The ppt contains detailed study of refrigerants used in refrigeration and air conditioning system with description. It is well formed as per the syllabus of GTU.

1. Refrigerants
used in
Refrigeration System
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Faculty Name: Prof. Ajaypalsinh G. Barad
Branch: Mechanical
Semester: 6th
Name of Subject: Refrigeration and Air Conditioning

2. Outline
• Introduction
• Classification
• Designation of refrigerants
• Properties
• Secondary refrigerants
• Future industrial refrigerants
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3. Introduction:
• The working agent in a refrigerating system that
absorbs, carries or releases heat from the place to be
cooled or refrigerated can be termed as a refrigerant.
• This heat transfer generally takes place through a
phase change of the refrigerant.
• “Refrigerant is the fluid used for heat transfer in a
refrigerating system that absorbs heat during
evaporation from the region of low temperature and
pressure, and releases heat during condensation at a
region of higher temperature and pressure.
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4. Classification of Refrigerants:
Primary Refrigerants: can be directly used for the
purpose of refrigeration.
• If the refrigerant is allowed to flow freely into the
space to be refrigerated and there is no danger of
possible harm to human beings, then primary
refrigerants are used.
• The refrigerants used in home refrigerators like
Freon-12 are primary refrigerants.
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5. Classification of Refrigerants:
Secondary Refrigerant: there may be certain situations in
which we cannot allow the refrigerant to come in direct
contact with the items being refrigerated, and then the
refrigerant used is termed as a secondary refrigerant.
• Toxic refrigerant can not be used for air conditioning in
residential buildings.
• Some refrigerants which are highly inflammable and so
their direct use is forbidden for safety reasons.
• In cooling a big cold storage, the amount of refrigerant
required may be so large that its cost becomes
prohibitively high.
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6. Designation of Refrigerants:
• The American Society of Refrigerating Engineers
(ASRE) has developed certain conventions for use in
naming different types of refrigerants.
• Thus, we have separate series for halogenated
refrigerants and other types.
• These are represented by a three digit nomenclature.
Here, the first digit represents the number of carbon
atoms in the compound minus one, the second digit
stands for the number of hydrogen atoms plus one while
the third digit stands for the number of fluorine atoms.
The remaining atoms are chlorine.
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7. Designation of Refrigerants:
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8. Designation of Refrigerants:
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9. Types of Refrigerant:
Halocarbon Compounds
• This groups of refrigerants was invented and developed by
Charles Kettering and Dr. Thomas Migely in 1928.
• These refrigerants are sold in the market under trade names
as Freon, Genetron, isotron and Arcton.
• It includes refrigerants which contain one or more of three
halogens, Chlorine, Fluorine and Bromine.
• The most of the refrigerants used for domestic,
commercial and industrial purposes are selected from this
group due to their outstanding advantages over the
refrigerants from other groups.
• The list of the halocarbon-refrigerants commonly used is
given below with their number and chemical formula.
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10. Types of Refrigerant:
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11. Types of Refrigerant:
Azetropes
• The refrigerants under this group consist of mixtures
of different refrigerants which do not separate into
their components with the changes in pressure or
temperature or both.
• They have fixed thermo-dynamic properties.
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12. Types of Refrigerant:
Hydro-carbons.
• Most of the organic compounds are considered as
refrigerant under this group.
• Many hydrocarbons are successfully used as refrigerants
in industrial and commercial installations.
• Most of them posses satisfactory thermodynamic
properties but are highly flammable.
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13. Types of Refrigerant:
Inorganic Compounds:
• The refrigerants under this group were universally used for
all purposes before the introduction of halocarbon group.
• They are still used for different purposes due to their
inherent thermodynamic and physical properties.
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14. Desirable Properties of an Ideal Refrigerant:
• Thermodynamic properties.
• Safe working properties.
• Physical properties.
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15. Desirable Properties of an Ideal Refrigerant:
Thermodynamic properties:
• Boiling Point
• Freezing Point
• Evaporator and Condenser Pressure
• Latent Heat of Refrigerant
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16. Desirable Properties of an Ideal Refrigerant:
Safe Working Properties:
• It should be chemically inert.
• It should be non-flammable, non-explosive and non-toxic
in pure state and when mixed with air in any proportion.
• It should not react with lubricating oil and with the
materials used in construction of refrigeration system.
• It should not have any effect on the stored material when
the leak develops in the system
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17. Desirable Properties of an Ideal Refrigerant:
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18. Desirable Properties of an Ideal Refrigerant:
Physical Properties:
• Specific Volume
• Specific heat of liquid and vapor
• Thermal Conductivity
• Viscosity
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19. SECONDARY REFRIGERANTS:
• The commonly used secondary refrigerants are water,
sodium-chloride brine, calcium chloride brine and
propylene glycol.
Water: When the required temperature to be maintained is
above the freezing point of water, then water is universally
used as secondary refrigerant mostly in air-conditioning
plants and industrial cooling installations.
Brines: When the temperatures required to be maintained are
below the freezing point of water then the water cannot be
used, in such case brine solutions are used.
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20. SECONDARY REFRIGERANTS:
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21. SECONDARY REFRIGERANTS:
• When the temperature requirements of the different parts in
a large building are varied, then these different temperatures
can be easily maintained by controlling the amount of brine
flowing to the part.
• Another advantage is easy to handle and easy to control
compared with primary refrigerant.
• The use of brines is advisable in order to keep coils and
pipes containing a toxic refrigerant away from the load
places.
• The secondary refrigerant also eliminates long refrigerant
lines in a system using a non-toxic refrigerant.
• The secondary refrigerant also eliminates possibilities of
leakage.
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22. Future Industrial Refrigerants:
• Chloro Fluoro Carbon (CFC) refrigerants
• Hydro Chloro Fluoro Carbon (HCFC) refrigerants
• Hydro Fluoro Carbon (HFC) refrigerants
• Hydro Carbon (HC) refrigerants
• After the finding that CFCs, and to a lesser extent HCFCs
deplete the ozone layer, over 100 countries adopted
Montreal Protocal (MP) of 1987 to phase out CFCs in the
year 2000, and HCFCs by the year 2030.
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23. Replacement for R-12 (Dichlorodifluoromethane)
• R134a (Tetra Fluoro Ethane (CF3CH2F)).
• Its boiling point is - 26.15°C which is quite close to the
boiling point of R-12 which is - 29°C at atmospheric
pressure.
• Since the refrigerant R-134a has no chlorine atom, therefore
this refrigerant has zero ozone depleting potential and has
74% less global warming potential as compared to R-12.
Future Industrial Refrigerants:
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24. Replacement for R-11 (Trichlorofluoromethane)
R-123 (Dichloro-Trifluoro Ethane (CF3CHCI2)).
• It has about 4.3°C higher boiling point than R-11.
• It is, therefore, a lower pressure replacement for R-11, thus,
having larger specific volume of suction vapor.
• Hence, its use results in 10 to 15% reduction in capacity, if
used in existing R-11 centrifugal compressors.
R-134a.
• But since boiling point of R-134a (-26.1°C) is very low
compared to boiling point of R-11 (+23.71 °C) at
atmospheric pressure, it is a much higher pressure
refrigerant and it has very much smaller specific volumes of
suction vapor.
Future Industrial Refrigerants:
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25. Replacement for R-22 (Chlorodifluoromethane)
• It is currently the most favored refrigerant in package units
and chillers. 70% of commercial refrigeration systems still
use R-22.
• The mixture (50/50 % by weight) of R-32 and R-125, is in
race for substitute of R-22.
• The mixture of (23/25/52 % by weight) of R-32, R-125, and
R-134a , is a possible substitute for R-22 with very good
capacity and energy efficiency.
Future Industrial Refrigerants:
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