NED University of Engineering & Technology
Department of Mechanical Engineering
RAC and Heat Transfer Lab (ME-320)
ANNEXURES
A, B, C & D
Compiled by:
Mr. Muhammad Anique Azam
Research Assistant
Name
Year
Batch
Roll No.
Department
Annexure A: Basic Principles
A 1.1.
Objective
It is important to understand the basic working principles of the equipment we will be using in this
lab, before getting hands-on experience with the advanced physical equipment. This section will
take you through the previously acquired knowledge from the classroom with the intention to recap
and help you gain detailed insight of the real departure from ideal systems, physical limitations,
and industrial best practices. The primer also contains basic single function equipment as well.
A 1.2.
Vapor Compression Refrigeration System
1.2.1. Working Cycle
The standard vapor compression refrigeration cycle comprises four processes:
(i)
(ii)
(iii)
(iv)
Isentropic compression of saturated vapor
Heat rejection at constant pressure
Isenthalpic expansion of saturated liquid
Isothermal addition of heat at constant pressure.
The T-s and p-h plots of the cycle are shown below:
The actual cycle, however, would differ due to pressure drops in the condenser and evaporator,
sub cooling of the liquid at the condenser exit, superheating of the vapor at evaporator outlet, nonisentropic compression, etc. Some important relations can be found as under:
Refrigeration Effect = ℎ1 − ℎ4
Refrigeration Capacity = 𝑚̇(ℎ1 − ℎ4 )
𝑞̇ 𝐿
𝑚̇(ℎ1 − ℎ4 ) ℎ1 − ℎ4
=
=
𝑞̇ 𝐻 − 𝑞̇ 𝐿 𝑚̇(ℎ2 − ℎ1 ) ℎ2 − ℎ1
Power (in kW) per kW of refrigeration = Inverse of 𝐶𝑂𝑃𝑅
𝐶𝑂𝑃𝑅 =
1
𝐶𝑂𝑃𝑅
Refrigerating Efficiency= 𝐶𝑂𝑃
𝑅,𝐶𝑎𝑟𝑛𝑜𝑡
Ton of Refrigeration (TR): Originally 1TR was defined as the rate of heat transfer required to make
1 short ton (2000 lbs) of ice per day from water (latent heat of fusion=144 Btu/lb) at 0℃.
1TR = 200Btu/min =211kJ/min (3.5167 kW)
1.2.2. Main Components
The four main components are (i) Compressor, (ii) Condenser, (iii) Expansion device, and (iv)
Evaporator. The different classifications of each are discussed one by one.
1.2.3. Compressors
They can be classified as follows:
(a) On the basis of working principle: Positive displacement compressors (reciprocating,
rolling piston, rotary vane, single /twin screw, and scroll compressors) and Dynamic type
compressors (centrifugal and axial flow compressors).
Parts of a hermetic compressor: 1 Housing with connectors and baseplates, 2 Top Cover, 3 Block with stator bracket,
4 Stator (with screws), 5 Rotor, 6 Valve unit (screws, cylinder cover, gaskets, valve plate), 7 Crankshaft with grommet,
8 Connecting rod with piston, 9 Oil pick-up tube, 10Springs with suspensions, 11 Internal discharge tube (screw,
washer, gasket), 12 Start equipment (relay, cover, cord relief)
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(a)Rolling piston type rotary compressor, (b)Screw compressor, (c)Swash Plate Compressor, (d)
Scroll Compressor, (e)Reciprocating piston compressor
(b) On the basis of the arrangement of compressor motor
Left to right: Hermetic (or sealed), Semi-hermetic(or semi-sealed), Open type
1.2.4. Condensers
Condensers used in refrigeration systems can be classified into three broad categories (pictured
below), left top: air cooled, left bottom: water cooled, right: evaporative type.
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1.2.5. Expansion Device
In general, the expansion device serves to (a) reduce pressure from condenser pressure to
evaporator pressure, and (b) regulates the refrigerant flow from the high pressure liquid line into
the evaporator at a rate equal to the evaporation rate in the evaporator. Some commonly used
expansion devices are Capillary Tube, Automatic Expansion Valve (AEV or AXV), Thermostatic
Expansion Valve (TEV or TXV), Float Type Expansion Valve, and Electronic Expansion Valve.
Working and construction of Thermostatic Expansion Valve is shown under.
4
1.2.6. Evaporators
Two main types of evaporators employed are:
(a) Direct-expansion type in which the refrigerant boils inside the tubes, cooling the fluid (e.g.
air, water, brine) that passes over the outside of the tubes; in the case of a plate type
evaporator a solid product in direct contact with the plate is cooled by conduction. (Pictured
below – left to right: Roll bond evaporator, Finned tube coils, RS Type Evaporator)
(b) Flooded type in which the refrigerant vaporizes on the outside of the tubes, which are
submerged in liquid refrigerant within a closed shell. The fluid to be cooled flows through
the tubes. (Pictured below)
1.2.7. Auxiliaries
Some auxiliaries which do not affect the theoretical performance of a vapor compression system,
but have been either extensively used for their functionality or value addition, are listed as under:
(a) Thermostat: to switch operation upon achievement of desirable conditions.
(b) Sight Glass: to visually inspect operation and troubleshooting.
(c) Filter and/or Drier: to inhibit impurities either accumulated over time in the system or
residual water vapor/particulates in the refrigerant conduit, from entering constricted
passages (Expansion device) and working component (compressor).
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(d) Oil Separators: to separate compressor oil from refrigerant which usually circulates the
circuit near the compressor.
(e) Traps: to inhibit liquid refrigerant entering compressor.
(f) Pressure switch: to shut down the compressor in the event of unusual pressure
decrease/increase usually identifying leakage.
1.2.8. Refrigerants
Refrigerants are the working fluids employed in a vapor compression system. They can be
classified as:
(a) Primary refrigerants are those fluids, which are used directly as working fluids. These
fluids provide refrigeration by undergoing a phase change process in the evaporator.
(b) Secondary refrigerants are those fluids (predominantly liquids), which are used for
transporting thermal energy from one location to other. These refrigerants do not undergo
phase change as they transport energy from one location to other. The commonly used
secondary refrigerants are the solutions of water and ethylene glycol, propylene glycol or
calcium chloride. These solutions are known under the general name of brines.
1.2.9. Choice of a Primary Refrigerant
The selection of primary refrigerants is based on the consideration of the following aspects:
Thermodynamic characteristics
(i)
(ii)
(iii)
(iv)
(v)
High latent enthalpy of vaporization.
Low freezing temperature.
Relatively high critical temperatures.
Positive evaporating pressure.
Relatively low condensing pressure.
Physical and chemical characteristics
(i)
(ii)
(iii)
(iv)
High dielectric strength of vapor.
Satisfactory oil solubility.
Low water solubility.
Inertness and stability.
Safety
(i)
(ii)
Non flammability.
Nontoxicity.
Effect on the environment
(i)
(ii)
Ozone depletion potential (ODP)
Global warming potential (GWP).
Economics
The refrigerant used should preferably be in expensive and easily available.
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The chart below shows an interesting comparison among the common refrigerants in use.
1.2.10. ASHRAE Designation System
Fully saturated halogenated hydrocarbons are designated by R XYZ, where: No. of carbon (C)
atoms = X+1, No. of hydrogen (H) atoms = Y1, and No. of fluorine (F) atoms = Z. The balance
indicates the number of chlorine atoms. Only 2 digits indicates that the value of X is zero.
Organic refrigerants areas signed serial numbers in the 600 series.
Inorganic compounds are designated by adding 700 to their molecular mass.
A 1.3.
Dehumidification
1.3.1. A general mention
Humidity is the tiny amounts of water in the ambient air around us. While not only air can be
humid, any gas having trace amounts of water vapor in superheated state at the respective partial
pressure is considered to be humid. It is noteworthy that air can show a wide spectrum of humidity
at various geographical locations or ambient conditions, and the need to increase or decrease the
humidity levels varies drastically from application to application. A brief list of examples can be
numbered as under:
(a)
(b)
(c)
(d)
Grain Storage Silos – lesser values of humidity desirable.
Pharmaceutical manufacturing facility – lesser values of humidity desirable.
Greenhouses and drip irrigation facilities – higher values of humidity desirable.
General buildings – moderate values of humidity desirable
1.3.2. Humidity – Absolute or Relative
It is noteworthy that the literature exercises two frequently swappable terms of “relative humidity”
which is by default the synonym for layman term “humidity”, and, “absolute humidity”.
(a) The relative humidity is the amount of water vapors present in air relative to the maximum
amount of water that could have been in the air at saturation partial pressure.
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Mathematically, it is the ratio of partial pressure of water present in the air, to the
equilibrium pressure or the saturation pressure of water at the given temperature.
𝑅𝐻 = 𝜙 =
𝑝𝐻2 𝑂
𝑝𝑠𝑎𝑡@𝐷𝐵𝑇
(b) Absolute humidity is the “mass by mass” denotation of mass of water in the air per unit
mass of dry air. Changing temperature will not affect the absolute humidity of the system
if kept inside the psychrometric envelope.
𝐴𝑏𝑠. 𝐻𝑢𝑚. = 𝑤 =
𝑚𝐻2 𝑂
𝑚𝑑𝑟𝑦 𝑎𝑖𝑟
1.3.3. Dehumidifiers
Dehumidifiers, as the name suggests, dehumidify the air around us. The function of a dehumidifier
is to remove moisture from air. This is required to prevent or minimize the following:
(i) Physical discomfort & physiological problems like acute allergy & asthma.
(ii) Growth of bacteria, mold, fungus, mildew etc. on surfaces.
(iii)Accelerated corrosion of metal.
(iv) Degradation of surface finish.
(v) Malfunction of electronic/electrical equipment.
1.3.4. Types of dehumidifiers
Air around us inherently contains a small amount of water at all times. When subjected to cooling,
as what a large portion of HVAC&R deals with, the condensable water gets condensed.
The most common type of dehumidifiers employ a refrigeration cycle. Humid air is drawn over
air over cold evaporator coils, condensing out its moisture. It then passes over warm condenser
coils and back into the room. The condensed water drips into a container in the unit that has to be
emptied. The water can be directed to a drain by means of a hose. Mold can grow in the drainage
areas of a dehumidifier and regular cleaning of the water basin is required.
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A second type is the desiccant humidifier. The most critical component is the desiccant rotor. It is
about as wide as the dehumidifier itself and an inch or two thick. It is made up of alternate layers
of flat and corrugated sheets which are impregnated with the desiccant. These sheets are
arranged so that they allow for air flow perpendicular to the drum. The desiccant rotor has
two different zones – a “process zone” which makes up about 75% of the area of the rotor and a
“recharge zone” which makes up the remaining 25% of the rotor. The warm humid air that enters
the dehumidifier is pulled through the process zone. Here, moisture is adsorbed by the desiccant
material. The incoming humid air goes through the process zone and immediately exhausts out of
the dehumidifier.
Covering the recharge zone of the rotor is a heater. It warms circulated humid air which is pulled
back through the desiccant drum in the opposite direction of incoming humid air. This warm air
(heated by the heater) liberates moisture from the desiccant. Thus, moisture is transferred from the
desiccant to the air. The warm humid air that leaves the recharge zone enters the condenser on the
front of the dehumidifier. Here warm humid air condenses at room temperature. The condensate
drips down into a condensate collection bucket, much the same way as it does in a compressor
based dehumidifier.
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Commercial vs consumer grade desiccant dehumidifiers: Commercial desiccant dehumidifiers do
not work the same way that consumer grade desiccant dehumidifiers work. They share many of
the same parts (although the parts used on commercial units are much more heavy duty) and work
very similarly.
The primary difference between the two has to do with the warm humid air that leaves the recharge
zone of the desiccant rotor. As discussed above, this air is immediately funneled to a condenser on
a consumer grade desiccant dehumidifier. Here, the warm humid air condenses and the condensate
drips down into condensate collection bucket that can easily be removed from the dehumidifier.
Commercial units do not have a condenser. Instead, the warm moist air that leaves the recharge
zone of the desiccant drum is exhausted out of the building that is to be dehumidified through
ductwork. Thus, there is no condensate that forms anywhere in the system. This allows for
commercial units to dehumidify at even colder temperatures and even lower humidity than
residential consumer grade units.
Liquid desiccant systems are also employed where a liquid desiccant sprays through the air. The
recharge zone is separated as the brine is pumped between the two reservoirs.
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A 1.4.
Concept of Temperature
Based on the molecular theory, temperature has been defined as follows:
"Temperature indicates the speed of motion of the molecules" or "Temperature measures
the speed of motion of one molecule". [Ref: Modern Refrigeration & Air conditioning by
D. A. Thouse, C. H. Turnquist and A. F. Braciano, Goodhart -Wilcox, 2001.]
Since molecules in a system have different speeds, therefore a refined definition of
temperature can be "Average kinetic energy of the molecules of the system is regarded as
its temperature". As an exact definition is difficult to produce, more often it is regarded as
the degree of hotness and coldness of a system. [Ref: Thermodynamics: An Engineering
Approach by Y. A. Cengel, and M. A. Boles, McGraw Hill, 2001.]
A 1.5.
Temperature Measuring Devices
1.5.1. Liquid in Glass Thermometer
It is one of the most common types of temperature measuring devices.
Construction: A relatively large bulb at the lower portion of the thermometer hold the
major position of the liquid which expands when heated & rises in the capillary tube upon
which appropriate scale is marked. Alcohol and mercury are the most commonly used
liquids.
Operation: In operation, the bulb of the thermometer is in contact with the environment
whose temperature is measured. A rise in temperature causes the liquid to expand in the
bulb and rise in capillary tube thereby indicating the temperature. The expansion registered
by the thermometer is the difference between the expansion of the liquid and the glass.
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1.5.2. Mercury in Glass thermometer
They are usually applicable up to 600 ºF but their range may be extended to 1000 ºF by
filling the space above the mercury with a gas like nitrogen. This increases the pressure
and boiling point of the mercury and thereby permits the use of thermometer at high
temperature.
1.5.3. Bi-Metallic Strip
Construction: Two pieces of metals with different coefficients of thermal expansion are
bounded together to form the device.
Operation: When the strip is subjected to a temperature higher than the boiling
temperature it will bend in one direction, when it is subjected to a temperature lower than
the boiling point temperature it will bend in other direction. It has the advantage of low
cost, very low maintenance expenses and stable operation over extended periods of time.
1.5.4. Fluid Expansion thermometer
It is one of the most economical versatile and widely used device for industrial temperature
measurement application. A bulb containing a liquid, gas or vapor is immersed in the
environment. The bulb is connected by means of capillary tube to some type of pressure
measuring device such as bourdon gauge. An increase in temperature cause the liquid to
expand there by increasing the pressure is thus taken as an indication if the temperature.
1.5.5. Temperature Measurement by Electrical Effects
Electrical Resistance Thermometer or Resistance Thermometer Detector (RDT)
One quite accurate method of temperature measurement is the electrical resistance
thermometer. It consists of some type of resistive element which is exposed to the
temperature to be measured. The temperature is indicated through a measurement of the
change in the resistance of the element. Various methods are employed for construction of
resistance thermometer depending upon the application. In all cases care must be taken to
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ensure that the resistance wire is free of mechanical stresses and so mounted that moisture
cannot come in contact with the wire and influence the measurement.
1.5.6. Thermistors
It is a semi-conductor device that has a negative temperature coefficient of resistance in
contrast to the positive coefficient displayed by most materials.
1.5.7. Thermocouples
The most common electric method of temperature measurement uses the thermocouple
when two dissimilar metals are joined together.
1.5.8. Temperature measurement by radiation
The most common electric method of temperature measurement uses the thermocouple
when two dissimilar metals are joined together. Thermal radiation is electromagnetic
radiation emitted by a body as a result of its temperature. Thermal radiation lies in the
wavelength of about 0.1 - 1 00μm. It is possible to determine the temperature of a body
through a body through the measurement of thermal radiation emitted by a body. For this
purpose two methods are generally used, Optic Pyrometry and Emittance Determination.
1.5.9. Optic Pyrometry
This method refers to the identification of the temperature of a surface with the color of the
radiation emitted. As a surface is heated, it becomes dark, red, orange and finally white in
color. The maximum point in the black body radiation shifts to the shorter wavelength with
increase in temperature according to Wien's Law.
1.5.10. Emittance Determination
The temperature of a body may also be measured by determining the total emitted energy
from the body and then calculating the temperature. In practice optical pyrometry is the
most convenient method and widely used of the two radiation methods, for high
temperature.
A 1.6.
Thermal Energy Transfer in Solids
Thermal energy in solids is conducted by two modes:
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1.
2.
Lattice vibration.
Transport by free electron.
In good electric conductors a large number of free electrons move about the lattices structure of
the material. As these electrons may transport electric charge, they may also carry thermal energy
from a high temperature region to a low temperature zone.
Energy may also be transmitted as vibration energy in the lattice structure of the material. In
general, the amount of energy transferred in this mode is low as compared to the amount of energy
involved in electron transport. Due to this reason, almost all good electric conductors are good
heat carriers e.g., copper, aluminium, and silver. Similarly, good electrical insulations are usually
good heat insulations.
At high temperatures, the energy transfer through insulating materials may involve several modes:
1.
2.
3.
A 1.7.
Conduction through fibrous solid material
Conduction through the air trapped in the void spaces.
Radiation at sufficiently high temperature.
Insulations
Materials having very low thermal conductivity are termed as super-insulations. Basically thermal
insulations are materials used in the industries to resist the heat transfer. In their selection following
factors must be taken care of:
1.
2.
3.
4.
5.
6.
Efficiency (k).
Resistance to the temperature (Wide range of service temperature)
Resistance to corrosion (Moisture absorption, anti-fungi and bacteria, non¬combustible).
Resistance to shock and vibration (Shrinkage, good compressive strength).
Light weight (Less irritating & dusty).
Cost (Installation time, easy to fabricate).
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Generally, thermal insulation materials are grouped as follows:
1.
2.
3.
4.
5.
Low-temperature insulation material.
Insulation for building purposes.
Insulation for heating and process work.
Insulation for power generation field.
Refractory material.
1.7.1. Low-Temperature Insulation Materials:
These types of insulations are used to prevent heat transfer in low temperature services such as ice
and refrigeration plants. The materials generally have low thermal conductivity (k) value, i.e.
k=0.1 W/m K and temperature about up to-250ºC. The low temperature insulations are:
1.
2.
3.
4.
Cattle hair.
Wool felt.
Rubber (used in ice plants).
Polyurethane (in water coolers).
The important application of this type of insulation is the storage and transport of cryogenic liquids
like liquid hydrogen over extended period of time. Such applications have led to the development
of super insulation consisting of multiple layers of highly reflective materials separated by
insulated spaces. Other applications involve evacuation of entire system to minimize air
conduction and thermal conductivities as low as 0.3 m W/m K are possible.
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1.7.2. Insulations for Building Purposes:
These insulations are used to reduce the heat transfer from the building walls and roofs during cold
weather and heat production in hot weather. Materials include:
1.
2.
3.
4.
5.
Rock wool.
Slag wool.
Glass wool.
Cork.
Mineral fiber.
These insulations are applied in bulk form, blankets and spherical reinforced lattice. Metallic
reflecting type insulations are also used in this field. e.g. metal foil.
1.7.3. Insulations for Heating and Process Work:
These types of insulations have the temperature range from 150 ºF to 300 ºF or this purpose
asbestos paper, having low value of k and cost are advantageous in application. Asbestos paper is
not used at high temperatures because of the decomposition of the binder.
1.7.4. Insulations for Power Generation Field:
These types have the temperature range from 300 ºF to 600 ºF and the materials have higher
resistance to mechanical vibrations and shocks. Material is composed of 85% Mg and 15%
asbestos. Nowadays, Calcium Silicate is used efficiently in petrochemical industries and power
plants. Due to their wide temperature ranges Calcium Silicate is also called all-purpose insulation,
suitable for pipe work, boilers and all ancillary heat equipment.
1.7.5. High Temperature Insulating Material:
High temperature insulation materials have temperature range from 600 ºF to 900 ºF and are
composed of diatomacious earth and asbestos. This composition is capable to resist high
temperature. Diatomacious earth is excellent in insulating values temperature resistance, strength
and durability. An insulation consisting of one layer of diatomacious and a layer of 85%
magnesium is used for connecting high-temperature pipelines.
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1.7.6. Refractory Materials:
These are used in resisting high temperatures especially in the furnaces, like in blast furnace. They
have low k value and melting point to the range of 2000 °C to 3000 °C. The common types are
fire bricks, silica, etc.
A 1.8.
I.
II.
III.
IV.
V.
VI.
VII.
VIII.
IX.
X.
XI.
XII.
XIII.
XIV.
XV.
Practice Questions
Sketch a vapour compression cycle, on the p-h chart, taking into consideration the
following: subcooling of liquid at exit from condenser, superheating of vapour at exit from
evaporator, pressure drops in condenser and evaporator, and non-isentropic compression.
Concisely state the effect of above-listed factors on the COP of the system.
What is the difference between compressor “flooding” and “slugging”?
List the factors due to which the actual volumetric efficiency of a reciprocating compressor
is lower than its clearance volumetric efficiency.
What is the difference between internal and external equalization of a TEV?
Determine the chemical formula of R141
What would be the ASHRAE designation of CO2 as a refrigerant?
What is the difference between a flooded and a dry type evaporator?
By using Apparatus RAC100 determine the properties from the governing relations in
section 1.2.1
Draw a schematic of Apparatus RAC200 and identify auxiliaries, their usage with
justification of their respective positions.
Identify the type of Apparatus RAC300 as dehumidifier.
What type of evaporators do apparatus RAC100, RAC200 and RAC300 use?
What is the Seebeck Effect? How this effect is used in the construction and working of
thermocouples?
In optic pyrometry, how would you interpret the change in the brightness of a heated body?
In using different temperature scales how the Kelvin scale is better than the Celsius Scale?
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Annexure B1. Equipment RAC500 : Computerized AirConditioning Trainer
Before setting off for the practical and hands-on equipment handling, it is important to know the
equipment/apparatus on paper first.
B 1.1. Scope
Computerized Air-conditioning Trainer, Manfacturer: Elttronica Veneta, Manufacturer Model:
GCTC/EV, Laboratory Designation: RAC500. This equipment is used for Experiments 1, 2 and
3.
B 1.2. Equipment Introduction
This trainer is designed for an exhaustive study of the thermodynamic transformations the air
undergoes when crossing the various stages of a modern air conditioning unit that serves a room
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where temperature and relative humidity must be checked. Measuring air temperature and
humidity in different points enables to analyze air cooling, heating, humidification, and
dehumidification. Moreover some simulators of room and outdoor temperature and of room
humidity are included to verify the logic of control system in all the conditions that can occur in
an air handling unit.
The equipment is also provided with sensible and latent heat generators installed in the test room
that can be used to vary the thermal load in the same room and to check the response of the control
system. The controller includes the functions of calibration and control, as well as logical and
energy functions: thanks to an interface to a PC, it enables students to enter the points of the control
system, such as set points, measurement values, etc., via a PC (supplied on demand), so that any
alarm along the circuit can be detected and a different management of the system can be
programmed.
B 1.3. Technical Specifications
Power supply 230 Vac 50 Hz single-phase
Weight 235 kg
Dimensions 180 x 80 x 180 mm
B 1.4. Salient Features
This trainer allows to focus on the following arguments:
(i) Experimental study of the air psychrometric diagram
(ii) Study of the air transformations during its passage through the different unit sections
(iii)Calculation of the heat balances related to the air transformations
(iv) Checking of the behavior of the regulating system and of its effectiveness as function of
the thermal loads variation
The control system operates on the following components:
(i) Cooling and dehumidifying 1si and 2nd heating stage
(ii) 1st and 2nd humidifying stage Air dampers servo-command
(iii)The refrigerating unit including the compressor is independent and it is controlled by a
thermostat.
The control panel of the trainer includes a set of instruments for the data collection consisting of:
(i) 4 electronic thermometers
(ii) 4 electronic hygrometers
(iii)4 flow meters on the water circuit (cooling coil)
(iv) 3 multi meters
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B 1.5. Diagram and Parts
20
21
Air Circuit/Passage
Water Circuit
22
Primary Refrigerant Circuit
Water Heat Exchanger
23
Back-view
Simulator Room
24
B 1.6. Preliminary Checks on the System
The system starting must be preceded by the following tests:
Preliminary checking of the gas pressure in the refrigerating circuit.
When the equipment is off and the room temperature is equal to about 20 ℃, the gas pressure in
the refrigerating circuit must be equal to atleast 4 𝑏𝑎𝑟. On the contrary, a gas leakage from the
circuit should have taken place. If it is so, remove the covering panel of refrigerating unit, find out
the eventual leaks with a leakage detector and/or repeat the gas charging operation, respecting
what you find in the technical label of the equipment.
Preliminary checking on the calibration of the safety and control device.
The high pressure switch is usually calibrated at 15 𝑏𝑎𝑟 on system with HFC 134a for air or water
cooled condenser. The low pressure switch is adjusted for intervention pressure corresponding to
a saturation temperature which is 10 ℃ lower than the evaporation temperature.
Preliminary checking of the water pressure in the water circuit.
Before starting the equipment, the water pressure in the water circuit must be at least equal to 1
bar. On the contrary, removing the covering panel of the refrigerating unit, connect the charge
filling to water mains and charge water into the plant till recharging a pressure of 2 𝑏𝑎𝑟. Be careful
not to charge air into the plant. Notice that the pressure of the water mains must be 2 𝑏𝑎𝑟. In the
water circuit there is a mixture of water and antifreeze. During compressor operation the water
pressure decreases.
Preliminary checking of the air absence from the water circuit.
Remove the caps of the manual air venting wells set in the water tank and in the cooling coil. If
necessary, remove all the air present in the circuit.
Checking the electrical connection
Check electric connection and the protection devices of the electrical motor and the power supply
voltage.
The last must not exceed than ± 10% of the nominal value.
Feeding with the water
The tank of the humidifier must be filled by connecting the fitting behind the test room to the water
mains. Feeding with water, the tank of the latent load in the test room.
B 1.7. System Starting
(a) Check that, the safety push button is not pressed otherwise release it.
(b) The thermostat is properly adjusted, recommended set the point temperature 5 ℃.
(c) The taps of the hydraulic circuit are open. (Note that the system can run even when only
one rank of the cooling battery is enabled).
(d) Connect the trainer with the main via the cable of the equipment.
25
(e) Enable the magnetothermal differential switch.
(f) Press the start button,
(g) Power the pump.
(h) Power the compressor. (The compressor does not start if the pump is OFF)
(i) Power the fan and set a sufficient speed.
(j) Check that, the electrical instrument indicates congruent values.
(k) The line warning light is ON.
(l) The display of water thermostat is lit and indicates its temperature.
(m) The display of thermometer and hygrometer are lit and they indicate the value of
temperature and relative humidity.
(n) The pump warning light is ON.
(o) When the switches of the various components are enabled, the leads available in the
synoptic panel will be ON, otherwise there is some anomaly.
(p) Check the electrical connection using the electric diagram.
(q) When water is cooled, its volume as well as its pressure are reduced. In these conditions,
the minimum pressure of the water in the system must be equal to 1 bar.
(r) If the circulation pump does not start, check whether the rotor is locked. If this is the case,
unlock using a screwdriver and turning the fan of the electric motor in clockwise direction.
(s) If the pump is not able to start, check the contact of the flow switch or the fuses.
OUR LABORATORIES ARE OUR RESPONSIBILITIES. USE THE EQUIPMENT
PROPERLY AND FOR INTENDED PURPOSES.
26
Annexure B2. Equipment RAC600 : Cooling Tower Apparatus
Before setting off for the practical and hands-on equipment handling, it is important to know the
equipment/apparatus on paper first.
B 2.1. Scope
Cooling Tower Apparatus, Manfacturer: Elttronica Veneta, Manufacturer Model: CT/EV,
Laboratory Designation: RAC600. This equipment is used for Experiments 4 and 5.
B 2.2. Equipment Introduction
This equipment has been designed to experience with the construction principles and operational
characteristics of cooling towers and it mainly consists of a packed tower of transparent
methacrylate. The water heated in a tank is pumped to the top of the tower and its flow rate is
27
measured by a variable area flowmeter; then the water is distributed onto the packing uniformly to
avoid any “channeling” phenomenon.
The cooled water is collected at the tower bottom and then it is sent again to the heated tank. An
additional tank will keep the level of heated tank constant compensating the water lost by
evaporation. A forced air flow is blown by a centrifugal fan onto the column bottom; the flow rate
of air can be controlled by an air lock and measured by a diaphragm at the column top. After
leaving the packing, the air will cross a demister. The heated tank is equipped with 3 electric
heaters and with a safety thermostat. Process temperatures are measured by digital thermometers;
a differential pressure gauge will measure the pressure drops on the packing and on the diaphragm.
B 2.3. Technical Specifications
(a) Rectangular tower of Plexiglas; height of 550 𝑚𝑚
(b) 3 packings of different specific surface (92, 131 and 235 𝑚2 /𝑚3 ) being included in the
tower and easily interchangeable
(c) Additional water tank of Plexiglas, with capacity of 1 litre
(d) Centrifugal fan, with max. flow rate of 1340 𝑚3 /ℎ and maximum head of 80 𝑚𝑚𝐻2 𝑂
(e) Tank of AISI 304 stainless steel for hot water, with capacity of 9 litres and 3 electric heaters
of 500 𝑊
(f) Pump for water, 𝑄𝑚𝑎𝑥 = 3 𝑚3 /ℎ, 𝐻𝑚𝑎𝑥 = 5 𝑚𝐻2 𝑂
(g) Switchboard IP55, complying with EC standards and including digital thermostat, fan
controls, resistors and ELCB
(h) Power supply: 230 Vac 50 Hz single-phase - 2,6 kVA (Other voltage and frequency on
request) Dimensions: 100 × 650 × 1400 mm Weight: 72 kg
B 2.4. Salient Features
This trainer allows to focus on the following:
(i) Behaviour of different packings with different flow rates of air and water
(ii) Measurement of operational parameters in steady-state conditions
(iii)Representation of the state of the system on psychrometric chart and energy balance
(iv) Effect of the packing surface on the approach to wet bulb and on the pressure drops
(v) Performance with different cooling loads and inlet temperatures
The equipment houses:
(i) 6 digital thermometers with Liquid-Crystal Display (LCD)
(ii) Flowmeter, with range of 20-200 𝑙/ℎ
(iii)Inclined manometer, with range of 0-60 mm 𝐻2 𝑂
28
B 2.5. Diagram and Parts
Schematic
29
Packing
B 2.6. Preliminary Checks on the System
The system starting must be preceded by the following tests:
Hot and Make-up water reservoir.
Make sure the make-up water reservoir (D1) and the hot water reservoir (D2) is filled.
30
Safety Checks.
Ensure the electric plug is secure and tight. Do not turn on the heaters dry.
B 2.7. System Starting
(a) Place the unit on a strong table (the weight of the un it is 72 kg) in a place with a good air
circulation
(b) Check that the unit is level
(c) Close valve VJ
(d) Open partially valves V 1 and V2
(e) Fill the reservoirs of the wet bulb thermometers TIJ and Tr5 with water and ensure that the
gauze covering each of the wet bulb thermometers is thoroughly wetted
(f) Fill the hot water reservoir 02 with distilled water (necessary about 10litres) trough the
make-up tank 01 up to the mark
(g) Keep attention: the water level in the make-up reservoir DJ must be minimum 80 mm; if
there isn't water in D, do not switch on the heating elements J1, J2 and J3.
(h) Connect the unit with the electrical supply: single-phase + G
(i) To measure the pressure drop on the packing, open the two relative valves on the
differential manometer and close the others (see the labels)
(j) To measure the pressure drop on the orifice, open the two relative valves on the differential
manometer and close the others (see the labels)
(k) Switch on the E.L.C.B
(l) Set the thermostat TW2 at maximum 50°C (presetted at 40°C)
(m) Start the pump G I and then the heaters J I , J2 and J3
(n) Adjust the water flow rate using the valve V2 (for example at 1201/h)
(o) Switch on the fan P 1 and by means of the damper adjust the air now rate (for example at
ΔP = 16 mmH2O)
(p) Allow about 10 minutes for conditions to reach steady state
(q) Measure and record the process parameters
B 2.8. Shut down
(a) Switch off heaters J1, J2, J3
(b) After about 2 to 3 minutes, switch off the fan P1 and water pump G1.
(c) Switch off the E.L.C.B
(d) If the unit is idle for long period (more than 4-5 days), it should be completely drained
through valve V3.
OUR LABORATORIES ARE OUR RESPONSIBILITIES. USE THE EQUIPMENT
PROPERLY AND FOR INTENDED PURPOSES.
31
Annexure B3. Equipment HT100 : Linear Heat Conduction
Accessory
Before setting off for the practical and hands-on equipment handling, it is important to know the
equipment/apparatus on paper first.
B 3.1. Scope
Linear Heat Conduction Accessory, Manfacturer: Armsfield, Manufacturer Model: HT11,
Laboratory Designation: HT100. This equipment is used for Experiments 1, 2 and 3.
B 3.2. Equipment Introduction
The Armfield ‘Linear Heat Conduction’ accessory HT11 has been designed to demonstrate the
application of the Fourier Rate equation to simple steady-state conduction in one dimension. It
comprises a heating section (1) and cooling section (3) which can be simply clamped together or
clamped with interchangeable intermediate sections (2) sandwiched between them, as required.
Each interchangeable section contains a different specimen of metal conductor which allows a
plane wall of the same material, a plane wall of different cross section or composite walls with
different materials to be created for evaluation. The temperature difference created by the
application of heat to one end of the resulting wall and cooling at the other end results in the flow
of heat linearly through the wall by conduction. Measurement of the heat flow and temperature
gradient allows the thermal conductivity of the material to be calculated. The design allows the
conductivity of thin samples of insulating material to be determined.
B 3.3. Technical Specifications
(i) 30mm-long brass section of the same diameter as the heating and cooling sections and
fitted with two thermocouples at the same intervals. When this section is clamped between
32
the heating and cooling sections, a long plane wall of uniform material and cross-section
is created with temperatures measured at eight positions
(ii) Stainless-steel section of the same dimensions as the brass section to demonstrate the effect
of change in thermal conductivity
(iii)Aluminium section of the same dimensions as the brass section to demonstrate the effect
of change in thermal conductivity
(iv) 30mm-long brass section reduced in diameter to 13mm to demonstrate the effect of change
in cross-sectional area
(v) The heat-conducting properties of insulators may be found by simply inserting the paper
or cork specimens supplied between the heating and cooling sections
(vi) A tube of thermal paste is provided to demonstrate the difference between good and poor
thermal contact between the sections
Length: 0.43m, Width: 0.21m, Height: 0.29m
B 3.4. Salient Features
(i) Understanding the use of the Fourier rate equation in determining rate of heat flow through
solid materials
(ii) Measuring the temperature distribution for steady-state conduction of energy through a
uniform plane wall and a composite plane wall
(iii) Overall heat transfer coefficient for differing materials in series
(iv) Determining the constant of proportionality (thermal conductivity k) of different materials
(conductors and insulators)
(v) Relationship of temperature gradient to cross-sectional area
(vi) Effect of contact resistance on thermal conduction
(vii)
Understanding the application of poor conductors (insulators)
(viii)
Observing unsteady-state conduction (qualitative only)
B 3.5. Specimen
S
NO.
1
2
3
4
5
Specimen
Length
( mm )
Diameter
( mm)
Thermal
conductivity
W/m °C
Brass Specimen
30
25
110 – 128
Stainless Steel Specimen
30
25
25
Aluminium Alloy Specimen
30
25
180
Brass Specimen with reduce
diameter
30
13
110 – 128
Insulator
0.9
25
-
33
B 3.6. Diagram and Parts
34
MAIN PARTS
1. Heating section.
2. Interchangeable intermediate section .
3. Cooling section.
4. Water flow control valve.
5. Knob for regulating pressure.
6. Input for water.
7. Cold water pressure regulating valve.
8. Transparent filter bowl.
9. Drain/vent.
10. Samples of insulators.
11. Output for water.
12. Toggle clamp.
13. Base plate.
14. Connections for thermocouples.
15. Connection for heater
35
B 3.7. Operational Overview
Base Plate
The accessory is mounted on a PVC base plate (13). The intermediate sections (2) and samples of
insulators (10) are stored in recesses on the base plate when not in use.
Heating Section
The heating section is manufactured from 25 mm diameter cylindrical brass bar with a cartridge
type electric heating element installed at one end. Three thermocouples (T I, T2 and T3) are
positioned along the heated section at uniform intervals of 15 mm to measure the temperature
gradient along the section. The lead from the heating element (15) is connected to the DC outlet
socket marked OUTPUT 3 on the HTIOX.
Cooling Section
The cooling section is manufactured from 25 mm diameter cylindrical brass bar to match the
heating section and cooled at one end by water passing through galleries in the section. Three
thermocouples (T6, T7 and T8) are positioned along the cooling section at uniform intervals of 15
mm to measure the temperature gradient along the section.
Pressure Regulator
A pressure regulator (7) with integral filter (8) is incorporated to minimize the effect of fluctuations
in the supply pressure. A manual control valve (4) allows the flow of cooling water to be varied,
if required, over the operating range of 0 - 1.5 litres/min. The cold water supply is connected to
the serrated ferrule (6) on the side of the pressure regulator using reinforced flexible tubing.
Plastic Housings
The heating section, cooling section and all intermediate sections are located coaxially inside
plastic housings which provide an air gap and insulate the section to minimize heat loss to the
surroundings and prevent burns to the operator. A pair of toggle clamps (12) ensures that the
sections are held tightly together when in use. Two alternative studs are located on the heated
section to allow the clamp to operate with or without an intermediate section installed.
Thermocouples
All temperatures are measured using type K thermocouples each fitted with a miniature plug (14)
for direct connection to the front panel of the service unit HTI0X.
Intermediate Sections
The thermal conductivity of the Brass heating and cooling sections is typically in the range 110 to
128 W/m˚C over the range of operating temperatures in the HT11. Five intermediate sections (2)
are supplied.
36
Thermal Paste
The paste is applied between the adjacent faces to minimize the temperature gradient across the
joints. The effect of poor thermal contact between the sections can be demonstrated by taking
equivalent readings with no paste applied then with the sections unclamped.
When the Brass Specimen, which incorporates thermocouples, is clamped between the heated and
cooled sections the two thermocouples installed in the specimen assume the identities T4 and T5 to
provide a continuous plane wall with eight thermocouples TI – T8.
When the non-instrumented specimens or insulated disks are installed between the heated and
cooled sections, the temperature at the interfaces must be calculated from the temperature
measurements taken in the appropriate section. The thermocouples in each section are located 15
mm apart. T3 and T6 are located 7.5 mm away from the end surface.
OUR LABORATORIES ARE OUR RESPONSIBILITIES. USE THE EQUIPMENT
PROPERLY AND FOR INTENDED PURPOSES.
37
Annexure B4. Equipment HT200 : Radial Heat Conduction
Accessory
Before setting off for the practical and hands-on equipment handling, it is important to know the
equipment/apparatus on paper first.
B 4.1. Scope
Radial Heat Conduction Accessory, Manfacturer: Armsfield, Manufacturer Model: HT12,
Laboratory Designation: HT200. This equipment is used for Experiment 7.
B 4.2. Equipment Introduction
The Armfield 'Radial Heat Conduction' accessory has been designed to demonstrate the application
of the Fourier Rate equation to simple steady¬state conduction radially through the wall of a tube.
The arrangement, using a solid metal disk with temperature measurements at different radii and
heat flow radially outwards from the center to the periphery, allows the temperature distribution
and flow of heat by radial conduction to be investigated.
B 4.3. Technical Specifications
(i) The accessory comprises a solid disk of material, which is heated at the centre and cooled
at the periphery to create a radial temperature difference with corresponding radial flow of
heat by conduction.
38
(ii) Six K-type thermocouples are positioned at different radii in the heated disk to indicate the
temperature gradient from the central heated core to the periphery of the disk.
(iii)The radial distance between each thermocouple in the disk is 10mm.
(iv) Quick-release connections facilitate rapid connection of the cooling tube to a cold water
supply. A pressure regulator is incorporated to minimise the effect of fluctuations in the
supply pressure.
(v) A control valve permits the flow of cooling water to be varied, if required, over the
operating range of 0-1.5 l/min.
Length: 0.35m, Width: 0.18m, Height: 0.19m
B 4.4. Salient Features
(i) Understanding the use of the Fourier rate equation in determining rate of heat flow through
solid materials
(ii) Measuring the temperature distribution for steady-state conduction of energy through the
wall of a cylinder (radial energy flow)
(iii) Determining the constant of proportionality (thermal conductivity k) of the disk material
B 4.5. Diagram and Parts
39
MAIN PARTS
1. Cooling coil
2. Solid metal disk
3. Thermostat
40
4. Heating element
5. Central copper core
6. Plastic enclosure
7. Thermocouples
8. Electric connections to thermocouples.
9. Flow control valve
10. 1Drain/vent in front of pressure regulator
11. 1Transparent sheet to see the flow of water
12. Pressure regulator
13. Water Inlet
14. Knob for operating Pressure Regulator
15. Water Outlet
16. Electric Connection to heater
17. Base Plate
B 4.6. Operational Overview
The 'Radial Heat Conduction' accessory comprises a solid disk of material which is heated at the
centre and cooled at the periphery to create a radial temperature difference with corresponding
radial flow of heat by conduction.
Base plate
The accessory is mounted on a PVC base plate (17) which stands on the bench top alongside the
HT10X.
Heated Disk
The disk (2) is manufactured from brass 3.2 mm thick and 110 mm diameter with a central copper
core (5) 14 mm diameter. The thermal conductivity of the Brass disk is approximately 125 W/m˚C
at the typical operating temperatures in the HT12.
The entire radial specimen is located inside a plastic enclosure (6) which provides an air gap and
insulates the section to minimize heat loss to the surroundings and prevent burns to the operator.
Heating Element
The central core is heated by a cartridge type electric heating element (4) which is rated to produce
100 Watts nominally at 24 VDC. The lead from the heating element (16) is connected to the DC
outlet socket marked OUTPUT 3 (HT10X).
Cooling Coil
The periphery of the disk is cooled by cold water flowing through a copper tube (1) which is
attached to the circumference of the disk.
Thermocouples
Six type K thermocouples (7) are positioned at different radii in the heated disk to indicate the
temperature gradient from the central heated core to the cooled periphery of the disk. The
41
thermocouples are positioned on a tangent to the central heated core to minimize the disturbance
to the heat flow between the thermocouples.
The thermocouples are effectively positioned at the following radii from the center of the disk:
T1
7mm
T2
10mm
T3
20mm
T4
30mm
T5
40mm
T6
50mm
Each thermocouple is fitted with a miniature plug (8) for direct connection to the HT10X.
Tube Connectors
Quick-release connections allow rapid connection of the cooling tube to a cold water supply.
Pressure Regulator
A pressure regulator (12) is incorporated to minimize the effect of fluctuations in the supply
pressure.
Flow Control Valve
A manual control valve (9) allows the flow of cooling water to be varied, if required, over the
operating range of 0 - 1.5 liters/ min.
OUR LABORATORIES ARE OUR RESPONSIBILITIES. USE THE EQUIPMENT
PROPERLY AND FOR INTENDED PURPOSES.
42
Annexure B5. Equipment HT300 : Extended Surface Heat
Transfer Accessory
Before setting off for the practical and hands-on equipment handling, it is important to know the
equipment/apparatus on paper first.
B 5.1. Scope
Extended Surface Heat Transfer Accessory, Manfacturer: Armsfield, Manufacturer Model: HT15,
Laboratory Designation: HT300. This equipment is used for Experiment 8.
B 5.2. Equipment Introduction
The Armfield Extended Surface Heat Transfer Accessory HT15 has been designed to demonstrate
the temperature profiles and heat transfer characteristics for an extended surface (cylindrical pin)
when heat flows along the rod by conduction and heat is lost along the rod by combined convection
and radiation to the surroundings. It comprises a long horizontal rod, which is heated at one end to
provide an extended surface (cylindrical pin) for heat transfer measurements. Thermocouples at
regular intervals along the rod allow the surface temperature profile to be measured. By making
the diameter of the rod small in relation to its length, thermal conduction along the rod can be
assumed to be one-dimensional and heat loss from the tip can be ignored. The measurements
obtained can be compared with a theoretical analysis of thermal conduction along the bar combined
with heat loss (heat transferred) to the surroundings by the modes of free convection and radiation
simultaneously.
B 5.3. Technical Specifications
(i) A long horizontal rod, which is heated at one end, provides an extended surface (pin) for
heat transfer measurements.
(ii) Thermocouples at regular intervals along the rod allow the surface temperature profile to
be measured.
43
(iii)The rod is manufactured from brass and mounted horizontally with support at both ends
positioned to avoid the influence of adjacent surfaces. The rod is coated with a heatresistant matte black paint, which provides a consistent emissivity close to unity.
(iv) It is heated by an electric heating element, which operates at low voltage for increased
operator safety and is protected by a thermostat to prevent damage from overheating.
(v) Eight thermocouples are attached to the surface of the rod at equal intervals of 50mm,
giving an overall instrumented length of 350mm. Another thermocouple is mounted
adjacent to the heated rod to measure the ambient air temperature.
(vi) The heated end of the rod is mounted coaxially inside a plastic housing, which provides an
air gap and insulates the area occupied by the heater, in order to minimize heat loss and
prevent burns to the operator.
(vii)
The measurements obtained can be compared with a theoretical analysis of thermal
conduction along the bar combined with heat loss (heat transferred) to the surroundings by
the modes of free convection and radiation simultaneously.
Length: 0.50m, Width: 0.15m, Height: 0.15m
B 5.4. Salient Features
(i) Determining the combined heat transfer (𝑄𝑟𝑎𝑑𝑖𝑎𝑡𝑖𝑜𝑛 + 𝑄𝑐𝑜𝑛𝑣𝑒𝑐𝑡𝑖𝑜𝑛 ) from a horizontal
cylinder in natural convection over a wide range of power inputs and corresponding surface
temperatures
(ii) Measuring the domination of the convective heat transfer coefficient 𝐻𝑐 at low surface
temperatures and the domination of the radiation heat transfer coefficient 𝐻𝑟 at high surface
temperatures
(iii)Determining the effect of forced convection on the heat transfer from the cylinder at
varying air velocities
B 5.5. Diagram and Parts
44
MAIN PARTS
1. Support at tip.
2. Thermocouples.
3. Heated bar.
4. Thermostat.
5. Plastic housing
6. Electrical connection for heater.
7. Electrical heater.
8. Support at root.
9. Base plate.
10. Support for thermocouples.
11. Thermocouple to measure ambient temperature
B 5.6. Operational Overview
Heated Bar
The bar (3) is manufactured from a solid cylindrical brass bar with a constant diameter of 10 mm
and is mounted horizontally with a support (8) at the heated end and a steady (1) at the tip. The bar
is coated with a heat resistant matt black paint which provides a consistent emissivity close to unity
and is positioned to avoid the influence of adjacent surfaces. The thermal conductivity of the Brass
rod is approximately 121 W/m K at the typical operating temperatures in the HT 15.
The heated end of the bar is mounted co-axially inside a plastic housing (5) which provides an air
gap and insulates the area occupied by the heater to minimize heat loss and prevent burns to the
operator.
Electric Heater
45
The rod is heated by a cartridge type electric heating element (7) which operates at low voltage for
increased operator safety and is protected by a thermostat (4) to prevent damage from overheating.
Thermocouples
Eight K type thermocouples (2) are attached to the surface of the rod at equal intervals of 50 mm
giving an overall instrumented length of 350 mm. Each thermocouple is wrapped around the rod
to minimize errors by conduction. Thermocouple T1 measures the temperature at the hot end of the
rod and T8 measures the temperature at the tip. Thermocouple T9 is mounted adjacent to the heated
rod to measure the ambient air temperature.
OUR LABORATORIES ARE OUR RESPONSIBILITIES. USE THE EQUIPMENT
PROPERLY AND FOR INTENDED PURPOSES.
46
Annexure B6. Equipment HT400 : Combined Convection and
Radiation Accessory
Before setting off for the practical and hands-on equipment handling, it is important to know the
equipment/apparatus on paper first.
B 6.1. Scope
Combined Convection and Radiation Accessory, Manufacturer: Armfield, Manufacturer Model:
HT14, Laboratory Designation: HT400. This equipment is used for Experiment 9 and 10.
B 6.2. Equipment Introduction
The Armfeild ‘Combined Convection and Radiation’ accessory HT14 has been designed to
demonstrate how heat is transferred from a solid surface to its surroundings by the combined
modes of convection and radiation. In practice these modes are difficult to isolate and therefore an
analysis of the combined effects at varying surface temperature and air velocity past the surface
47
can be studied by HT14.The heated surface studied is a horizontal cylinder which can be operated
in free convection or forced convection when located in the stream of moving air. Measurement
of the surface temperature of the uniformly heated cylinder and the electrical power supplied to it
allows the combined effects of convection and radiation to be compared with theoretical values.
The dominance of convection at lower surface temperature and dominance of radiation at higher
surface temperature can be demonstrated as can the increase in heat transfer due to forced
convection..
B 6.3. Technical Specifications
(i) This Armfield accessory has been designed to demonstrate the laws of radiant heat transfer
and radiant heat exchange using light radiation to complement the heat demonstrations,
where the use of thermal radiation would be impractical.
(ii) The equipment consists of a centrifugal fan with a vertical outlet duct. At the top of the
duct there is a heated cylinder. The mounting arrangement for the cylinder in the duct is
designed to minimize loss of heat by conduction to the wall of the duct.
(iii)The surface of the cylinder is coated with heat-resistant paint which provides a consistent
emissivity close to unity. A K-type thermocouple (T10) attached to the wall of the cylinder,
at mid position, enables the surface temperature to be measured under the varying operating
conditions.
(iv) A variable-speed fan blows air through the outlet duct and a vane-type anemometer within
the fan outlet duct enables the air velocity in the duct to be measured. On the HT14C the
fan is a variable-speed fan with electronic control.
(v) On HT14 a manually adjustable throttle plate permits the air velocity to be varied. A Ktype thermocouple (T9) in the outlet duct allows the ambient air temperature to be
measured upstream of the heated cylinder.
Length: 0.35m, Width: 0.30m, Height: 1.2m
B 6.4. Salient Features
(i) Determining the combined heat transfer (𝑄𝑟𝑎𝑑𝑖𝑎𝑡𝑖𝑜𝑛 + 𝑄𝑐𝑜𝑛𝑣𝑒𝑐𝑡𝑖𝑜𝑛 ) from a horizontal
cylinder in natural convection over a wide range of power inputs and corresponding surface
temperatures
(ii) Measuring the domination of the convective heat transfer coefficient 𝐻𝑐 at low surface
temperatures and the domination of the radiation heat transfer coefficient 𝐻𝑟 at high surface
temperatures
(iii)Determining the effect of forced convection on the heat transfer from the cylinder at
varying air velocities
48
B 6.5. Diagram and Parts
49
MAIN PARTS
1. Base Plate
2. Thermal Switch
3. Supply to fan
4. Bottom Tubular Duct
5. Anemometer
6. Top Tubular Duct
7. Heated cylinder
8. Guard to protect inadvertent contact with heated cylinder
9. Locking screw for changing the position of thermocouple
10. Index mark to show the datum position of thermocouple
11. Electrical connection for heating element
12. Thermocouple indicating temp. of heated cylinder
13. Electrical connection of Anemometer
14. Thermocouples indicating temp. of ambient air
15. Centrifugal fan
16. Screw for adjusting air velocity
17. Throttle plate
18. Electrical connection of fan
B 6.6. Operational Overview
The `Combined Convection and Radiation' accessory comprises a centrifugal fan (15) with a
vertical outlet duct (4 and 6) at the top of which is mounted a heated, horizontal cylinder (7). A
thermocouple attached to the wall of the heated cylinder provides a measurement of the surface
temperature from which heat transfer calculations can be performed.
Base plate
The accessory is mounted on a PVC base plate (1) which stands on the bench top alongside the
HT 10X.
Heated Cylinder
The heated cylinder (7) has an outside diameter of 10 mm, a heated length of 70 mm and is
internally heated throughout its length by an electric heating element. The surface of the cylinder
is coated with heat resistant paint which provides a consistent emissivity close to unity.
The heated cylinder is mounted in such a way that the body can be rotated to allow the
position of the thermocouple to be varied and the temperature distribution around the surface of
the cylinder to be determined. An insulated cover allows the hot cylinder to be rotated and a locking
screw (9) allows any position to be retained. The position of the thermocouple on the heated
cylinder is indicated by a dot on the end of the
insulated cover. An index mark (10) on the side of the boss shows the datum position for the
thermocouple. The inside diameter of the duct is 70 mm
50
Heating Element
The heating element is rated to produce 100 Watts nominally at 24 VDC into the cylinder. The
electrical connections to the cylinder incorporate temperature resistant insulation with plug
connection ( I I) to the variable 24 Volt DC supply socket marked OUTPUT 3 on HT10X.
Cylindrical Duct
The cylindrical duct is fabricated in two parts (4 and 6) with a rotating vane type anemometer (5)
mounted between the two sections to allow the velocity of the air approaching the heated cylinder
to be measured.
A guard (8) covering the outlet from the vertical duct prevents inadvertent contact with the heated
cylinder or the hot wall of the duct when the accessory is in use or cooling down following
operation.
Anemometer
The lead from the anemometer (13) connects directly to the socket marked Ua on the HT10X to
provide readings of air velocity directly in units of m/sec. The operating range of the anemometer
is 0 - 10 m/sec.
Fan
The centrifugal fan (15) is mounted at the base of the cylindrical duct (4). In normal operation the
maximum air velocity is approximately 8 m/sec when the fan is operated from a 50 Hz electrical
supply. A thermal switch (2) protects the fan against over current, in the event of a fault condition,
and allows the fan to be switched off for free convection demonstrations.
Throttle Plate
A variable throttle plate (17) at the inlet to the fan allows the velocity of the air through the outlet
duct to be varied by adjusting the screw (16) at the centre of the front of the plate. The centrifugal
fan is mains operated and obtains its supply from a mains outlet (OUTPUT 1) at the rear of the
service unit. The connecting lead (18) is connected to this socket on the HT10X.
Thermocouple T9
Thermocouple T9 is fitted in the wall of the duct, upstream of the anemometer to measure the
temperature of the air upstream of the heated cylinder. This thermocouple is fitted with a miniature
plug (14) for direct connection to the HT10X. The resolution of the temperature reading is 0.1°C.
Thermocouple T10
Thermocouple T 10 is attached to the wall of the heated cylinder to indicate the surface temperature
of the cylinder mid way along the cylinder. This type K thermocouple is fitted with a standard plug
(12) for direct connection to the HT10X service unit. The resolution of the temperature reading is
1°C.
51
B 6.7. Nomenclature
The nomenclature associated with the experiments using this apparatus is as under:
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52
Annexure B7. Equipment HT500 : Radiation Errors in
Temperature Measurement Accessory
Before setting off for the practical and hands-on equipment handling, it is important to know the
equipment/apparatus on paper first.
B 7.1. Scope
Radiation errors in temperature measurement accessory, Manufacturer: Armfield, Manufacturer
Model: HT16, Laboratory Designation: HT500. This equipment is used for Experiment 11 and 12.
B 7.2. Equipment Introduction
The Armfield 'Radiation Errors in Temperature Measurement' accessory HT16 has been designed
to demonstrate how temperature measurements can be influenced by sources of thermal radiation.
Radiative heat transfer between a thermometer and its surroundings may significantly affect the
temperature reading obtained from the thermometer, especially when the temperature of a gas is
to be measured while the thermometer 'sees' surrounding surfaces at a higher or lower temperature
than the gas. The error in the reading from the thermometer is also affected by other factors such
as the gas velocity past the thermometer, the physical size of the thermometer and the emissivity
of thermometer body.
53
B 7.3. Technical Specifications
(i) In this equipment a group of thermocouples are used to measure the temperature of a stream
of air at ambient temperature, passing through the centre of a duct while the wall of the
duct is elevated in temperature to subject the thermocouples to a source of thermal
radiation.
(ii) Radiative heat transfer between a thermometer and its surroundings may significantly
affect temperature readings obtained from the thermometer, especially when the
temperature of a gas is to be measured while the thermometer ‘sees’ surrounding surfaces
at a higher or lower temperature than the gas.
(iii)The error in the reading from the thermometer is also affected by other factors such as the
gas velocity over the thermometer, the physical size of the thermometer and the emissivity
of the thermometer body. In this equipment a group of thermocouples are used to measure
the temperature of a stream of air, at ambient temperature, passing through the centre of a
duct while the wall of the duct is elevated in temperature to subject the thermocouples to a
source of thermal radiation.
(iv) Each thermocouple gains heat by radiation from the heated wall and loses heat by
convection to the air stream and conduction along the wire. The net result is an increase in
the temperature of the thermocouple above the temperature of the air stream it is supposed
to measure. The result is an error in the reading from the thermocouple. A radiation shield
can be positioned in the duct to show the effect of screening the thermocouples from
thermal radiation from the duct wall.
(v) The effect of air velocity past the test thermocouples can be demonstrated by adjusting the
air flow. On HT16 the fan is fixed-speed with a manually adjustable throttle plate.
(vi) A vane-type anemometer within the fan outlet duct enables the air velocity through the
heated section to be measured.
(vii)
A radiation shield, which remains close to the air temperature, can be raised or
lowered over the thermocouples to demonstrate the change in readings when a radiation
shield is used.
Length: 0.35m, Width: 0.30m, Height: 1.22m
B 7.4. Salient Features
(i) Errors associated with radiative heat transfer
a. Effect of wall temperature on measurement error
b. Effect of air velocity on measurement error
c. Effect of thermocouple style on measurement error
(ii) Methods for reducing errors due to radiation:
a. Design of a radiation-resistant thermometer
b. Use of a radiation shield to surround the thermometer
54
B 7.5. Diagram and Parts
55
MAIN PARTS
1. Base Plate
2. Supply to fan
3. Thermal Switch
4. Bottom Tubular Duct
5. Anemometer
6. Top Tubular Duct
7. Electric Band Heater
8. Radiation Shield
9. Lever for varying the position of Radiation Shield
10. Thermocouples indicating temp. of air passing through heated duct
11. Thermocouple indicating surface temp of heated duct wall
12. Electrical connection of Electric Band Heater
13. Electrical connection of Anemometer
14. Thermocouples indicating temp. of ambient air
15. Centrifugal fan
16. Screw for adjusting air velocity
17. Throttle plate
18. Electrical connection of fan
B 7.6. Operational Overview
The 'Radiation Errors in Temperature Measurement' accessory comprises a tubular metal duct (4
and 6) through which air, at ambient temperature, is blown vertically upwards by a centrifugal fan
(15). The velocity of the air can be changed by adjusting a throttle plate (17) at the fan inlet and
measured by an anemometer (5) in the fan outlet duct. Thermocouples indicate the wall
temperature at the heated end of the duct and the temperature of the air stream before it reaches
the heater section. Three test thermocouples are suspended at the centerline of the heated section.
A radiation shield may be positioned to shield these from the heated duct wall.
Electric Band Heater
A section of the duct wall is heated from the outside by an electric band heater (7) and provides
the source of radiation to three test thermocouples which are located on the centerline of the duct
adjacent to the heated section. The band heater is clamped onto the outside of the metal duct and
creates a heated length of 75 mm. The maximum surface temperature of the duct wall is 300°C
when operated in free convection at full heater power (fan not operating).
The power supplied to the heater can be varied and measured on the HT10X. The electrical
connections to the heater incorporate temperature resistant insulation with plug connection (12) to
the variable 24 Volt DC supply socket marked OUTPUT 3.
Insulated Jacket
56
The band heater and adjacent section of duct wall are covered by an insulated jacket which
minimises heat loss and prevents inadvertent contact with the band heater or the hot wall of the
duct when the accessory is in use or cooling down following operation.
Thermocouples
Thermocouple T10 is attached to the inside wall of the heated duct to indicate the surface
temperature of the wall at mid height in the heated section. This type K thermocouple is fitted with
a standard plug (11) for direct connection
to the HT10X service unit. The resolution of the temperature reading is 1°C.
Thermocouple T6 is fitted through the wall of the duct, below the anemometer to measure the
temperature of the air upstream of the heated section. This thermocouple is fitted with a miniature
plug (14) for direct connection to the HT10X service unit. The resolution of the temperature
reading is 0.1°C.
Three test thermocouples are located on the centreline of the duct adjacent to the heated section:
T7 Normal thermocouple bead 1.0 mm diameter with leads and bead polished.
T8 Same construction as T7 but leads and bead coated with black heat resistant paint to increase
the emissivity.
T9 Large thermocouple bead 3 mm diameter with leads insulated and bead coated with heat
resistant paint as T8.
Each type K thermocouple is fitted with a miniature plug (10) for direct connection to the HT10X
service unit. The resolution of the temperature readings is 0.1°C.
Radiation Shield
A radiation shield (8), by means of a lever (9), can be lowered over the test thermocouples to
demonstrate the improvement in reading accuracy when the thermocouples are shielded from the
source of radiation.
Baseplate
The accessory is mounted on a PVC baseplate (1) which stands on the bench top alongside the
HT10X.
Cylindrical Duct
The cylindrical duct is fabricated in two parts (4 and 6) and the heated section is incorporated at
the top of this cylindrical duct which is attached to the outlet of a centrifugal fan. The inside
diameter of the duct is 70 mm.
Anemometer
A rotating vane type anemometer (5) is mounted between the two sections of the cylindrical duct
to allow the velocity of the air approaching the heated section to be measured. The lead from the
57
anemometer (13) connects directly to the socket marked Ua on the HT10X to provide readings of
air velocity directly in units of m/sec. The operating range of the anemometer is 0 - 10 m/sec.
Throttle Plate
A variable throttle plate (17) at the inlet to the fan allows the velocity of the air through the outlet
duct to be varied by adjusting the screw (16) at the centre of the front of the plate.
Centrifugal Fan
The centrifugal fan is mains operated and obtains its supply from a mains outlet (OUTPUT 1) at
the rear of the service unit. The connecting lead (18) is connected to this socket on the HT10X.
A thermal switch (2) protects the fan against over current, in the event of a fault condition, and
allows the fan to be switched off when not required.
B 7.7. Nomenclature
Symbol
SI unit
Voltage to heated cylinder
V
V
Current to heated cylinder
Power supplied to heated cylinder
Air velocity in duct (free stream velocity)
Temperature of ambient air in duct
I
Qin
Ua
T6
A
W
m/sec
°C
Air temp measured by small, polished thermocouple
Air temp measured by small, black thermocouple
Air temp measured by large, black thermocouple
Surface temperature of heated duct wall
T7
T8
T9
T10
°C
°C
°C
°C
Name
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PROPERLY AND FOR INTENDED PURPOSES.
58
Annexure C1. Computational Tool: MATLAB
Computational tools require a good investment of time for qualifying to run operations on them
and get reliable results. This text will allow you gather insights into the basics of the program
MATLAB.
C1.1. Scope
MATLAB Package. This is a revision of the basic working and graphical user interface of the
program’s default configurations. It is advised that you go through the software at your own pace
and learn about the MATLAB environment in more detail.
C1.2. Open MATLAB
MATLAB is a powerful mathematical software package used by both engineers and
mathematicians in the workplace. The name stands for MATrix LABoratory. Originally designed
for manipulating matrices, MATLAB is great for many different mathematical tasks.
Some good reasons for learning MATLAB include:
i. You will gain a better insight into mathematical functions through complex graphing that
can’t easily be done by hand
ii. You can quickly find solutions to problems that take a long time by hand (like finding the
determinant of a 5x5 matrix)
iii. Later, you will be able to find approximate numerical solutions to problems that can’t be
solved by hand (like complicated integrals).
C1.3. MATLAB Desktop Layout
The MATLAB layout is divided into 4 windows (white area):
i. Command Window (centre), where you will type in all commands after the double arrow
“>>”
ii. Command History (bottom right), showing a history of commands in the order you typed
them.
iii. Workspace (top right), which will show your current variables. We will come back to this
when we introduce variables.
iv.
Current Folder (left) has a toolbar with your current directory shown. All your work will
be saved in this directory.
At the top of the screen in the grey coloured area you will see tabs Home, Plots and Apps. When
you start MATLAB it shows all menu items (modes) in Home tab grouped by their function. At
the bottom of grey coloured area you will see names of the functional groups for a particular tab.
59
C1.4. MATLAB Terminology
At the top of the screen you can see grey coloured area - the MATLAB Toolstrip.
The Toolstrip organizes MATLAB functionality in a series of tabs. Tabs are divided
into sections that contain a series of related controls. The controls are buttons, drop-down
menus and other user interface elements that you use to do things in MATLAB. For example, the
picture above shows the Home tab with sections for operations on Files, Variables, Code and
so forth. The File section has controls to do file related operations including creating scripts
(New Script), opening files (Open), and comparing two files (Compare). The light blue bar
in the upper right corner called the Quick Access Toolbar.
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C1.5. Global Tabs
When you open the MATLAB R2012b for the first time, you will notice three tabs -the Home tab, the Plots tab, and the Apps tab. These three tabs are always there no matter what
you are doing in MATLAB. For that reason, they are called global tabs. The Home tab, shown
below, is where you go to do general purpose operations like creating new files, importing data,
managing your workspace, and setting your Desktop layout.
The Plots tab, shown below, is where you go to create MATLAB Plots. The Plots tab displays a
gallery of plots available in MATLAB and any toolboxes that were installed. To create a plot from
the gallery, you select the variables in the Workspace that you want to plot and then select the
type of visualization you want to use for that data. The downward facing arrow on the far right
brings down the full extent of the plot gallery with many more choices. The gallery is smart, only
showing plots that are appropriate for the data that you've selected.
61
The last of the global tabs is the Apps tab, shown below. It is the place you go to run interactive
MATLAB applications. The Apps tab presents a gallery of installed applications. The
downward facing arrow on the far right brings down the full extent of the applications gallery
with many more choices. To start an application you simply click on the correspondent icon.
C1.6. Contextual Tabs
As we've seen, global tabs are always present regardless of what you are doing in MATLAB. In
addition to global tabs, the Toolstrip also has contexual tabs. Contextual tabs only appear when
you're doing certain things in MATLAB. Let's look at the Editor as an example. When you edit
a file, three new tabs appear -- the Editor tab, Publish tab, and View tab.
The Editor tab, shown below (on next page), contains all the functions you need when you're
editing your file. All of those great capabilities of the Editor are there organized in a way to make
them easier to find and use. This window opens over the Desktop layout.
In the upper right corner of the Editor window (and any other window) you will find Actions
button. After clicking on it and choosing Dock option the Command window area in the Desktop
becomes divided on two parts with the Editor window placed at the top and
the Command window at the bottom. If the Editor is docked in the Desktop, those tabs related
to the Editor appear next to the global tabs as shown below.
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Publishing is a very useful feature in MATLAB. The Publish tab takes all the formatting controls
you need to create beautiful MATLAB documents with publishing and puts them in a single place.
The View tab is the last of the Editor contextual tabs. It is where you go to control the layout
and appearance of files in the Editor. You'll also find contextual tabs in the Variable Editor.
These features of MATLAB will be discussed later in our practicals.
C1.7. Minimizing Toolstrip
To Minimize the Toolstrip right-click anywhere in the Toolstrip and select "Minimize Toolstrip"
or double-click on any of the tabs. To restore the Toolstrip right-click anywhere on the Toolstrip
and select "Restore Toolstrip" or double-click on any of the tabs. When the toolstrip is
minimized it looks like this:
C1.8. Understanding Desktop Layout
> Change your MATLAB Current Folder to a folder on your USB drive. The folder you choose
will be where your MATLAB documents are saved.
> To understand better the purpose of the three windows, type in the simple command 3+5 in
the Command Window and press enter.
63
> What happened in the Command, Command History and Workspace Windows?
> To understand better the purpose of the three windows, type in the simple command 3+5 in
the Command Window and press enter.
> What happened in the Command, Command History and Workspace Windows?
C1.9. MATLAB as a Calculator
MATLAB can be used as a powerful calculator. The following exercises demonstrate the order
in which MATLAB evaluates expressions. The following commands illustrate the order of
priority when evaluating expressions.
Before typing each command into your Command Window, think about what you expect the
answer to be. If the output differs from your expected answer, figure out why.
> Type in the following commands, pressing Enter after each one.
5*2+3
3+5*2
> What if instead, we want to add 3 to 5 and then multiply the result by 2? We can use brackets
to change the order of evaluation as MATLAB will evaluate the contents of each bracket pair
first.
> Type in the following line of code:
(3+5)*2
Coding tip: Many students have troubles matching bracket pairs. Experienced MATLAB users
reduce these errors by
1. typing both brackets ( ),
2. then using the back arrow key ← to move back and fill in the bracket contents (3+5).
> The following code is not valid. Type it in, press Enter, then read the error message and
change the code so that it works (note the vertical line pointing to the first error).
2(3-5)
Coding tip: The up-arrow key ↑ on the keyboard will recall a previous line for you to edit.
> Type in the following lines to figure out what the hat ^ key represents.
3^2
3^3
> Figure out the answers you would expect for the following two lines of code and then type
them in to verify your answer.
9-3^2
81/3^2
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C1.10. Mathematical Symbols in MATLAB
As we have just seen, the simplest mathematical operators are represented by the following
symbols.
Symbol Operator
Order Order of Priority
^
Raise to a power
1
evaluated first
*
Multiplication
2
evaluated after any powers
/
Division
2
evaluated after any powers
+
Addition
3
evaluated after any powers, multiplication and division
-
Subtraction
3
evaluated after any powers, multiplication and division
C1.11. Order of Operation
Operation order of Priority
i. The power operator has the highest order of priority.
ii. Multiplication and division both have equal 2nd order of priority.
iii. Addition and subtraction both have equal 3rd order of priority.
C1.12. Left to Right Rule
Expressions are evaluated from left to right: the leftmost operation is performed first and the
rightmost operation is performed last. However, note that the operator order of priority
supersedes the above left-to-right rule.
C1.13. Brackets
Round brackets, ( ), can be used to change the order of operations: any expression enclosed in
brackets will be calculated first.
> Type the following arithmetic expressions in the Command Window. Remember to mentally
calculate the answers before pressing the Enter key
(8+6)/(10-2^3)
8+6/(10-2^3)
8+6/10-2^3
Coding tip: The up-arrow ↑ on the keyboard will recall a previous line for you to edit.
The following expressions both have a value of 12.
> Type in the equivalent MATLAB expressions to obtain the correct answer using as few
pairs of brackets as possible.
172/3+3/4172/3+3/4 (needs 1 pair of brackets)
5+932+12(5−3)5+932+12(5−3) (needs 3 or 4 pairs of brackets)
C1.14. Elementary Math Functions
MATLAB has a number of built-in functions, such as square root, sine, cosine, exponential, etc,
functions. The following table gives a list of some commonly used functions. Later you will also
write your own functions.
65
round(x)
Rounds 𝑥 to the nearest integer
floor(x)
Rounds 𝑥 down to nearest integer
ceil(x)
Rounds 𝑥 up to nearest integer
rem(y,x)
Remainder after dividing 𝑦 by 𝑥 (eg remainder of 17/3 is 2)
sign(x)
Returns -1 if 𝑥 ; returns 0 if 𝑥 = 0; returns 1 if 𝑥 > 0.
rand or rand(1)
Generates a random number between 0 and 1
exp(x)
Exponential function 𝑒 𝑥
log(x)
Natural logarithm function, y=ln(x) (where 𝑒 𝑦 = 𝑥 )
sqrt(x)
Square root function, √𝑥
abs(x)
Absolute value function, |𝑥 |
sin(x)
sine function sin 𝑥
cos(x)
cos function cos 𝑥
tan(x)
tan function tan 𝑥
C1.15. Using Mathematical Functions
> Let 𝑥 = 1.2 , Verify that the following expressions have the values shown, by typing in
the correct MATLAB commands.
Mathematical expression
1
√2𝜋
1 2
𝑒 −2𝑥
Answer MATLAB command/Tips
0.1942 1/sqrt(2*pi)*exp(-0.5*1.2^2)
3
√(5 + cos 4𝑥)
| sin 3𝑥|
sin2 𝜋𝑥
𝑒 sin 𝑥
√𝑥 2 + 1
1
𝑥 arctan 𝑥 − ln(1 + 𝑥 2 )
2
3.8866
(5+cos(4*1.2))^(1/3)/abs(sin(
3*1.2))
0.3455 Sets of brackets required: 1
1.6259 Sets of brackets required: 3
Note: you will need to look up the
arctangent function in the MATLAB help
0.6053
files (click on Help at the top menu). Sets
of brackets required: 3
66
The above text has been referred for students from:
https://lo.unisa.edu.au/mod/book/tool/print/index.php?id=466676
OUR LABORATORIES ARE OUR RESPONSIBILITIES. USE THE AUXILLIARIES
TO THIS SOFTWARE PRACRICE PROPERLY AND FOR INTENDED PURPOSES.
67
Annexure C2. Computational Tool: Hourly Analysis Program
(HAP)
Computational tools require a good investment of time for qualifying to run operations on them
and get reliable results. This text will allow you gather insights into the basics of the program HAP.
C2.1. Scope
Hourly Analysis Program, Carrier Corporation, United Technologies. The following text shows
the basic working and graphical user interface of the program’s default configurations. It is advised
that you go through the software at your own pace and learn about the HAP environment in more
detail.
C 2.2. HAP System Design Features
HAP estimates design cooling and heating loads for commercial buildings in order to determine
required sizes for HVAC system components. Ultimately, the program provides information
needed for selecting and specifying equipment. Specifically, the program performs the following
tasks:
i. Calculates design cooling and heating loads for spaces, zones, and coils in the HVAC
system.
ii. Determines required airflow rates for spaces, zones and the system.
iii. Sizes cooling and heating coils.
iv.
Sizes air circulation fans.
v. Sizes chillers and boilers.
C 2.3. HAP Energy Analysis for Detailed Design
This section describes in conceptual terms how to use HAP to perform an energy analysis in the
detailed design phase of a project. Application of these concepts will be demonstrated in the handson experiment. Analysis work requires a general five step procedure.
Note that certain steps below are identical or similar to those used for system design. If a system
design has already been performed for a building, all of the data entered for design can be reused
for the energy analysis, and this significantly reduces the effort needed to complete the energy
analysis.
1) Define the Problem: First define the scope and objectives of the energy analysis. For example,
what type of building is involved? What type of systems and equipment are required? What
alternate designs or energy conservation measures are being compared in the analysis?
2) Gather Data: Before energy simulations can be run, information about the building, its
environment, HVAC and non-HVAC equipment, and its energy prices must be gathered. This
step involves extracting data from building plans, evaluating building usage, studying HVAC
system needs and acquiring utility rate schedules. Specific types of information needed
include:
i. Climate data for the building site.
ii. Construction material data for walls, roofs, windows, doors, exterior shading devices and
floors, and for interior partitions between conditioned and non-conditioned regions.
iii. Building size and layout data including wall, roof, window, door and floor areas, exposure
orientations and external shading features.
iv.
Internal load characteristics determined by levels and schedules for occupancy, lighting
systems, office equipment, appliances and machinery within the building.
68
v.
vi.
vii.
viii.
Data for HVAC equipment, controls and components to be used.
Data for chilled water, hot water and/or steam plants, if applicable.
Data for non-HVAC energy-consuming equipment.
Utility rate information for electric service and any fuel sources used in the building.
3) Enter Data Into HAP. Next, use HAP to enter data for the analysis. When using HAP, your
base of operation is the main program window. From the main program window, first create a
new project or open an existing project. Then define the following types of data which are
needed for energy analysis work:
a) Enter Weather Data. Weather data defines the temperature, humidity and solar radiation
conditions the building encounters during the course of a year. These conditions play an
important role in influencing loads and system operation throughout the year. Both design
and simulation weather data are needed. To define design weather data, a city can be chosen
from the program's weather database, or weather parameters can be directly entered.
Simulation weather is selected by loading a simulation weather file from the library
provided with the program or importing data from an external source. This step is also used
to define the calendar for your simulation year. All three types of data are entered using the
weather properties window.
b) Enter Space Data. A space is a region of the building comprised of one or more heat flow
elements and served by one or more air distribution terminals. Usually a space represents a
single room. However, the definition of a space is flexible. For some applications, it is more
efficient for a space to represent a group of rooms or even an entire building. To define a
space, all elements which affect heat flow in the space must be described. Elements include
walls, windows, doors, roofs, skylights, floors, occupants, lighting, electrical equipment,
miscellaneous heat sources, infiltration, and partitions.
While defining a space, information about the construction of walls, roofs, windows, doors
and external shading devices is needed, as well as information about the hourly schedules
for internal heat gains. This construction and schedule data can be specified directly from
the space input window (via links to the construction and schedule windows), or alternately
can be defined prior to entering space data.
Space information is stored in the project database and is later linked to zones in an air
system.
c) Enter Air System Data. An Air System is the equipment and controls used to provide
cooling and heating to a region of a building. An air system serves one or more zones. Zones
are groups of spaces having a single thermostatic control. Examples of systems include
central station air handlers, packaged rooftop units, packaged vertical units, split systems,
packaged DX fan coils, hydronic fan coils and water source heat pumps. In all cases, the air
system also includes associated ductwork, supply terminals and controls. In the case of
packaged DX, split DX, electric resistance heating and combustion heating equipment, the
system also encompasses this DX or heating equipment. For example, when dealing with a
gas/electric packaged rooftop unit, the "air system" includes the DX cooling equipment and
the gas heating equipment.
To define an air system, the components, controls and zones associated with the system
must be defined as well as the system sizing criteria. For energy analyses, performance
information about DX cooling equipment and electric and combustion heating equipment
must also be defined. All of this data is entered on the air system input window.
69
d) Enter Building Data. A Building is simply the container for all energy-consuming
equipment included in a single energy analysis case. One Building is created for each design
alternative being considered in the study. Building data consists of lists of plants and
systems included in the building, utility rates used to determine energy costs and data for
non-HVAC energy or fuel use. Data is entered using the building window.
4) Use HAP to Generate Simulation Reports. Once all input data has been entered, HAP can
be used to generate simulation reports. To generate building simulation reports, go to the main
program window and select the desired buildings. If data for a single building is being
evaluated, select only one building. If energy use and costs for a number of alternatives is being
compared, select a group of buildings. Next choose the “Print/View Simulation Results” option
on the Reports Menu. This displays the Building Simulation Reports Selection window.
Choose the desired reports. Then press Preview to display the reports or press Print to directly
print the reports. If system, plant or building calculations are needed to supply data for your
reports, HAP will automatically run these calculations first. Otherwise, if no calculations are
needed the reports will be generated immediately.
Simulation reports for individual air systems and plants included in your analysis can also be
generated. Use the same procedure but select air system or plant items instead. System and
plant simulation reports provide more detailed performance information for individual pieces
of equipment. They are often useful for learning about equipment performance and for
troubleshooting unexpected results.
5) Evaluate Results. Finally, use data from the simulation reports you generated to draw
conclusions about the most favorable design alternative. In many cases energy use and energy
cost data will be used for further study of lifecycle economics.
C 2.4. Working with Main Program Window
This section discusses HAP’s main program window which appears when you start the program.
Much of the work you will perform entering data and generating reports is done using features of
the main program window. Key elements and features of the main program window are discussed
below. Appendix A explains how to use these features in greater detail. The HAP main program
window consists of six components used to operate the program.
1) The Title Bar lists the program name and the name of the current project.
2) The Menu Bar lies immediately below the title bar. The menu bar contains seven pull-down
menus used to perform common program tasks.
i) The Project Menu provides options for manipulating project data. This includes tasks such
as creating, opening, saving, deleting, archiving and retrieving projects.
ii) The Edit Menu contains options used to work with individual data items such as spaces,
systems, walls, roofs, etc…
iii) The View Menu offers options used to change the appearance of the main program window.
This includes changing the format of data shown in the list view, turning on or off the toolbar
and status bar, and setting user preferences such as units of measure
iv) The Reports Menu provides options for generating reports containing input data, design
results and energy simulation results
v) The Wizards Menu contains options for running the Weather, Building, Equipment or
Utility Rate Wizards separately, and for running a "Full Wizard Session" which integrates
all four Wizards so you can rapidly generate data for a cost comparison study all at one
time.
vi) The Documentation Menu contains resource material to aid in learning about the program.
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vii) The Help Menu contains options for technical assistance with the program.
3) The Toolbar lies immediately below the menu bar and contains a series of buttons used to
perform common program tasks. Each button contains an icon which represents the task it
performs. These tasks duplicate many of the options found on the pull-down menus.
4) The Tree View is the left-hand panel in the center of the main program window. It contains a
tree image of the major categories of data used by HAP. The tree view acts as the “control
panel” when working with program data.
5) The List View is the right-hand panel in the center of the main program window. It contains a
list of data items in alphabetical order for one of the categories of data in your project.
6) The Status Bar is the final component of the main program window and appears at the bottom
of the window. The current date and time appear at the right-hand end of the status bar.
Pertinent messages appear at the left-hand end of the status bar.
C 2.5. Working with HAP input windows
While much of your work with the program is done on the main program window, the actual entry
of data is done using input windows. An input window appears when you choose to create a new
item or edit an existing item.
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The basic architecture of the software should enable you to follow the direction of your
instructor.
The above text has been referred for students from “Carrier Corporation HAP Quick Reference
Guide.”
OUR LABORATORIES ARE OUR RESPONSIBILITIES. USE THE AUXILLIARIES
TO THIS SOFTWARE PRACRICE PROPERLY AND FOR INTENDED PURPOSES.
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Annexure D: Tables and Charts
D 1.1. Values of c and n against Rayleigh Number
𝑹𝒂𝑫
10−9 𝑡𝑜 10−2
10−2 𝑡𝑜 102
102 𝑡𝑜 104
104 𝑡𝑜 107
107 𝑡𝑜 1012
𝒄
0.67
1.02
0.85
0.48
0.12
𝒏
0.058
0.148
0.188
0.250
0.333
D 1.2. Compressor Working Ranges
D 1.3. Charts
On Next Pages
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(SI Units)
Pressure-Enthalpy Diagram
HFC-134a
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