Applications of Refrigeration & Air Conditioning

1. Sana’a University
Dr. Abduljalil Al-Abidi HVAC
Mechanical Engineering department
Applications of Refrigeration & Air Conditioning

2. Sana’a University
Dr. Abduljalil Al-Abidi HVAC
Mechanical Engineering department

3. Sana’a University
Dr. Abduljalil Al-Abidi HVAC
Mechanical Engineering department
The major applications of refrigeration can be grouped into
following four major equally important areas.
1. Food processing, preservation and distribution
2. Chemical and process industries
3. Special Applications
4. Comfort air-conditioning

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Dr. Abduljalil Al-Abidi HVAC
Mechanical Engineering department
1-2 Application of refrigeration in Food processing, preservation and
distribution
Storage of Raw
Fruits and
Vegetables

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Dr. Abduljalil Al-Abidi HVAC
Mechanical Engineering department
Applications Temperature
Fish Cleaning processing and freezing
Meat and poultry: -25
Dairy Products 10 to 15ºC, 4 – 5 ºC
–30 to –25oC
Beverages: 8 to12C
. Candy 5-10oC
Processing and distribution of
frozen food
–25 to -20

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Dr. Abduljalil Al-Abidi HVAC
Mechanical Engineering department

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Dr. Abduljalil Al-Abidi HVAC
Mechanical Engineering department
Applications Temperature
Separation of gases: –150oC
Condensation of Gases –10 to 10oC
Dehumidification of Air 10 to 15ºC
Solidification of Solute (Wax) below –25oC.
Storage as liquid at low pressure Natural gas 0.7
bar
–130oC.
Removal of Heat of Reaction
Cooling for preservation
Recovery of Solvents
Applications of refrigeration in chemical and process industries

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Dr. Abduljalil Al-Abidi HVAC
Mechanical Engineering department
Temperature
Cold Treatment of Metals – 90oC
Medical –10oC
Ice Skating Rinks 10 to 15ºC
Construction (exothermic process)
Desalination of Water:
Ice Manufacture
Cooling for preservation:
Recovery of Solvents
Special applications of refrigeration

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Dr. Abduljalil Al-Abidi HVAC
Mechanical Engineering department
Temperature
Laboratories Temp. Relative Humidity , Air quality
Printing Temp. Relative Humidity
Manufacture of Precision
Parts
Textile Industry Temp. Relative Humidity
Pharmaceutical Industries Temp. Relative Humidity , Air quality
Photographic Material
Farm Animals
Computer Rooms Temp. Relative Humidity , Air quality
Industrial Air conditioning

10. Sana’a University
Dr. Abduljalil Al-Abidi HVAC
Mechanical Engineering department
Refrigerants
In general, refrigerants are well known as the fluids
absorbing heat during evaporation. These refrigerants, which
provide a cooling effect during the phase change from liquid
to vapor, are commonly used in refrigeration, air
conditioning, and heat pump systems, as well as process
systems.
1. The first designers of refrigeration machines, Jacob
Perkins in 1834, and others later in the nineteenth century,
used ethyl ether (R-610) as the first commercial
refrigerant
2. In the early 1930s, the introduction of hlorofluorocarbons
(CFCs)

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Dr. Abduljalil Al-Abidi HVAC
Mechanical Engineering department

12. Sana’a University
Dr. Abduljalil Al-Abidi HVAC
Mechanical Engineering department
2.2 Classification of Refrigerants:
This section is focused only on the primary
refrigerants. which can be classified into
the following five main groups:
1. Halocarbons,
2. Hydrocarbons (HCs).
3. Inorganic compounds.
4. Azeotropic mixtures,
5. Non-azeotropic mixtures.

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Dr. Abduljalil Al-Abidi HVAC
Mechanical Engineering department
3.2.1 Halocarbons CFCs
The halocarbons contain one or more of the three halogens – chlorine,
fluorine, or bromine – and are widely used in refrigeration and air-
conditioning systems as refrigerants. These are more commonly known
by their trade names, such as Freon, Arcton, Genetron, Isotron, and
Uron. hlorofluorocarbons, In this group, the halocarbons, consisting of
chlorine, fluorine, and carbon, were the most commonly used
refrigerants R-11, R-12, R-22, R-113, and R-114
odorless, nontoxic, and heavier than air, as well as dangerous if not
handled properly
• ozone layer depletion
• greenhouse effect

14. Halocarbon Refrigerants
• Halocarbon Refrigerant are all synthetically
produced and were developed as the Freon
family of refrigerants.
Examples :
– CFC’s : R11, R12, R113, R114, R115
– HCFC’s : R22, R123
– HFC’s : R134a, R404a, R407C, R410a

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Dr. Abduljalil Al-Abidi HVAC
Mechanical Engineering department
3.2.2 Hydrocarbons HCs
HCs are the compounds that mainly consist of carbon and hydrogen.
HCs include. methane (R-50), ethane (R-170), propane
(R-290), n-butane (R-600), and isobutane (R-600a
• highly flammable
• low toxicity
• Not expensive to produce
Famlies A -Hydrobromofluorocarbons (HBFCs)
B- HCFCs
C- Hydrofluorocarbons (HFCs)
• zero ozone depletion potential (ODP),
• very low global warming potential

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Dr. Abduljalil Al-Abidi HVAC
Mechanical Engineering department
3.2.3 Inorganic Compounds
In spite of the early invention of many inorganic compounds,
today they are still used in many refrigeration, air
conditioning, and heat pump applications as refrigerants.
Ammonia (NH3)
Water (H2O)
Air (0.21O2 + 0.78N2 + 0.01Ar)
Carbon dioxide (CO2)

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Dr. Abduljalil Al-Abidi HVAC
Mechanical Engineering department
3.2.4 Azeotropic Mixtures
An azeotropic refrigerant mixture consists of two substances having
different properties but behaving as a single substance. The two
substances cannot be separated by distillation. The most common
azeotropic refrigerant is R-502, which contains 48.8% R-22 and 51.2%
R-115.
R-500 : 73.8% R12 and 26.2% R152
R-502 : 48.8% R22 and 51.2% R115
R-503 : 40.1% R23 and 59.9% R13

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Dr. Abduljalil Al-Abidi HVAC
Mechanical Engineering department
Zeotropic Refrigerants
• A zeotropic mixture is one whose composition in
liquid phase differs to that in vapour phase.
Zeotropic refrigerants therefore do not boil at
constant temperatures unlike azeotropic refrigerants.
• Examples :R404a : R125/143a/134a (44%,52%,4%)
R407c : R32/125/134a (23%, 25%, 52%)
R410a : R32/125 (50%, 50%)
R413a : R600a/218/134a (3%, 9%, 88%)

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Dr. Abduljalil Al-Abidi HVAC
Mechanical Engineering department
Prefixes

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Dr. Abduljalil Al-Abidi HVAC
Mechanical Engineering department
Refrigerants coding

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Dr. Abduljalil Al-Abidi HVAC
Mechanical Engineering department

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Dr. Abduljalil Al-Abidi HVAC
Mechanical Engineering department

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Dr. Abduljalil Al-Abidi HVAC
Mechanical Engineering department
1. Secondary Refrigerants
Secondary refrigerants play a role in carrying heat from an object or a space being cooled to
the primary refrigerant or the evaporator of a refrigeration system. During this process, the
secondary refrigerant has no phase change. In the past, the most common secondary
refrigerants were brines, which are water–salt (e.g., sodium chloride and calcium chloride)
solutions, and even today they are still used in spite of their corrosive effects. Also, the
antifreezes, which are solutions of water and ethylene glycol, propylene glycol, or calcium
chloride, are widely used as secondary refrigerants.
Second refrigerant properties
 satisfactory thermal and physical properties,
 stability,
 noncorrosiveness,
 nontoxicity,
 low cost, and
 Usability.


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Dr. Abduljalil Al-Abidi HVAC
Mechanical Engineering department

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Dr. Abduljalil Al-Abidi HVAC
Mechanical Engineering department
1. Refrigerant–Absorbent Combinations
The refrigerant–absorbent combinations (so-called working fluids) are basically used in
absorption refrigeration and heat pump systems. Inorganic and organic groups are major
sources of the refrigerants and absorbents. Some organic groups for refrigerants are amines,
alcohols, halogens, and HCs, and for absorbents, alcohols, ethers, alcohol-ethers, amides,
amines, amine-alcohols, esters, ketones, acids, or aldehydes can be used. Two well-known
examples are ammonia–water and water–lithium bromide. In some literature, the absorbent
is also called the solvent. The absorbent should have a greater chemical affinity for the
refrigerant than that indicated by the ordinary law of solubility.

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Dr. Abduljalil Al-Abidi HVAC
Mechanical Engineering department
Stratospheric Ozone Layer

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Dr. Abduljalil Al-Abidi HVAC
Mechanical Engineering department
wavelength of light

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Dr. Abduljalil Al-Abidi HVAC
Mechanical Engineering department
wavelength of light

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Dr. Abduljalil Al-Abidi HVAC
Mechanical Engineering department
UV radiation is a portion of the electromagnetic spectrum with
wavelengths shorter than visible light.
 UVA. (320–400) nm, not absorbed by ozone.
 UVB. (280–320) nm , damaging DNA, melanoma and other types of
skin cancer. Damage to some materials, crops, and marine
organisms.
The ozone layer protects the earth against most UVB coming from the
sun. Wearing hats, sunglasses, and sunscreen. However, these
precautions will become more important as ozone depletion worsens.
 UVC. shorter than 280 nm. Despite being extremely dangerous, it is
completely absorbed by ozone and normal oxygen (O2).

30. Sana’a University
Dr. Abduljalil Al-Abidi HVAC
Mechanical Engineering department
Ozone is a gas composed of three atoms of oxygen, known as a bluish gas that is harmful to
breathe. Nearly 90% of the earth’s ozone is situated in the stratosphere and is referred to as
the ozone layer. Ozone absorbs a band of UVB that is particularly harmful to living
organisms. The ozone layer prevents most UVB from reaching the ground.

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Dr. Abduljalil Al-Abidi HVAC
Mechanical Engineering department
Stratospheric Ozone Layer Depletion

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Dr. Abduljalil Al-Abidi HVAC
Mechanical Engineering department
Greenhouse Effect (Global Warming)

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Dr. Abduljalil Al-Abidi HVAC
Mechanical Engineering department
The global warming potential (GWP) of a gas may be defined as an index
comparing the climate impact of its emission to that of emitting the same
amount of carbon dioxide. The integrated effect over a fixed time allows for
time decay of the substance. A time horizon of 100 years is usually adopted,
although this is much less than the lifetime of CO2 in the atmosphere. The
refrigerant only affects global warming if released into the atmosphere
The GWP values for HFC refrigerants can be seen in Table 3.1 , for example,
R134a has a GWP of 1300, which means that the emission of 1 kg of
R134a is equivalent to 1300 kg of CO2 .
The choice of refrigerant affects the lifetime warming impact of a system and the term
total equivalent warming impact (TEWI) is used to describe the overall impact.
It includes the effects of refrigerant leakage, refrigerant recovery losses and energy
consumption. TEWI should be calculated when comparing system design options for
specific applications. Comprehensive method details with calculation examples are
given in the Guidelines. Figures 3.3 and 3.4 show the equation used and an example
for a medium temperature R134a installation.

34. Sana’a University
Dr. Abduljalil Al-Abidi HVAC
Mechanical Engineering department
The TEWI Factor
– The Total Equivalent Warming Impact (TEWI)
rating measures the efficiency of a refrigerant by
combining its direct and indirect global warming
contribution.
– It is expressed in kg of CO2.
• TEWI = leakage rate + Recuperation Rate + Indirect
emissions due to energy consumption

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Dr. Abduljalil Al-Abidi HVAC
Mechanical Engineering department
Figure Method for calculation of TEWI values

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Dr. Abduljalil Al-Abidi HVAC
Mechanical Engineering department
Leakage Rate
• Leakage rate is the amount of green house gases released into
the atmosphere by the refrigeration system. It is given by the
mass of refrigerant emissions in kilograms times the GWP of
the refrigerant
• Leakage Rate = Mass of refrigerant leaking from system x
GWP of Refrigerant
• Typical leakage rates:
Hermetic compressor : 1 - 2%
Split units : 6 - 8%
Automotive air conditioning : 10 - 20%

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Dr. Abduljalil Al-Abidi HVAC
Mechanical Engineering department
Recuperation Rate
• Recuperation rate = GWPref x Chargeref x
( 1 – recuperation factor )
Recuperation factor is the percentage of refrigerant recovered
when a refrigeration or air conditioning equipment reaches
the end of its useful life.

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Dr. Abduljalil Al-Abidi HVAC
Mechanical Engineering department
Indirect Emissions
Indirect emissions are emissions of CO2 which occur by
generation of electricity needed to run the RAC
equipment during its lifetime.
CO2 contrib = Machine life x Energy cons. Pa x Emission factor
The emission factor is the amount of CO2 released into the atmosphere
when fuel is burned to produce one kWh of electricity. The emission factor
for electricity varies from country to country and according to the primary
source of energy.

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Dr. Abduljalil Al-Abidi HVAC
Mechanical Engineering department
Figure Comparison of TEWI values, data corresponds to the effect of increased
refrigerant charge and increased power consumption

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Dr. Abduljalil Al-Abidi HVAC
Mechanical Engineering department
Example of TEWI Calculation
• Chiller unit running on R407c with a charge of 426 kg.
• Average leakage rate pa : 4 kg
• Lifespan of equipment : 25 years
• GWP of R407c : 1610 kg CO2
• Average power rating of unit : 298.3 kW
• Chiller working on an average of 20 hours per day
• Recuperation factor assumed to be 50 %

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Dr. Abduljalil Al-Abidi HVAC
Mechanical Engineering department
Calculation of TEWI
• Leakage Rate = 4 x 1610 x 25 = 128 800 kg CO2
• Recuperation rate = 1610 x 426 x (1 – 0.5) = 342 930 kg CO2
• Indirect contribution due to energy consumption =
= 25 x (298.3 x 20 x 365) x 0.6 = 32 663 850 kg CO2
{Emission factor is assumed to be 0.9 for Mauritius}
TEWI factor for the chiller unit calculated over its lifetime of 25 years :
128 800 + 342 930 + 32 663 850 = 33 135 580 kg CO2
This implies that the chiller will contribute to the equivalent of 33 135 580 kg of CO2
over its useful life of 25 years.
• Direct emissions = 1.4 % of the indirect emissions

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Dr. Abduljalil Al-Abidi HVAC
Mechanical Engineering department
Improving TEWI of a System
• Using refrigerant with lower GWP
• Eliminating leakages in the system
• Improving the electrical efficiency of the
system

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Dr. Abduljalil Al-Abidi HVAC
Mechanical Engineering department
1. Alternative Refrigerants
New, alternative substances are required to replace the fully halogenated refrigerants
that are believed to contribute to atmospheric ozone depletion. In the past decade,
many research and development studies on the synthesis and characterization of
alternative refrigerants were undertaken. The replacement of restricted ODSs by any
alternative may involve substantial

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Mechanical Engineering department
IDEAL PROPERTIES FOR A REFRIGERANT
These can be listed as
● High latent heat of vaporization
● High suction gas density
● Positive but not excessive pressures at evaporating and condensing
conditions
● Critical temperature and triple point well outside the working range
● Chemically stable, compatible with construction materials and
miscible with lubricants
● Non-corrosive, non-toxic and non-flammable
● High dielectric strength
● Environmentally friendly
● Low cost
Needless to say, no single fluid has all these properties, and the choice
of fluid for any particular application will always be a compromise

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Dr. Abduljalil Al-Abidi HVAC
Mechanical Engineering department

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Mechanical Engineering department

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Flammability
• Approximate auto ignition temperatures
• R22 630 ºC
• R12 750 ºC
• R134a 740 ºC
• R290 465 ºC
• R600a 470 ºC
• Oil 222 ºC

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Dr. Abduljalil Al-Abidi HVAC
Mechanical Engineering department

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Dr. Abduljalil Al-Abidi HVAC
Mechanical Engineering department
Subcooling
Condensed liquid refrigerant is usually subcooled to a temperature lower than the
saturated temperature corresponding to the condensing pressure of the refrigerant,
shown in Fig. 9.6a as point 3. This is done to increase the refrigerating effect, The
degree of subcooling depends mainly on the temperature of the coolant (e.g.,
atmospheric air, surface water, or well water) during condensation, and the construction
and capacity of the condenser.
Superheating
As mentioned before, the purpose of
superheating is to avoid compressor
slugging damage. Superheating
is shown in Fig. 9.6b. The degree of
superheat depends mainly on the type of
refrigerant
feed and compressor as well as the
construction of the evaporator

53. Sana’a University
Dr. Abduljalil Al-Abidi HVAC
Mechanical Engineering department
Example 9.1. A 500-ton (1760-kW) single-stage centrifugal vapor compression
system uses
HCFC-22 as refrigerant. The vapor refrigerant enters the compressor at dry
saturated state. The
compression process is assumed to be isentropic. Hot gas is discharged to the
condenser and
condensed at a temperature of 95°F (35°C). The saturated liquid refrigerant then
flows through a
throttling device and evaporates at a temperature of 35°F (1.7°C). Calculate:
1. The refrigeration effect
2. The work input to the compressor
3. The coefficient of performance of this refrigeration cycle
4. The mass flow rate of the refrigerant

54. Sana’a University
Dr. Abduljalil Al-Abidi HVAC
Mechanical Engineering department
MULTISTAGE VAPOR COMPRESSION SYSTEMS
When a refrigeration system uses more than single-stage compression process, it is
called a multistage system (as shown in Fig. 9.7), and may include the following:
1. A high-stage compressor and a low-stage compressor
2. Several compressors connected in series
3. Two or more impellers connected internally in series and driven by the same motor
or prime mover, as shown in Fig. 9.7
4. A combination of two separate refrigeration systems
The discharge pressure of the low-stage compressor, which is equal to the suction
pressure of the
high-stage compressor, is called the interstage pressure. The reasons for using a
multistage vapor compression system instead of a single-stage system
are as follows:
1. The compression ratio Rcom of each stage in a multistage system is smaller than that
in a single stage unit, so compressor efficiency is increased. Compression ratio Rcom is
defined as the ratio of the compressor’s discharge pressure pdis, psia (kPa abs.), to
the suction pressure at the compressor’s inlet psuc, psia (kPa abs.), or

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Dr. Abduljalil Al-Abidi HVAC
Mechanical Engineering department
2. Liquid refrigerant enters the evaporator at a lower enthalpy and increases the
refrigeration effect.
3. Discharge gas from the low-stage compressor can be desuperheated at the
interstage pressure.
This results in a lower discharge temperature from the high-stage compressor
than would be
produced by a single-stage system at the same pressure differential between
condensing and
evaporating pressures.
4. Two or three compressors in a multistage system provide much greater
flexibility to accommodate
the variation of refrigeration loads at various evaporating temperatures during
part-load operation.
The drawbacks of the multistage system are higher initial cost and a more
complicated system
than that for a single-stage system.