Refrigerants

used in

Refrigeration System

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Faculty Name: Prof. Ajaypalsinh G. BaradBranch: MechanicalSemester: 6th

Name of Subject: Refrigeration and Air Conditioning

Outline

• Introduction

• Classification

• Designation of refrigerants

• Properties

• Secondary refrigerants

• Future industrial refrigerants

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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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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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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.5

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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Designation of Refrigerants:

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Designation of Refrigerants:

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Types of Refrigerant:

Halocarbon Compounds

• This groups of refrigerants was invented and developed byCharles Kettering and Dr. Thomas Migely in 1928.

• These refrigerants are sold in the market under trade namesas Freon, Genetron, isotron and Arcton.

• It includes refrigerants which contain one or more of threehalogens, Chlorine, Fluorine and Bromine.

• The most of the refrigerants used for domestic,commercial and industrial purposes are selected from thisgroup due to their outstanding advantages over therefrigerants from other groups.

• The list of the halocarbon-refrigerants commonly used isgiven below with their number and chemical formula.

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Types of Refrigerant:

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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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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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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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Desirable Properties of an Ideal Refrigerant:

• Thermodynamic properties.

• Safe working properties.

• Physical properties.

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Desirable Properties of an Ideal Refrigerant:

Thermodynamic properties:

• Boiling Point

• Freezing Point

• Evaporator and Condenser Pressure

• Latent Heat of Refrigerant

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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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Desirable Properties of an Ideal Refrigerant:

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Desirable Properties of an Ideal Refrigerant:

Physical Properties:

• Specific Volume

• Specific heat of liquid and vapor

• Thermal Conductivity

• Viscosity

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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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SECONDARY REFRIGERANTS:

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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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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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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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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, ifused in existing R-11 centrifugal compressors.

R-134a.

• But since boiling point of R-134a (-26.1°C) is very lowcompared to boiling point of R-11 (+23.71 °C) atatmospheric pressure, it is a much higher pressurerefrigerant and it has very much smaller specific volumes ofsuction vapor.

Future Industrial Refrigerants:

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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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