONS
EXPLAIN IN TERMS OF 1ST & 2ND LAWS THE DISCREPENCIES
BETWEEN THE TWO PLOTS ABOVE
ARE THE DISCREPENCIES IN THE PROPER DIRECTION(S)?
SHOULD THERE BE DIFFERENCES BETWEEN THE ACTUAL &
IDEAL CYCLES?
CONCLUSIONS
ORIGINAL DATASHEET
TOTAL
COMMENTS
d
GRADER—
5
10
10
10
5
5
100
SCORE
TOTAL
Last Rev.: 12 JUN 08
REFRIGERATION CYCLE ANALYSIS : MIME 3470
 R h1  h4 
Q evap  m
MIME 3470—Thermal Science Laboratory
~~~~~~~~~~~~~~
Laboratory №. 17
m R = mass flow of refrigerant through the system.
Therefore, from Equation 1, the ideal COP is
Q evap h1  h4
.
(5)
COPOAideal 

W comp h2  h1
~~~~~~~~~~~~~~
NAME
NAME
NAME
TIME, DATE
Condenser



 Compressor


Valve
Constant p

Wcomp


Evaporator
Q evap
s


 

 air c p Tin
Q evap  m
 Toutevap
evap
air
evap
 air
where, m
=
evap
(1)




 Compressor




Wcomp
p1


s
Evaporator
Q evap
Figure 2—Schematic and T-s diagram for a vapor-compression
refrigeration cycle including irreversibilities in all components
The refrigeration cycle for an actual cycle is presented in Figure 2.
This cycle varies from the ideal in that the compression process is nonisentropic (States 1 to 2) and there are pressure losses across both the
evaporator (States 7 to 8) and the condenser (States 3 to 4). The cooling
capacity, Q evap , and the heat load from the condenser, Q cond , are
 R h8  h7 
Q evap  m
(6)
and
Q cond  m R h3  h4 
(7)
and
 air c p Tin
Q cond  m
 Toutcond
air
cond


(8)
air temperatures in and out of the condenser.
Equation 3 would be valid for an actual cycle only if the
compression and combination compressor-motor efficiencies were
both unity. The compression efficiency,  comp , and the compressor-
 comp 
and
 c -m 
h2 s  h1
h2  h1
w R h2 s  h 1
W
(2)
mass flow of air through the evaporator
c pair = specific heat of air
Tinevap = temperature of air entering the evaporator
Toutevap = temperature of air leaving the evaporator
The refrigeration cycle in Figure 1 is an ideal cycle. It is ideal
because the compression process is isentropic (States 1 to 2) and
there are no pressure losses across either the evaporator (States 4
to 1) or the condenser (States 2 to 3). The power to the compressor
and the cooling capacity for the ideal refrigeration cycle are
 R h2  h1 
(3)
W comp  m
(9)
(10)
comp
Therefore, the cycle overall COP for actual cycle is
h h
COPOA  8 7
h2  h1
act
electric power to the compressor motor.
From the First Law, the cooling capacity is

p8


motor efficiency,  c-m , are defined by
ANALYSIS—The performance of a refrigeration cycle is given in
terms of the Coefficient of Performance or COP and the cooling
capacity Q evap . The overall COP for the cycle is


COPOA  Q
evap Wcomp




Figure 1—Schematic and T-s process diagram of an
ideal vapor-compression refrigeration cycle
where, Wcomp =
Condenser
Equation 8 is obtained from an energy balance across the air
side of the condenser. The temperatures Tincond and Toutcond are the

Expansion
(Throttling)
Constanth


Q cond


T
OBJECTIVE—of this exercise is to determine the various
coefficients of performance, COP. Specifically, these are the ideal
and actual cycle COPs using the attached thermodynamic diagram
for Refrigerant-12 (R12).
INTRODUCTION—A refrigeration cycle is a cycle which
transfers heat from a low temperature sink to a high temperature
sink by the application of energy from a third source. A
refrigeration cycle differs from what is commonly called a heat
pump in that the desired output is the heat transfer from the cold
sink rather than the heat transfer to the hot sink.
The most common type of refrigeration cycle is the mechanical
vapor compression cycle. This cycle is essentially a Rankine
Cycle run backwards. A schematic and a T-s diagram of the cycle
appears in Figure 1. The cycle is referred to as a mechanical
compression because the compression process (States 1 to 2) is
accomplished by a mechanical compressor that is driven by an
external power source. This source is usually an electric motor.
Constant p
Q cond
p
 2
~~~~~~~~~~~~~~
T
(4)
where,
REFRIGERATION CYCLE ANALYSIS
LAB PARTNERS: NAME
NAME
NAME
SECTION
№
EXPERIMENT TIME/DATE:
Page 2
(11)
PROCEDURE—Turn on and study the cycle and the components of
the refrigeration unit shown in Figure 3. Trace the R12 flow path and
identify the compressor, evaporator, condenser, and expansion valve
inlets and outlets. Make sure that the flow path is correct by opening
and closing the proper valves. For the unit to act on a refrigeration
cycle, the flow from the evaporator must go to the top of the
compressor.
After the unit has stabilized, take temperature and pressure data
for flows into and out of the
a. Compressor (States 1 and 2)
b. Condenser (States 3 and 4)
c. Expansion valve (States 5 and 6)
d. Evaporator (States 7 and 8).
Last Rev.: 12 JUN 08
REFRIGERATION CYCLE ANALYSIS : MIME 3470
Page 3
For the Report
NOTE: This experiment is to be done in English units only.
This is because the only pressure-enthalpy diagram for Freon-12
we have access to is in English units.
1. Make a table (supplied below) of state properties (p, T, v, h,
and s) for the eight states of the cycle.
2. On the supplied p-h chart, plot the ideal cycle for the appropriate conditions of our experimental data. The student is to
use Pressures 3 and 8 to determine the ideal cycle. Be sure to
indicate with block arrows across the lines the occurrences of
Q cond m , Q evap m , and W comp m .
3. Redo Item 2 using the actual cycle data points. This plot
should appear on the same sheet as that of Item 2.
4. Calculate COPOA and COPOA
ideal
Figure 3—Refrigeration cycle experimental setup
act
5. Explain in terms of the First and Second Laws
Thermodynamics, the nature of the discrepancies between
cycle paths in Items 2 and 3. Are the discrepancies in
proper direction(s)? Should there be differences between
actual and ideal cycles?
of
the
the
the
ORDERED DATA, CALCULATIONS, and RESULTS REMEMBER: DO THIS ONE IN ENGLISH UNITS ONLY
Requirement 1: Make a table of state properties (p, T, v, h, and s) for the eight states of the cycle.








State
Compressor Compressor Condenser Condenser Expansion Expansion Evaporator Evaporator
Data
In
Out
In
Out
Valve In
Valve Out
In
Out
p(psi)
gage
p(psi)
absolute
(+14.7psi)
T(F)
v(ft3/lbm)
h(Btu/lbm)
s(Btu/lbmR)
Requirement 4.Calculate COPOA
and COPOA .
ideal
act
The student may want to use the Mathcad object (below) for this. Otherwise, feel free to delete the object.
MATHCAD OBJECT--DOUBLE CKICK TO OPEN
YOU MAY NOT CHOOSE TO USE MATHCAD ON THIS LAB.
THE OBJECT IS PRESENTED IF YOU WANT IT.
OTHERWISE DELETE THE OBJECT.

Last Rev.: 12 JUN 08
REFRIGERATION CYCLE ANALYSIS : MIME 3470
Page 4
Requirements 2 & 3. On the supplied p-h chart, plot the ideal cycle for the appropriate conditions of our experimental data. The student is to
use Pressures 3 and 8 to determine the ideal cycle. Be sure to indicate with block arrows across the lines the occurrences of Q cond m ,
Q evap m , and W comp m .
Redo Item 2 using the actual cycle data points. This plot should appear on the same sheet as that of Item 2.
Q cond
m














IDEAL CYCLE
ACTUAL CYCLE
Last Rev.: 12 JUN 08
REFRIGERATION CYCLE ANALYSIS : MIME 3470
DISCUSSION OF RESULTS
Explain in terms of 1st and 2nd Laws the discrepencies between
the two plots.
Answer:
Are the discrepencies in the proper directions?
Answer:
Should there be differences between the actual and ideal
cycles?
Answer:
CONCLUSIONS
Page 5
Last Rev.: 12 JUN 08
REFRIGERATION CYCLE ANALYSIS : MIME 3470
Page 6
APPENDICES
APPENDIX A—DATA SHEET FOR REFRIGERATION CYCLE ANALYSIS
NOTE:
1. THE CONDENSOR IS ON THE HIGH PRESSURE SIDE
Q cond


Condenser
WHILE THE EVAPORATOR IS ON THE LOW PRESSURE SIDE
2. ALL PRESSURE DATA ARE GAGE PRESSURES; HOWEVER,
THE PROPERTY TABLES USE ABSOLUTE PRESSURE—BE SURE
TO CONVERT TO ABSOLUTE BEFORE LOOKING UP PROPERTIES.

___________________________
Lab Partners:
___________________________ ___________________________
p(psi)
T(F)
___________________________
___________________________
___________________________
___________________________

Compressor
In
d
d

Compressor
Out

Condenser
In


 Compressor




Wcomp
Time/Date:
State
Data



Condenser
Out

Expansion
Valve In

Expansion
Valve Out


Evaporator
Q evap

Evaporator
In

Evaporator
Out
Last Rev.: 12 JUN 08
REFRIGERATION CYCLE ANALYSIS : MIME 3470
APPENDIX B—R-12 (CCl2F2) THERMODYNAMIC PROPERTIES
Saturated
Superheated
v(ft3/lbm), u(Btu/lbm), h(Btu/lbm), s(Btu/lbm°R)
Page 7
Last Rev.: 12 JUN 08
REFRIGERATION CYCLE ANALYSIS : MIME 3470
APPENDIX C—BIOGRAPHIC SKETCHES
The Father of Cool
Willis Haviland Carrier—The History of Air Conditioning
By Mary Bellis
“I fish only for edible fish, and hunt only for edible game even in
the laboratory.” — Willis Haviland Carrier on being practical.
In
1902, only one year after Willis
Haviland Carrier graduated from Cornell
University with a Masters in Engineering, the first air (temperature and humidity) conditioning was in operation,
making one Brooklyn printing plant
owner very happy. Fluctuations in heat
and humidity in his plant had caused the
dimensions of the printing paper to keep
altering slightly, enough to ensure a misalignment of the colored inks. The new
air conditioning machine created a stable
Willis Haviland Carrier
environment and aligned four-color
printing became possible. All thanks to the new employee at the
Buffalo Forge Company, who started on a salary of only $10 per week.
The ‘Apparatus for Treating Air’ (U.S. Pat# 808897) granted in
1906, was the first of several patents awarded to Willis Haviland
Carrier. The recognized ‘father of air conditioning’ is Carrier, but the
term ‘air conditioning’ actually originated with textile engineer,
Stuart H. Cramer. Cramer used the phrase ‘air conditioning’ in a 1906
patent claim filed for a device that added water vapor to the air in
textile plants—to condition the yarn.
In 1911, Willis Haviland Carrier disclosed his basic Rational
Psychrometric1 Formulae to the American Society of Mechanical
Engineers. The formula still stands today as the basis in all fundamental calculations for the air conditioning industry. Carrier said he
received his ‘flash of genius’ while waiting for a train. It was a foggy
night and he was going over in his mind the problem of temperature
and humidity control. By the time the train arrived, Carrier had an
understanding of the relationship between temperature, humidity
and dew point.
Industries flourished with the new ability to control the temperature
and humidity levels during and after production. Film, tobacco, processed meats, medical capsules, textiles and other products acquired
significant improvements in quality with air conditioning. Willis and
six other engineers formed the Carrier Engineering Corporation in
1915 with a starting capital of $35,000 (1995 sales topped $5 billion).
The company was dedicated to improving air conditioning
technology.
In 1921, Willis Haviland Carrier patented the centrifugal refrigeration
machine. The ‘centrifugal chiller’ was the first practical method of
air conditioning large spaces. Previous refrigeration machines used
reci-procating-compressors (piston-driven) to pump refrigerant
(often toxic and flammable ammonia) throughout the system. Carrier
desig-ned a centrifugal-compressor similar to the centrifugal turning-
1
psy·chrom·e·ter n. : a hygrometer consisting essentially of two similar
thermometers with the bulb of one being kept wet so that the cooling that
results from evaporation makes it register a lower temperature than the dry
one and with the difference between the readings constituting a measure of
the dryness of the atmosphere. psy·chro·met·ric adj. psy·chrom·e·try n.
NOT TO BE CONFUSED WITH
psy·chom·e·try n. 1 : divination of facts concerning an object or its
owner through contact with or proximity to the object.
psy·cho·met·rics pl. n. but sing. in construction: the psychological
theory or technique of mental measurement
http://www.merriam-webster.com
Page 8
blades of a water pump. The result was a safer and more efficient
chiller.
Cooling for human comfort, rather than industrial need, began in
1924, noted by the three Carrier centrifugal chillers installed in the
J.L. Hudson Department Store in Detroit, Michigan. Shoppers
flocked to the air conditioned store. The boom in human cooling
spread from the department stores to the movie theaters, most notably
the Rivoli Theater in New York, whose summer film business
skyrocketed when it heavily advertised the cool comfort. Demand
increased for smaller units and the Carrier Company obliged.
In 1928, Willis Haviland Carrier developed the first residential
‘Weathermaker’, an air conditioner for private home use. The Great
Depression and then WW2 slowed the non-industrial use of air
conditioning. After the war, consumer sales started to grow again.
The rest is history, cool and comfortable history.
Willis Haviland Carrier did not invent the very first system to cool an
interior structure, however, his system was the first truly successful
and safe one that started the science of modern air conditioning.
Special thanks given to the Carrier Corporation
http://inventors.about.com/library/weekly/aa081797.htm
WILLIS CARRIER
by John H. Lienhard
It was a hot August day in San Antonio, Texas. I was there to name the
Milam Building as a Mechanical Engineering Landmark. I went from
the hot street into the cool halls of this fine old 21-story Art Deco
building. As if by magic, the weather changed from awful to pleasant
as I entered.
This was no ordinary magic. You see, this was the first airconditioned office building in the world.
Inside, I met representatives of the Carrier Corporation. They were
proud this day. In 1928, their company installed the original system
here. Of course everyone invoked the name of Willis Carrier.
Carrier’s mother had some of that creative magic. For she had a
mechanic’s instincts. Carrier learned about math and machines from
his mother.
Carrier was poor. He waited tables, earned scholarships, and sold
stereopticon slides to get through engineering school at Cornell. In
1901, he went on to work for the Buffalo Forge Company. There he
designed heating and cooling equipment.
He soon saw how little we knew about regulating the temperature and
humidity of air. He went to work on the problem. By 1911, he’d written
the science of psychrometry. It describes air temperature and
humidity.
But Carrier did much more. He’d already begun creating a technology
for controlling air condition. In 1907, Buffalo Forge saw the value of
his work. They formed The Carrier Air Conditioning Corporation of
America as a subsidiary.
Air conditioning spread across America. First theaters and churches.
Then more complex structures. If you’re old enough, you remember
the early air-conditioned movie theaters. They used to paint blue ice
cubes on their marquees.
Carrier died in 1950. Now the Houston temperature climbs. And I
too say “Thank God!” for the magic that makes this sultry climate
so pleasant—all year round.
Engines of Our Ingenuity, № 688
http://www.uh.edu/engines/epi688.htm