Refrigeration fundamental

REFRIGERATION / AIR CONDITIONING
FUNDAMENTALS & BASIC COMPONENTS
Package No: NR 145
HVAC &Refrigeration, Ultimo 2005 Refrigeration Fundamentals
Compiled by Peter Lamond with assistance from Greg Riach and Robert Baker.
Editing and computer generated graphics by D. Magyar
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REFRIGERATION / AIR CONDITIONING
FUNDAMENTALS & BASIC COMPONENTS
Package No: NR 145
Nominal Student Hours: Flexible.
Delivery: Competence in this training program can
be achieved through either a formal
education setting or in the workplace
environment.
Recognition of Prior Learning: The student / candidate may be granted
recognition of prior learning if the
evidence presented is authentic and valid
and covers the content as laid out in this
package.
Package Purpose: In this program students will study the
Principles of Refrigeration as applied to
the vapour compression cycle. Identify,
list and describe the function and
operation of the Major Components and
Flow Controls as utilised in the Vapour
Compression System. Additionally,
students are introduced to the basic
Fundamentals of Air Conditioning and
associated processes.
Suggested Resources: Boyle G., Australian Refrigeration and
Air Conditioning (ARAC) Volumes 1 &
2, 4th edition, WestOne Services.
Assessment Strategy: The assessment of this package is holistic
in nature and requires the demonstration
of the knowledge and skills identified in
the package content. To be successful in
this package the student must show
evidence of achievement in accordance
with the package purpose.

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Additional Resources:
Althouse A. D., Turnquist C. H., Bracciano A.F., Modern Refrigeration and Air
Conditioning, 18th
Edition, The Goodheart-Willcox Company Inc
Dossat Roy J., Horan Thomas J., Principles of Refrigeration, Fifth Edition, Prentice
Hall
Trott A. R., Welch T. C., Refrigeration & Air Conditioning, Third Edition,
Butterworth Heinemann
Whitman W. C., Johnson W. M., Tomczyk J. A., Refrigeration and Air Conditioning
Technology 5th
Edition, Thomson Delmar Learning
Refrigeration and Air Conditioning, 3rd
Edition; Air Conditioning and Refrigeration
Institute. Library Reference 621.56REFR
Videos:
History of Refrigeration; TAFE SA Cat No 88.017 9 mins (SIT No. 92)
Jobs in Air Conditioning; AMCA 11 min 29 sec (SIT No 67)
History of the Refrigerator (SIT No 75)
Heat & Pressure; TAFE SA Cat No 85.022 16 mins (SIT No A1)
Basic Refrigeration Cycle; TAFE SA Cat No 85.050 9 mins (SIT No A2)
Reciprocating Compressors: TAFE SA Cat No 86.040 7 mins (SIT NoG1)

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Content Summary:
Refrigeration Fundamentals:
1. History of Refrigeration. 6
2. Six Main Classifications of the Industry. 10
Assignment. 12
3. Matter. 13
4. Heat and Temperature. 16
5. Sensible and Latent Heat. 22
Product Storage Data. 24
Heat Load Calculations. 25
6. Pressure. 29
7. Refrigerant Conditions. 34
8. Refrigerant Relationship. 38
Pressure Temperature Charts.(Saturation Charts). 40
Practical Exercise 1. 41
9. Introduction to the Basic Vapour Compression System. 43
10. Major Components of the Vapour Compression System.
Compressors. 47
Condensers. 53
Evaporators. 59
Temperature Difference of the Condenser and Evaporator. 63
Secondary Refrigerants. 64

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Flow Controls. 65
Refrigerant Distributors. 67
Observational Exercise 1. 68
Practical Exercise 2. 69
Air Conditioning Fundamentals:
11. Introduction to Air Conditioning. 78
Types of Air Conditioning. 79
Comfort Conditions. 81
Basic Systems Layout. 84
Ventilation Systems. 86
SAA Codes. 88

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Assessment:
Grade Code: 72
GRADE CLASS MARK (%)
DISTINCTION >=83
CREDIT >=70
PASS >=50
Assessment Events: Hours
1. Assignment 18/72 10%
2. Theory Test 1 36/72 40%
3. Theory Test 2 54/72 30%
4. Theory Test 3 72/72 20%
100%
Assignment: Written report of 1000 words covering the classifications of the
six main areas of the Refrigeration and Air Conditioning
industry.
Theory Test 1: Short answer and multiple choice questions, diagrams
and calculations.
This assessment covers contents from 1 to 9 of the content
summary.
Theory Test 2: Short answer and, multiple choice questions, diagrams
and calculations.
This assessment covers contents from 10 to 11 of the content
summary.

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Refrigeration Fundamentals:
1. History of Refrigeration:
Purpose:
The purpose of this section is to provide you with an insight into the development of
refrigeration systems from the discovery of ice as a means of preserving foods
through the technological advances of modern day.
Recommended videos:
History of Refrigeration; TAFE SA Cat No 88.017 9 mins (SIT No. 92)
History of the Refrigerator (SIT No 75)
Primitive man discovered that coldness slowed down the rate of deterioration of meat
and other organic substances. It was eventually realised that this was due to the lower
ambient temperature.
Most evidence indicates that the Chinese were the first to store natural ice and snow
to cool wine and other delicacies. Evidence has been found that ice cellars were used
as early as 1000 B.C. in China. Early Greeks and Romans also used underground pits to
store ice which they covered with straw, weeds, and other materials to provide
insulation and preserve it over a long period.
Ancient people of Egypt and India cooled liquids in porous earthen jars. These jars
were set in the dry night air, and the liquids seeping through the porous walls
evaporated to provide the cooling.
Other examples of early refrigeration used in ancient times are:
In 356 B.C. Alexander the Great supplied his army with refrigerated wine by
utilising the use of natural ice.
The emperor Nero in 68 A.D. used ice to cool and control room temperature.
In the Gironde region of France a particularly cold cave was discovered which
was used as a refrigerated store around 3000 B.C.
The Roman Catacombs, originally quarries, were used as food stores.
In the 18th
and 19th
centuries, blocks of natural ice were cut from lakes and ponds in
winter and stored underground for use in the warmer months. During the 19th
century
blocks of ice were distributed for use in purpose built containers called iceboxes. At
the time, iceboxes were sufficient for the keeping of foodstuffs but towards the end of
the 19th
century new inventions were being developed for the storage of food.

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The development of mechanical refrigeration had to await progress in the physical
sciences. This included a clear concept of the nature of gases and liquids, the
relationship between heat and other forms of energy, the behaviour of vapours, etc.
The branch of physics that forms the scientific basis of modern refrigeration is
thermodynamics.
Thermodynamics is the science of the mechanics of heat.
The first law of thermodynamics:
Heat and mechanical work were equivalent and stood in a fixed relationship to
each other.
The first law of thermodynamics in refrigeration is attributed to Robert Mayer, a
German and Joule, an Englishman.
The second law of thermodynamics:
Wherever there is a temperature difference, a moving force can be generated.
The second law of thermodynamics in refrigeration is attributed to Sadi Carnot, a
Frenchman (who first introduced the term entropy) and Rudolph Clausius, a German.
Gas laws:
An understanding of the behaviour of what we call refrigerants is equally as
important. i.e. the behaviour of the gas laws can be applied to refrigerants.
Historical dates for the development of the refrigeration industry:
1662 – 1802 Boyle, Gay-Lussac, Dalton, Charles and Mariotte were credited with
formulating the Gas Laws. They showed the exact way in which
volume, pressure and temperature are connected behaviourly in ideal
gases.
1895 Richard Mollier calculated the first exact vapour tables for CO2 and
introduced a graphic representation of the properties of steam, air and
refrigerants, which still bear his name.
1823 Michael Faraday discovered that certain gases under constant pressure
will condense when they cool.
1834 Jacob Perkins filed a patent for a closed refrigeration system using
liquid expansion and then compression to produce cooling.
1848 James Harrison sets up the world’s first ice manufacturing plant in
Geelong, Victoria, and secured patents to cover his invention. His
system used ether which is dangerous due to its flammability.

1861 Ferdinand Carre, a Frenchman, developed a mechanical refrigerator
using liquid ammonia. His machine was used to make ice at a rate of
250kgs per hour.
1895 Richard Mollier introduces a graphic representation of vapour tables
for CO2, steam and refrigerants.
1902 Willis Carrier designed a humidity control to accompany a new air
cooling system. He also originated the Carrier equation upon which the
psychrometric chart and air conditioning is based.
1925 First industrial use of dry ice.
1931 Refrigerant R12 was developed by Thomas Midgely and C. f.
Kettering.
1933 The introduction of the ‘Freon’ group of refrigerants that was to
revolutionise the refrigeration and air conditioning industry.
1939 Copeland introduces the first successful semi-hermetic (Copelamatic)
field serviceable compressor.
Only a half century ago, the iceman was a regular
figure in most neighbourhoods, delivering blocks
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of ice to keep food cold.
1974 Professors Rowland and Molina presented the “ozone theory” that
CFCs were depleting the ozone layer.
1985 Stratospheric ozone hole discovered.
1987 Industrialised countries including Australia sign the Montreal Protocol
for the reduction of CFC refrigerants.
1990 London Amendments to re-evaluate the world’s production of CFC’s.
1990 Introduction of new HCFC refrigerants R123 & R134a into the
refrigeration industry.
1992 Introduction of HCFC, R404A as a replacement for R502.
1992 Copenhagen Amendments to increase the percentage of phase out of
CFC’s.
1997 Kyoto Protocol intended to reduce worldwide global warming gas
emissions. The greenhouse effect, or global warming, had become a
major environmental issue.
1998 – 2005 R410A, an efficient and environmentally friendly HFC based
refrigerant blend for residential and light commercial air conditioning
applications is used with scroll compressor for greater efficiency.
2005 The industry is now so diverse, and technologically so advanced that it
is uncommon for the modern technician to be conversant in all areas of
the industry. It has become necessary to “specialise” in one of the
many sectors whether it be installation, commissioning, or servicing. It
is to be further decided whether to perform this specialisation in the
domestic, industrial, commercial and transport area of refrigeration and
air conditioning.

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2. Six Main Classifications of the Industry:
Purpose:
The purpose of this section is to provide the underpinning knowledge and skills to
identify the various applications within the Refrigeration and Air Conditioning
Industry.
Recommended videos:
Jobs in Air Conditioning; AMCA 11 min 29 sec (SIT No 67)
The six main classifications of the industry are:
Appliance Servicing / Domestic Refrigeration
Commercial Refrigeration / Beverage Cooling and Commercial Cabinets
Industrial Refrigeration / Industrial Freezing and Equipment
Transport and Marine
Comfort Air Conditioning / Package and Central Air Conditioning Equipment
Process Air Conditioning / Industrial Air Conditioning / Specialised Air
Conditioning Equipment
Summary:
The three main areas of the industry are appliance servicing, refrigeration and
air conditioning.
The appliance industry covers domestic refrigerators and freezers, and air
conditioning systems
The refrigeration industry covers commercial and industrial applications, for
example merchandising cabinets, coolrooms, freezer rooms, icemakers,
beverage coolers etc.
The air conditioning industry covers residential installations, mechanical
services in office buildings, shopping centres and hospitals, as well as
industrial processes such as printing, textile and drug manufacturing.
Air conditioning is the simultaneous year-round control of temperature,
humidity, air purity, air movement and noise, within an enclosed space.
• For short-term storage of food, the temperature is 3o
C and the freezer
temperature -18o
C. (Domestic application).

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• Air-conditioned space for human comfort should be approximately 23o
C and
50 to 55% relative humidity (RH).

The Refrigeration & Air Conditioning Industry
Domestic Refrigeration
Appliance Servicing
Cabinets, Coldrooms
Beverage Cooling, Cold Plates
Freezer Rooms, Ice Making
Soft Serve
Commercial
Food Processing
Food Storage
Specialised Equipment
Industrial Ice making
Industrial
Fishing Boats
Containers
Trucks
Rail Cars
Transport / Marine
Refrigeration
Home A / C
Small, Medium Unit
Large Buildings
Comfort
Meat Processing Rooms
Switchrooms
Computer Rooms
Laboratories
Process
Air Conditioning
3 Main Fields of the Industry
Refrigerators
Freezers
Cabinets
Display
Freezers
Coldroom (small)
Beverage Cooling (4O
C)
Water Coolers
Temprites
Dispensers
Cold Plates
Butcher Shops
Salad Bars
Freezer Rooms (Small)
-20
O
C to –40
O
C
Ice Making
Flaked
Crushed
Cubed
Soft Serve
Ice Cream
Food Processing
Ice Creameries
Blast Freezers
Breweries
Wineries
Food Storage
Long term freezers
Specialised Equipment
Chemical manufacture
Petro / Chemical
Industrial
Ice making
Block ice
Crushed ice
Dry ice
Fishing Boats
Trawlers
Mother ships
Containers
Trucks
Rail
Ships
Trucks / Rail
Semis
Van
Refrigerated Rail Car
Planes
Boats
Trains
Buses
Car
Home A / C
Room Air Conditioner (RAC)
Split Systems
Evaporative
Large Buildings
Central Plant
Hospitals
Office Blocks
Departmental Stores
Small / Medium
Units
Homes
Small Offices
Small Shops
Meat Processing Rooms
Butcheries
Switchboards
Lift Rooms
PABX Rooms
Computer Room
Banking
Offices
Laboratories
Bacteria Growth
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Slush machines
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Assignment:
Classifications of the Refrigeration and
Air Conditioning Industry.
Purpose: This assignment is to provide you with the relevant information to
differentiate between the different areas of specialisation within the
Refrigeration and Air Conditioning Industry.
Task: Compile a written report that covers the following criteria:
Describe each of the six main classifications of the Refrigeration and
Air Conditioning Industry.
For each classification, select one type of system and report on its
construction, operation and conditions which distinguish it from other
systems. You will need to include the refrigerant type, operating
pressures and the desired operating conditions (temperature and
humidity).
Criteria: Your class teacher will advise when the assignment is to be handed in and any
penalties that may exist for late submissions.
Pictures and/or diagrams must accompany each classification.
Each classification must commence on a new page and be of approximately
200 words.
All pages are to be numbered.
The assignment must be legible; i.e. it may be hand written provided it is neat
and easily read.
The assignment is to be presented in a folder. A single plastic sleeve is not
considered a folder for presentation.
You will need to include a cover page (which includes your name, class, due
date and teachers name), a contents page (listing page numbers for each
classification) and a bibliography (last page) acknowledging all references.
Three hours of class time will be allocated for library research and study.

3. Matter:
Purpose:
The purpose of this section is to provide you with the underpinning knowledge and skills to
identify the basic structure of matter ie, atoms and molecules that are inherent in the
formation of solids, liquids and gases. To understand how ‘heat’ flows.
Matter
Matter is anything that has mass and occupies space. It can exist as a solid, liquid or vapour
(gas). The smallest particle of matter is the atom.
The Atom
The atom consists of a nucleus at its centre and is made up of protons (+ charges), neutrons
(neutral charges) and electrons (- charges) which orbit the nucleus in much the same way as
the planets orbit the sun. The electron’s orbit forms ‘shells’. The inner shells are held in
orbit tightly, while the outer shells are not held as tightly.
Molecules
All matter is composed of molecules. The molecule is the smallest stable particle of
matter into which a particular substance can be subdivided and still retain the identity
of the original substance. They are formed from the bonding of atoms into groups.
Molecules made up of only one type of atom called ELEMENTS and are pure in
nature.
Molecules made up of two or more types of atoms are called COMPOUNDS.
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The molecules in all types of matter vibrate. The rate at which they vibrate (their
KINETIC ENERGY) depends on how much heat energy is added to or removed from
the matter and how much matter exists in a body …… or it’s MASS.
In gases, the molecules are comparatively far apart and can move freely within the
space they occupy and they need to be contained, such as air in a balloon.
In liquids, the molecules are more closely crowded together; they cannot move so
freely and collide more often. Liquids are held in the shape of the space they occupy
and must be supported at the sides and bottom, such as water held in a bucket.
In solids, the molecules occupy fixed positions but still vibrate. Solids need to be
supported from the bottom only, such as a tabletop being held up (supported) by the
legs.
The force exerted by a:
Solid is downward
Liquid is downward and sideways
Gas is in all directions
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Review Questions:
1. An atom consists of:
a) Molecules, electrons and neutrons.
b) Electrons, protons and neutrons.
c) Neutrons, elements and molecules
d) Resistance, molecules and current.
2. An element is made up of:
a) Molecules and protons.
b) More than one type of atom.
c) Current flow and neutrons.
d) One type of atom only.
3. All matter is:
a) Made up of electrons only.
b) Dependent upon neutron structure.
c) Constructed of only one type of atom.
d) Occupies space and has mass.
4. All molecules:
a) Vibrate at different rates according to their state.
b) Vibrate at the same rate.
c) Do not vibrate.
d) Are made up of heat energy.
5. Identify the “charge of the following;
An electron ___________________________________________________
A neutron _____________________________________________________
A proton _____________________________________________________

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6. In what direction is force exerted on:
A solid? _______________________________________________________
A liquid? ______________________________________________________
A vapour or gas? ________________________________________________
7. Give a definition for the term, “compound”.
______________________________________________________________
______________________________________________________________

4. Heat / Temperature:
Recommended videos:
Purpose:
The purpose of this section is to provide an understanding of the characteristics of heat,
temperature, and the transfer of heat energy.
Heat:
Heat is a form of energy. Energy is the ability to do work.. Heat can be converted into other
forms of energy and other forms of energy can be converted into heat.
Heat transfer laws.
Heat can only transfer from a hot ‘body’ to a cold ‘body’. The greater the difference in heat
content between two bodies, the faster the transfer will be between them. Where there is no
heat content difference there can be no transfer.
The three methods of heat transfer are:
Conduction: by physical contact of two or more objects at
different temperatures.
Convection: by currents flowing in fluids ie. liquids and gases,
caused by differences in temperature. Warmer less
dense fluids rise whilst heavier colder fluids will fall.
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Radiation: by heat rays; electromagnetic waves through a vacuum
or gas. The most common type of radiation is the heat
received from the sun.
The main types of energy are potential and kinetic:
Potential Energy – is energy in waiting, e.g. a battery or chemical.
Kinetic Energy – energy in motion or the energy of change, e.g.
electrical to mechanical energy (an electric motor).
Other types of energy:
Mechanical – an electric motor.
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Electrical – delivered by a generator or battery.
Light – lamp/luminare or television screen.
Chemical – petrol, gun powder.
SI Units:
The SI unit for work and energy is the ‘Joule’ however; we more commonly refer to the
kilojoule (kJ) as the joule is such a small value.
Power:
Power is the rate at which work is done or energy is expended. Work over time is power,
hence joules per second equate to Watts (W) or kilowatts (kW).
Temperature Difference:
Temperature difference (td) is the difference in temperature between two separate objects
and is measured in Kelvins (K).
Temperature Change:
Temperature change (∆t) is the change in temperature that occurs when heat is added or
removed from a substance. Again, it is measured in Kelvin (K).
Temperature:
Temperature is the measure of the heat intensity or heat level of a substance. Temperature
alone does not indicate the amount of heat in a substance.
The temperature of an object is directly related to the thermal kinetic energy of its molecules.
Temperature therefore is related to heat. Temperature however does not indicate how much
heat is contained in a substance: for example, a lighted match may be hot enough to burn, but
does not contain enough heat energy to boil a kettle of water. Likewise, a pilot flame in a gas
hot water heater burns at the same temperature the main jets, but the main flame gives off
more heat than the pilot flame, thus heating the water.
Temperature Measurement:
Temperature is measured with a thermometer;
a) through uniform expansion of a liquid in a sealed glass tube. There is a bulb at the bottom
of the tube with a quantity of liquid (mercury or alcohol) inside which expands and contracts
as heat is added or removed.
b) the expansion and contraction of metal to measure temperature;
c) by measuring a small electric voltage generated in a thermocouple;
d) thermistors are the most common method of measuring temperature. A constant voltage is
applied to a component which changes its resistance if heat is applied or removed.
The temperature scale in common use today is the Celsius scale. The point at which water
freezes under standard atmospheric pressure (at sea level) is taken as the zero point, and the
point at which water boils under standard atmospheric pressure is designated at 100. The
scale is then divided into 100 equal units called degrees.

The Kelvin scale is a scale using the same divisions as the Celsius scale, but setting the zero
of the scale at the temperature at which all molecular movement in an object ceases; that is,
where no more heat exists in the body and its temperature cannot be lowered any further.
This temperature is believed to correspond to –273 degrees on the celsius scale; and is
known as absolute zero which is 273 degrees below the standard zero on the celsius scale.
The Fahrenheit scale was used in Australia prior to the introduction of the SI (metric)
system. Using this scale, water boils at 212O
F and water freezes at 32O
F.
Temperature Conversions
K = 0
C + 273
0
C = K – 273
Testing the Accuracy of a Thermometer in the Field:
We know that water freezes and ice melts at 0O
C and that water boils and steam condenses at
100O
C. Consequently, there are two methods for testing the accuracy of a thermometer in the
field.
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The first method is the freezing method. This requires placing the thermometer in a solution
of ice and water. The solution should consist of 30% water and 70% ice. In this solution the
thermometer should indicate 0O
C on the scale.
The second method is to place the thermometer into a container of boiling water. The
thermometer should indicate 100O
C.
Both of the above methods will only be accurate at sea level.
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Review Questions:
1. Heat is;
a) a measure of temperature
b) energy
c) always intense
d) energy that changes its characteristics ie, (sensible to latent). ( )
2. Heat always flows from;
a) higher electrical pressure to lower electrical pressure
b) a colder point to a hotter point
c) from a hotter point to a colder point
d) the refrigerant to the product being cooled ( )
3. Three methods of heat transfer are;
a) convection, radiation, saturation
b) radiation, conduction, subcooling
c) conduction, radiation, sublimation
d) conduction, radiation, convection ( )
4. Temperature is;
a) equivalent to heat
b) the measure of the intensity of heat
c) the energy that causes a liquid to change state
d) responsible for cooling and heating ( )
5. 0 Kelvins is equivalent to:
a) 2730
C
b) 00
C
c) – 2730
C
d) the temperature generated by rapid molecular movement ( )

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6. Give one example for each of the following methods of heat flow:
Convection ____________________________________________________
______________________________________________________________
Conduction ____________________________________________________
______________________________________________________________
Radiation ______________________________________________________
______________________________________________________________
7. List the SI unit and symbol for:
Energy __________________ Temperature measurement ___________
Power ___________________ Temperature difference ______________
8. Describe two methods for the field testing of thermometers:
______________________________________________________________
______________________________________________________________
______________________________________________________________
______________________________________________________________
______________________________________________________________
______________________________________________________________
10. Under what conditions would these field tests be considered accurate?
______________________________________________________________
______________________________________________________________

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5. Sensible & Latent Heat:
Purpose:
The purpose of this section is to provide you with the underpinning knowledge and skills to
identify the various types of heat, their measurement, and to apply ‘heat’ theory to a
refrigeration system..
Heat Measurement:
The SI unit for heat is called the joule (J). However, in refrigeration and air conditioning
systems the kilojoule (kJ), 1000 joules is used.
The amount of heat required to raise the temperature of 1kg of water by 1K is equal to
4.187kJ. Similarly, the amount of heat required to be removed to lower the temperature of
1kg of water by 1K is also 4.187kJ.
Latent Heat:
Latent heat is defined as that heat which brings about a change of state with no change in
temperature. This refers to a change from a solid to a liquid, or a liquid to a vapour ie. water
changes state to a vapour at 1000
c at sea level. If a full pot of water is boiling it will be at
1000
c. When half of the water has vapourised the water temperature will still be at 1000
c.
When only a small amount of water is left it’s boiling temperature will still be 1000
c at sea
level.
Sensible Heat:
Sensible heat is defined as that heat which causes a change in the temperature of a substance,
ie. raising the temperature of water from say 500
c to 600
c. The term sensible is applied to this
particular heat because the changes in temperature it causes can be detected with the sense of
touch and can be measured with a thermometer. Sensible heat does not cause a change of
state.
Specific Heat:
The specific heat capacity of any substance is the amount of heat that must be added or
released from one kilogram of that substance in order to change it’s temperature by one
Kelvin (K).
The sensible heat required to cause a temperature change in a substance varies with the kind
and amount of that substance. Different substances require different amounts of heat per unit
mass to effect these changes of temperature above and below freezing. This is called specific
heat.

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Specific Heat Table
Material Specific heat capacity (kJ/kg K)
Wood 1.369
Water 4.187
Ice 2.110
Mercury 0.138
Alcohol 2.575
Copper 0.397
Sulphur 0.741
Glass 0.494
Brick 0.837
Glycerine 2.411
Liquid ammonia at -15o
C (258K) 4.605
Carbon dioxide at -15o
C (258K) 2.512
R22 at -15o
C (258K) 1.088
When we refer to sensible and latent heat it infers that there are two types of heat. This is not
the case, heat is heat is heat and heat is energy. The reason that these two terms are used is to
identify that the addition or removal of heat has a different effect on a substance depending
on the amount of heat in that substance at the time eg. When the addition or removal of heat
energy merely changes the temperature of a substance we call it sensible. When the addition
or removal of heat energy causes that substance to change state we call it latent.
Latent heat of fusion is the amount of heat that must be added to change a solid to a liquid
OR the amount of heat required to be removed to change a liquid to a solid.
Example: ice to water, water to ice.
Latent heat of vapourisation is the amount of heat required to change a liquid to a vapour
(gas). This is also known as the saturation point.
Example: boiling water to steam.
Latent heat of condensation is the amount of heat required to be removed to change a
vapour (gas) to a liquid.
Example: steam to water.
Sublimation is the amount of heat required to change the state of a substance from a solid to
a vapour without passing through the liquid state, eg. Dry ice to CO2.
The heat energy required to make a substance change state is much greater than that required
to change its temperature. It requires as much heat to change 1kg of water to ice as it does to
raise the temperature of that same 1kg of water to 80o
C.

In the above diagram, identify the areas of sensible and latent heat for each state of matter
(H2O).
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Product Storage Data Sheet
O
C Storage
temperature
kJ/kg K Specific heat
Product
Quick
freeze
temp
O
C Long Short
Humidity
% RH Above
freezing
Below
freezing
kJ/kg
latent
heat
O
C
freezing
point
Resp.
kJ/kg
per day
@
storage
temp
Apples -1 – 0 3 – 6 85 – 88 3.60 1.88 281 -2.3 1.67
Bacon -2 -1 2 – 4 80 2.1 1.3 68 -3.9
Bananas 5 13 – 22 85 – 95 3.35 1.76 251 -2.2
Beans (green) 13 – 22 4 – 7 85 – 90 3.8 2.00 298 -1.3 7.85
Beef, fresh lean -25 0 – 1 7 85 3.22 1.67 233 -1.7
Butter -10 -1 – 0 4 – 7 2.68 1.42 35 -1.1
Cabbage 4 – 7 90 – 95 3.94 1.97 307 -0.4
Cheese -10 0 3 – 7 2.68 1.51 184 -8.3 5.44
Cream 0 – 4 -4 -1 3.56 1.67 209 -2.2
Eggs, fresh -23 1 3.18 1.67 233 -2.8
Fish, fresh iced -25 -1 2 – 4 3.26 1.72 235 -1
Flowers -4 2 – 4 85 – 90 0
Grapes 2 – 6 7 – 10 80 – 85 3.68 1.84 270 -3.2 0.98
Ham -1 – 0 -18 -12 80 2.85 1.59 202 -2.8
Honey -2 2 – 5 1.46 1.09 60 -1 1.65
Ice cream -30 0 7 2.93 1.88 223 -3.0
Lamb -18 -12 2 – 4 82 2.81 1.26 195 -1.7
Lettuce 0 – 1 7 90 – 95 4.02 2.01 316 -0.5 8.58
Lobster, boiled 0 2 – 4 3.39 1.76 244 -2.2
Milk -4 4 – 7 3.89 2.05 288 -0.6 1.16
Mushrooms 1 – 2 12 – 16 80 – 85 7.9 2.0 303 -1.0 9.32
Onions 0 – 2 10 – 15 70 – 75 3.81 1.93 288 -0.5 1.16
Oranges 0 10 85 – 90 3.77 1.93 288 -2.2 1.63
Peaches, fresh 0 – 1 10 85 – 90 3.77 1.93 288 -1.5 2.02
Pears, fresh 0 4 85 – 90 3.60 1.88 274 -2.0 1.60
Peas -1 – 0 4 – 7 85 – 90 3.3 1.8 247 -1.1
Plums 0 4 – 7 80 - 85 3.68 1.88 286 -2.2
Pork 0 2 – 4 85 2.85 1.26 201 -2.2
Potatoes -35 -1 7 – 15 85 – 90 3.43 1.80 258 -1.7 1.67
Poultry, dressed -23 -2 –10 0 – 2 3.31 1.55 247 -2.8
Sausage, fresh -2 -1 2 – 4 80 3.72 2.34 216 -3.3
Strawberries -25 0 – 2 0.5 – 1 80 – 85 3.85 1.97 300 -1.1 7.68
Tomatoes, ripe 0 12 – 20 85 – 90 3.98 2.01 312 -0.9 1.47
Veal -25 0.5 -1 2 – 4 2.97 1.26 212 -1.7
Vegetables, mixed -2 -1 4 – 7 90 – 95 3.77 1.88 302 -1.0 4.65
Water, ice 0 4.187 2.110 335 0

32
Calculations:
The amount of heat added to or removed from a body cannot be measured, it must be
calculated.
For the following calculations it will be necessary to refer to the Product Storage Data
sheet provided on the previous page.
Sensible heat calculations above freezing:
To calculate sensible heat it is necessary to have the following information available:
The mass (weight) of the matter
The ‘specific heat capacity’ for that matter
The temperature change of that matter.
The formula used to determine sensible heat is: Q = mc∆t
Where Q = quantity of heat in kilojoules (kJ)
m = mass in kilograms (kg)
c = specific heat capacity in kilojoules per kilogram Kelvin (kJ/kgK)
∆t = change in temperature of the mass in Kelvin (K)
Example 1:
What amount of sensible heat must be removed to reduce the temperature of 10kg of
water from 20O
C to 5O
C?
From the product storage data sheet it is determined that the specific heat capacity of
water above freezing is 4.187kJ/kgK.
The temperature difference is 20O
– 5O
= 15K
Using the formula Q = mc∆t we can determine the heat quantity as follows:
Q = 10kg x 4.187kJ/kgK x 15K
= 628.05kJ

33
Example2:
What amount of sensible heat must be removed to reduce the temperature of 50kg of
water from 45O
C to 0O
C? From the product storage data sheet it is determined that the
specific heat capacity of water above freezing is 4.187kJ/kgK.
C – 0O
C = 45K
Q = 50kg x 4.187kJ/kgK x 45K
= 9420.75kJ
The removal of this amount of heat will reduce the temperature of the water to it’s
freezing temperature at sea level but will not cause it to change state to a solid. To
cause the water to freeze further heat must be removed, that is the waters’ latent heat.
Latent heat calculations:
Latent heat calculations require the following information:
The mass (weight) of the matter
The latent heat value
The formula for calculating latent heat is: Q = mLH
Where Q = Quantity of heat in kilojoules (kJ)
m = mass in kilograms (kg)
LH = latent heat value in kilojoules per kilogram (kJ/kg)
Example:
Using the information as per example 2, and the product storage data sheet we can
calculate the latent heat quantity as follows:
From the product storage data sheet we have determined that the latent heat of water
is 335kJ/kg.
Using the formula Q = mLH we can determine the latent heat quantity.
Q = 50kg x 335kJ/kg
= 16,750kJ
Now that the water is frozen, we can if need be, further reduce the temperature of the
water to a temperature which is below it’s freezing point of 00
C.

34
To accomplish this we must once again apply the sensible heat formula as the waters’
temperature is again going to be changed.
We will now calculate the amount of heat that must be removed in order to reduce it’s
temperature from it’s frozen state at 00
C to –100
C.
Sensible heat calculations below freezing:
What amount of sensible heat must be removed to reduce the temperature of the 50kg
of water from 0O
C to -10O
C?
From the product storage data sheet it is determined that the specific heat capacity of
water below freezing is 2.11kJ/kgK.
C - -
100
C = 10K
Q = 50kg x 2.11kJ/kgK x 10K
= 1055kJ
Total heat calculations:
To now determine the total heat that must be removed from the 50kg of water in order
to change its temperature from 450
C to –
100
C we must add together the sensible heat
above freezing, the latent heat and the sensible heat below freezing.
Note: When using two, or all of these steps the quantity of heat Q becomes Q1, Q2,
and Q3.
Ie. Add all of the above to achieve a total heat quantity.
QT = Q1 + Q2 + Q3
= 9420.75 + 16,750 + 1055
= 27,225.75kJ.
To calculate the system capacity in kilowatts, the total amount of heat removed from
the product can be divided by the number of seconds needed to remove the heat.
Example:

If the amount of heat removed in the above example is required to be achieved in
sixteen hours, the system capacity would be calculated as follows:
Capacity =
Time
TotalHeat
=
sx
kJ
360016
75.225,27
= 0.473kW
Note: 3600s is the number of seconds in one hour (60 minutes x 60 seconds).
35

36
Review Questions:
1. Sensible heat is;
a) that heat which causes a change in state
b) that heat which causes a change in temperature
c) equivalent to temperature
d) is only present below 00
C ( )
2. When the temperature of water is raised from 200
C to 300
C the:
a) type of heat causing the temperature change is called latent heat
b) specific heat value of the water changes
c) water boils
d) type of heat causing the temperature change is called sensible heat
3. The refrigeration industry measures heat in:
a) joules
b) grams
c) kilograms
d) kilojoules
4. Sublimation is:
a) the changing of temperature of a substance
b) when a substance freezes
c) when a substance changes state from a solid to a gas
d) when the latent heat of condensation is removed
5. What value of specific heat is required to change the temperature of 1kg of ice
by 1K?
______________________________________________________________
6. What is meant by the following terms?
Specific heat capacity
______________________________________________________________
______________________________________________________________
Sensible heat

37
______________________________________________________________
______________________________________________________________
Latent heat
______________________________________________________________
______________________________________________________________
7. Give a definition for each of the following terms:
Sublimation ____________________________________________________
______________________________________________________________
Latent heat of fusion _____________________________________________
______________________________________________________________
Latent heat of vaporisation _________________________________________
______________________________________________________________
Latent heat of condensation ________________________________________
______________________________________________________________

6. Pressure:
Recommended videos:
Purpose:
The purpose of this section is to provide you with the underpinning knowledge and
skills required to identify the various means of measuring pressure, the effects of
altitude on pressure and how pressure is applied to cause heat to move.
Pressure:
Pressure is defined as the force exerted per unit of area, ( P = area
force
) and is expressed
in Pascals (Pa). The normal pressure of air on the human body at sea level
(atmospheric pressure) is approximately 101,300 Pascals or 101.3 kilopascals (kPa) at
sea level.
Note: 1 Pascal equals 1 Newton per square metre, i.e. 1 Pa = 1 N/m2
. A Newton is the
SI unit of force. One Newton is equal to the mass of 1 kilogram being accelerated at a
rate of 1 metre per second per second.
As the pascal is rather small, kilopascals are more commonly used. 1000 pascals
equals 1 kilopascal (kPa). Occassionally mega-pascals are used (mPa) 1,000,000
pascals equal 1 mega-pascal.
Substances always exert a pressure upon the surfaces supporting them. That is, a
refrigerator (a solid) exerts a downward pressure on its legs, if they were removed the
box would fall; a liquid always exerts a pressure on the sides and bottom of a
container, such as in a beaker containing water.
A liquid in a container maintains an increasing pressure on the sides and bottom of the
container as the depth of the liquid increases. Gases however, exert an equal pressure
at all points of a container, such as in a balloon.
There are two scales commonly used for measuring pressure in the SI system:
Gauge Scale
Absolute Scale
Gauge Scale:
Gauges used in refrigeration are calibrated to read 0kPa at atmospheric pressure, it
calls atmospheric pressure 0 kPa. This is referred to as gauge pressure and it does not
take into account atmospheric pressure which is present at all times. (kPa G).
Pressures below atmospheric are usually shown as negative kilopascals (-kPa). They
can also be shown as millimetres of mercury (mm Hg) or (microns).
38

39
Absolute Scale:
When we require the total pressure reading we add 101.3 kPa (atmospheric pressure)
frequently this figure is rounded off to 100 kPa to the gauge pressure and call this
reading the absolute pressure, i.e. gauge pressure + 100 kPa = absolute pressure,
(kPa A).
Zero on the absolute scale is at no pressure at all (a perfect vacuum). A container at
zero absolute pressure contains no gas molecules. Absolute values for temperature
and pressure are used for gas law calculations etc.
Other pressure scales that have been used are; 1. pounds per square inch (P.S.I.). This
is the scale the mechanic is referring to when he states that the head pressure is 200
P.S.I. 2. atmospheric pressure (ATM), 3. bar and kilograms per square centimetre
(kg/cm2
).
Atmospheric Pressure:
The earth is surrounded by air up to a distance of 80kms. As air has mass and is
affected by gravity it exerts a pressure or weight on the earth. This pressure is known
as atmospheric pressure and is measured as 101,325N. As this is the pressure acting
on each square metre of the earth’s surface it is measured as 101,325 Pa. OR 101.325
kPa.
This is the value of air pressure at sea level, which gives a uniform standard
throughout all the earth and is also referred to as one atmosphere which is
approximately equivalent to one bar. One bar is 100 kPa. 1000 kPa. is therefore
equivalent to 10 bar. Atmospheric pressure does not remain constant but varies with
temperature, humidity and altitude etc.
Atmospheric pressure can be measured by means of a column of mercury (Hg). The
open end of a test-tube is placed in a bowl of mercury. A complete vacuum is then
pulled on the test-tube thus there is absolutely no pressure in the tube. Because the
pressure outside the tube (atmospheric) is now greater than the pressure inside the
tube the atmospheric pressure acting on the surface of the mercury in the bowl will
force the mercury up inside the tube to a height of 760mm. This apparatus is called a
barometer.

Types of Pressure Measuring Devices:
Pressure can be measured by using the following types of instruments:
Gauges: Bourdon Tube; Pressure (measures pressure above 0 kPa G &
Compound (measures pressure above and below 0 kPa G).
Manometers & magnehelic gauge:
U tube & Inclined; used to measure pressure drop or variation
across air conditioning filters or duct pressures.
Vacuum gauges:
are used to measure very low pressure below 0 kPa G and use
the following scales:
- Microns
- Torr
- Millimetres of Mercury
- Pascals or Kilopascals
Barometers: used to measure atmospheric pressure
General Gas Laws relate to Pressure – Temperature – Volume. All gas laws are based
on “absolute” values.
Charles’ Law: Gases behave consistently with temperature changes. This is stated in
Charles’ Law. ‘At a constant pressure the volume of gas varies directly as the absolute
40

41
temperature; and at a constant volume, the pressure varies directly as the absolute
temperature.’
Boyle’s Law: This expresses a very interesting relation between the pressure and the
volume of a gas. It is stated as follows:
‘The volume of a gas varies inversely as the pressure, provided the
temperature remains constant.’
Dalton’s Law: Dalton’s Law of partial pressures is the foundation of the principal
operation of the absorption type of refrigerators. The law may be stated as follows:
• The total pressure of a mixture of gases is the sum of the partial pressures
of each of the gases in the mixture’, e.g. mix two gases and the total
pressure will equal the sum of their individual pressures.
• The total pressure of the air is the sum of the oxygen, the nitrogen, the
carbon dioxide and the water vapour pressure.
• ‘A liquid will vaporise regardless of the total pressure, provided that the
pressure of its own vapour is low enough’, i.e. water will evaporate
without boiling.

42
Review Questions:
1. What is pressure?
___________________________________________________________
___________________________________________________________
2. Air pressure at sea level is known as?
___________________________________________________________
3. How much pressure is exerted on the human body at sea level?
___________________________________________________________
4. At altitudes above sea level, what will happen to the pressure being
exerted?
___________________________________________________________
___________________________________________________________
5. List and define the two SI scales used for measuring pressure?
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
6. List four different instruments used to measure pressure.
___________________________________________________________
___________________________________________________________
___________________________________________________________

43
___________________________________________________________
7. To what do the gas laws relate:
___________________________________________________________
___________________________________________________________
8. Briefly explain each of the following gas laws:
Charles’ Law ________________________________________________
___________________________________________________________
___________________________________________________________
Boyle’s Law ________________________________________________
___________________________________________________________
___________________________________________________________
Dalton’s Law ________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________

44
7. Refrigerant Conditions:
Purpose:
identify the different states of a refrigerant within a vapour compression system and
how a refrigerant absorbs and rejects heat.
Saturated Temperature
The saturation temperature of a refrigerant is the temperature at which a liquid will
boil or a vapour will condense. It is the point at which a change of state will occur for
a liquid to change to a vapour or vapour to change state back to a liquid as when
water changes to steam or when steam changes to water.
In its saturated state the refrigerant has a relationship between pressure and
temperature, ie, for a given pressure there will be a given temperature and vise versa.
Saturated Liquid
A saturated liquid is a liquid at its boiling point for the pressure being applied to it,
and, at this point, the addition of any more heat will cause the liquid to change state to
a vapour (addition of latent heat) without a change of temperature occurring.
In an operational system, saturated liquid is present in the evaporator and the
condenser.
Saturated Vapour
A saturated vapour is a vapour at its condensing temperature for the pressure being
applied to it and if any more heat is removed it will cause the vapour to begin to
change state into a liquid (removal of latent heat). A vapour can only be saturated
when it is in contact with the parent liquid.
In an operational system, saturated vapour is present in the evaporator and the
condenser.
Superheated Vapour
A vapour at any temperature above its saturation temperature is a superheated vapour
(sensible heat causing a change in temperature).
A superheated vapour is produced if any additional heat is added to a saturated vapour
without a change of pressure occurring.
If, after vaporisation, a vapour is heated so that its temperature is raised above that of
the vaporising liquid, the vapour is said to be superheated. In order to superheat a
vapour it is necessary to separate the vapour from its parent liquid. As long as the
vapour remains in contact with the liquid it will be saturated. This is because any heat
added to a liquid vapour mixture will result in latent heat vaporising more liquid

45
without superheating the vapour present. Superheated vapour is usually found in the
end of the evaporator, in the suction line, compressor, and discharge line and at the
start of the condenser.
Before a superheated vapour can be condensed, the vapour must be de-superheated,
that is, the vapour must first be cooled to its saturation temperature, (removal of
sensible heat). Heat removed from a superheated vapour will cause the temperature of
the vapour to decrease until the saturation temperature is reached. (the temperature at
which it will begin to condense). At this point, any further removal of heat will cause
a part of the vapour to condense at the pressure being applied to it. (removal of latent
heat).
The heat being added to a vapour which causes its temperature to rise is said to be
sensible heat.
Subcooled Liquid
If, after condensing, (the removal of latent heat) a liquid is cooled so that its
temperature is now reduced below the saturation temperature for the pressure being
applied, the liquid is said to be subcooled.
In an operational system, subcooled liquid is present at the end of the condenser, in
the liquid receiver (if fitted), and in the liquid line.
It should be noted that some of the refrigerant within the liquid receiver may also be
in a saturated vapour state as the receiver is not completely filled with liquid.
Flash Gas
Flash gas is the gas resulting from the instantaneous evaporation of refrigerant in a
pressure reducing device (Refrigerant Metering Device – RMD) which cools the
remaining liquid refrigerant to the evaporation temperature. This is caused by the
reduction of the refrigerant pressure as it enters the evaporator.
Boiling Point
When we think of “boiling” we automatically think of something that is hot because
we refer to our most common experience, that of boiling water. Water however can be
made to boil at a multitude of different temperatures by varying the pressure being
applied to it. We can make it boil at 100c
or 1200c
by changing the pressure being
applied to it.
The term boiling merely refers to a liquid changing state to a vapour and this can
occur at very high temperatures or very low temperatures depending on the pressure.
This is what occurs in a refrigeration system, by varying the pressure applied to the
refrigerant we can control its boiling temperature.

46
Review Questions:
1. What is meant by the following terms?
Saturated temperature
___________________________________________________________
___________________________________________________________
___________________________________________________________
Saturated liquid
___________________________________________________________
___________________________________________________________
___________________________________________________________
Saturated vapour
___________________________________________________________
___________________________________________________________
___________________________________________________________
Superheated vapour
___________________________________________________________
___________________________________________________________
___________________________________________________________
Sub cooled liquid
___________________________________________________________
___________________________________________________________

47
2. What is the refrigerant state in the liquid receiver?
___________________________________________________________
___________________________________________________________
3. Where in the system can we find:
Superheated vapour? __________________________________________
Saturated vapour? ____________________________________________
Saturated liquid? _____________________________________________
Sub cooled liquid? ____________________________________________
4. What is the condition of the refrigerant as it leaves the RMD/flow
control?
___________________________________________________________
___________________________________________________________

48
8. Refrigerant Relationship:
Purpose:
determine the relationship between pressure and temperature, the use of a
pressure/temperature chart and how to determine the temperatures within a
refrigeration system.
Introduction
The Refrigeration and Air Conditioning Industry is made up of many different types
of systems that operate at vastly different pressures and therefore temperatures.
By using different refrigerants we can achieve these temperature ranges and still
permit each of the systems to operate within an acceptable pressure range. This occurs
because each refrigerant has a unique pressure/temperature relationship.
Pressure/Temperature Relationship
The boiling point of any liquid is governed by the amount of pressure placed upon its
surface.
If the pressure exerted on a liquid refrigerant is increased, then its boiling temperature
will also increase. If the pressure exerted on the liquid refrigerant is decreased, then
its boiling temperature will also decrease. This pressure is applied by the refrigerant
vapour that exists above the liquid in both the condenser and evaporator. If this
vapour pressure is either increased or reduced a corresponding change in temperature
will result.
By reducing this pressure to a sufficiently low value in the evaporator, it is possible to
drop the boiling temperature to a value that is cooler than the surrounding evaporator
ambient air temperature, heat will therefore flow from the warmer air to the cooler
refrigerant, cooling the air, resulting in the process known as refrigeration. If some
form of product is stored in this air heat will transfer from the warmer product to the
cooler air and then to the colder refrigerant. This is the same process used in air
conditioning.
One of the more common refrigerants used in medium temperature applications is
R134a. It has a boiling temperature of -26O
C at atmospheric pressure (101.325A) but
this will drop to -40O
C if its pressure is reduced to 50 kPa (absolute) or (-51 kPa G).
From this it follows that an R134a refrigerator, maintaining a pressure of 50kPa
(absolute) in its evaporator, will eventually reduce the temperature to -40O
C.
The temperature within a refrigerator can be controlled by altering the saturated
evaporator pressure of the refrigerant vapour by using the pumping action of the
compressor.

49
Pressure/Temperature Charts
The relationship that exists between temperature and pressure is so consistent that
tables have been created that accurately show the boiling point of the refrigerant for
any desired pressure.
Pressure/temperature charts show this saturated pressure/temperature relationship.
The term saturation is used because the temperatures in the left column are the actual
boiling and condensing temperatures for the refrigerant pressure listed. This value
varies for each type of refrigerant.
Note: There is no direct pressure/temperature relationship for a superheated
vapour or for a subcooled liquid. These charts are called saturation charts
because they only apply when a refrigerant is in its saturated condition, that is,
only in the evaporator and the condenser. In every other part of a refrigeration
system the refrigerant is in a condition other than saturated so the chart does not
apply.

50
Saturated Pressure/Temperature Chart for Common Refrigerants
R12 R134a R409a R22 R502 R408a R404a R500 R717
O
C kPa kPa kPa kPa kPa kPa kPa kPa kPa
-70 -89 -81 -74 -87 -90
-66 -85 -75 -67 -83 -87
-62 -81 -68 -57 -78 -82
-58 -76 -60 -46 -71 -76
-54 -69 -48 -34 -64 -69
-50 -62 -71 -37 -19 -23 -23 -55 -60
-46 -54 -64 -63 -22 -2 -8 -6 -44 -50
-42 -43 -55 -54 -6 16 11 15 -33 -37
-38 -32 -45 -43 10 41 34 39 -18 -22
-34 -18 -32 -31 32 70 60 66 -3 -4
-30 -1 -17 -16 63 98 89 97 16 18
-28 5 -9 -7 80 115 105 114 35 30
-26 11 0.3 2 91 132 123 133 45 46
-24 21 10 11 106 151 141 152 54 60
-22 32 20 21 126 171 161 173 65 76
-20 44 31 33 145 191 181 195 76 89
-18 56 43 44 165 214 203 219 87 105
-16 70 56 57 185 235 227 243 100 124
-14 85 69 71 207 260 251 270 118 145
-12 103 84 85 231 284 277 297 134 165
-10 116 99 100 254 313 305 326 156 190
-8 131 115 117 284 340 334 357 174 215
-6 150 133 134 310 369 364 390 193 241
-4 165 151 152 334 400 396 424 215 269
-2 184 171 172 361 435 430 460 239 299
0 207 191 192 396 470 465 496 262 328
2 224 213 214 430 508 502 537 285 362
4 248 236 237 465 547 541 579 314 397
6 270 260 262 504 586 582 623 340 433
8 292 286 287 542 620 625 669 367 473
10 323 313 314 584 668 670 716 398 513
12 344 341 342 622 718 716 766 422 555
14 372 371 372 668 767 765 819 454 605
16 402 402 404 716 810 816 873 490 654
18 432 434 437 769 860 869 929 530 704
20 465 469 471 814 910 920 989 569 755
22 497 505 507 866 967 980 1049 610 811
24 531 543 545 917 1020 1040 1119 651 868
26 571 582 585 975 1080 1100 1179 695 930
28 605 623 626 1040 1145 1170 1249 740 995
30 644 666 670 1107 1207 1240 1329 785 1065
32 683 711 715 1165 1270 1310 1399 832 1130
34 724 758 762 1230 1340 1380 1479 875 1203
36 765 807 811 1300 1410 1460 1559 925 1277
38 824 858 863 1378 1482 1530 1639 980 1369
40 860 911 920 1448 1558 1610 1729 1038 1449
42 912 966 970 1525 1644 1700 1819 1098 1543
44 962 1024 1030 1610 1725 1790 1909 1155 1630
46 1010 1063 1090 1688 1807 1880 2009 1215 1722
48 1060 1145 1150 1770 1887 1970 2109 1278 1820
50 1118 1210 1220 1855 1977 2060 2209 1348 1914
52 1172 1277 1290 1950 2070 2160 2319 1420 2005
54 1236 1347 1360 2050 2165 2270 2429 1489 2110
56 1300 1419 1430 2140 2265 2370 2549 1560 2229
58 1362 1494 1500 2245 2378 2480 2659 1635 2366
60 1428 1571 1580 2345 2475 2590 2789 1714 2515

51
Practical Exercise 1:
Task: To determine the refrigerant type within an
unlabelled/unmarked cylinder or container.
Equipment: Unlabelled/unmarked cylinder/s container/s containing
refrigerant.
Service manifold gauge set with gauge lines.
Thermometer/s.
Pressure/temperature chart.
Procedure: Connect the service manifold gauge set to the
cylinder/container and observe the pressure therein.
Measure the ambient temperature surrounding the
cylinder/container.
Referring to the pressure/temperature chart determine the
refrigerant type in the cylinder/container. This is performed by
referencing the temperature scale and then locating the pressure
corresponding to your instrument reading. You can then
determine what refrigerant is in the cylinder/container.
Example: The ambient temperature is 22O
C and pressure is 1049kPa. By
referencing the pressure/temperature chart we can determine
that the refrigerant type is R404a.
Note: this method was useful when there were limited numbers of refrigerants
available which was before the introduction of HCFCs, HCs and HFCs. As there are
now numerous refrigerants available with very similar pressure/temperature
characteristics it is recommended that any unidentified refrigerant be returned to a
supplier as the refrigerant type can no longer be accurately determined using this
method.
A risk assessment MUST be undertaken before attempting this
exercise.

52
Review Questions:
1. If the pressure exerted on the refrigerant is increased, what will happen to the
temperature of the refrigerant?
______________________________________________________________
______________________________________________________________
2. What governs the boiling temperature of any liquid?
______________________________________________________________
______________________________________________________________
3. Pressure / temperature charts display what refrigerant relationship?
______________________________________________________________
______________________________________________________________
4. Referring to the Pressure/temperature chart, what is the refrigerant
temperature if an R404a system has an operating pressure of 1429kPa?
______________________________________________________________
5. Using a pressure temperature chart determine what refrigerant is in a cylinder
if the ambient temperature around the cylinder is 32O
C and the pressure is
1165kPa.
_____________________________________________________________

53
9. Introduction to the Basic Vapour Compression System:
Purpose:
The purpose of this section is to provide you with the underpinning knowledge and
skills to identify the various components and their function within the Basic Vapour
Compression System.
Recommended video:
Basic Refrigeration Cycle; TAFE SA Cat No 85.050 9 mins (SIT No A2)
Refrigeration is the process of removing heat energy from a product or ‘substance’ by
a cooling medium and the transferring and expelling of that heat at another point in
the system.
A refrigeration system is a machine designed to move heat energy. It does this by
transferring heat from the space to be cooled to the atmosphere.
This is done by causing the refrigerant fluid in the system to change from a liquid to a
vapour and back to liquid again in a controlled way by the adding and removing of
heat.
Note: A cycle is a series of events occurring in a specific sequence which enables a
continued repetition of the sequence without interference, i.e. a cycle is one complete
unit of a series of repetition.

The basic vapour compression system consists of the following major
components, interconnecting pipe work, and a (cooling medium) refrigerant:
Compressor: compresses and ‘circulates’ refrigerant vapour.
It is known as the heart of the system and removes the superheated vapour from the
evaporator and then compresses it, raising the pressure and temperature of the vapour
so that it can be condensed back to a liquid at normal climatic conditions. The
compressed vapour then leaves the compressor and is discharged to the condenser.
Condenser: rejects heat to the atmosphere (a heat exchanger).
The purpose of the condenser is to condense the high pressure refrigerant vapour back
to a liquid for re-use in the evaporator. The condenser transfers heat from the
refrigerant to air or water so that the refrigerant can be cooled and thus allowing it to
return to its liquid state for re-use.
Liquid Receiver: a vessel designed to store liquid refrigerant.
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This is a storage tank that is designed to hold the liquid refrigerant. It is not an
essential component to the operation of the system and in fact many types of system
system do not have one.
RMD (Refrigerant Metering Device): regulates flow of refrigerant into
the evaporator.
Its purpose is to supply liquid refrigerant to the evaporator as it is required. During
operation liquid is continually boiling in the evaporator, and its job is to replace the
evaporated refrigerant as it is drawn off by the compressor.
Evaporator: absorbs heat from the medium being cooled (a heat
exchanger).
This is the component that absorbs the heat from the substance that is to be cooled. It
holds the liquid refrigerant as it boils off, changing state and absorbing heat in the
process. When we think off boiling we think of ‘HOT”, this however, is not always
the case. If we change the pressure applied to a liquid we will change its boiling point.
Remember; the definition of boiling is the ‘changing of state of a liquid to a vapour’
and this can be achieved over a vast range of temperatures. Water only boils at 1000
c
at sea level because of the air pressure (101.325kPa.) being applied to it. Change the
pressure being applied to it and its boiling temperature will change correspondingly
ie. water will boil at a temperature less than 1000
c at the top of Mt Everest simply
because the air pressure is less.
Discharge Line: connects the compressor to the condenser.
This line conducts the superheated discharge vapour from the compressor to the
condenser.
Liquid Line: connects the liquid receiver to the RMD.
This line conducts the sub-cooled liquid refrigerant from the condenser to the
metering device.
Suction Line: connects the evaporator to the compressor.
This line conducts the superheated vapour from the evaporator to the compressor
where the cycle will begin again.
Refrigerant: the ‘fluid’ used to move heat energy
This is a heat transfer medium that readily changes state from a liquid to a vapour, (by
absorbing heat), and back again by rejecting heat, and in so doing cools a space or
product. It must change state twice during the normal refrigeration cycle.

56
The High-side of the System is that part of the refrigeration system containing the
high pressure refrigerant. It can also refer to the condensing unit which consists of the
compressor, condenser and liquid receiver all mounted on the one base. The other
component that exists in the high-side is the refrigerant metering device.
The Low-side of the System is that part of the refrigeration system containing the
low pressure refrigerant. Components on this side of the system are the refrigerant
metering device, evaporator and the compressor.
As can be seen from the previous diagram the refrigerant metering device and the
compressor exist on both sides of the system.
Basic System Operation:
The basic refrigeration cycle is as follows:
The compressor increases the pressure and temperature of the refrigerant
vapour to a high temperature high pressure superheated vapour.
The “superheated” refrigerant vapour then passes via the discharge line into
the condenser. As the refrigerant vapour ‘cools’ (rejects heat energy to the
atmosphere) it de-superheats first, when it cools to its saturation temperaure it
will begin to condense and is said to be a “saturated liquid vapour mix” and as
it continues to cool it will become 100% liquid. As it further travels through
the condenser giving up more heat its temperature will continue to drop to a
temperature that is lower than its saturation temperature, thus it is now a high
pressure, medium temperature “subcooled “ liquid.
This “subcooled” high pressure; meduim temperature liquid then passes
through the liquid receiver and via the liquid line to the RMD (refrigerant
metering device).
As the liquid passes through the RMD (refrigerant metering device) it
becomes a low pressure, low temperature liquid vapour mix which then flows
into the evaporator. This vapour is called flash gas.
The low pressure, low temperature liquid passes through the evaporator
absorbing heat from the surrounding atmosphere/product and continues to
change state at a low pressure and low temperature. At this point it is still a
liquid vapour mix at saturation temperature. Once all the liquid refrigerant has
vapourised (by absorbing latent heat) its temperature will begin to rise as even
in its vapour state it will absorb heat. Now it is warmer than its saturation
temperature, thus it has become a superheated vapour (still at low temperature
and pressure). It will then leave the evaporator and return to the compressor.
The compressor’s pumping capacity will determine the saturated suction
temperature, SST.

57
The refrigerant having returned to the compressor then enables the “vapour
compression cycle” to begin again. In effect the vapour compression system is
an example of recycling.

Review Questions:
1. List the 5 major components of a basic vapour compression system as per the
above diagram
1______________________________________________________________
2______________________________________________________________
3______________________________________________________________
4______________________________________________________________
5______________________________________________________________
2. State the purpose of each of the components that have been identified in Q1.
1______________________________________________________________
_______________________________________________________________
_______________________________________________________________
2______________________________________________________________
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59
_______________________________________________________________
_______________________________________________________________
3______________________________________________________________
_______________________________________________________________
_______________________________________________________________
4______________________________________________________________
_______________________________________________________________
_______________________________________________________________
5______________________________________________________________
_______________________________________________________________
_______________________________________________________________
3. State the name of each of the refrigerant pipes as per the diagram above.
1______________________________________________________________
2______________________________________________________________
3______________________________________________________________
4. State the function of each of these refrigeration pipes.
1______________________________________________________________
2______________________________________________________________
3______________________________________________________________

60

Refrigeration fundamental

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