Refrigeration and Air Conditioning

NME:604Unit3

Presented byMr Naphis AhmadAssistant professorJETGI Barabanki

jahangirabad institute of technology

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Simple vapour absorption system

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Simple vapour absorption system In this system an absorber, a pump, a generator and a pressure reducing

valve replace the compressor.The low pressure ammonia vapour leaving the evaporator enters the

absorber where it is absorbed by the cold water in the absorber.The water has the ability to absorb the large quantity of ammonia vapour. Heat is removed in the absorber to increase the absorption capacity of

water.The strong solution in the absorber is pumped to the generator.The strong solution is heated in the generator during the heating the

ammonia vapours are driven off the solution and the weak solution flows back to the absorber.

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Practical vapour absorption system

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Practical vapour absorption systemThe simple vapour absorption system discussed previously is not

very economical. To improve the effectiveness it is fitted with the accessories an

analyzer, a rectifier and two heat exchangers.

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Ammonia Hydrogen (Electrolux) Refrigeration system

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Electrolux Refrigeration system

This type of refrigerator is also called three fluid absorption system

The main purpose of this system is to eliminate the pump so that in the

absence of moving part the machine becomes noiseless.

The three fluids used are ammonia, water and hydrogen.

The ammonia act as the refrigerant.

The hydrogen being the lightest gas is used to increase the rate of

evaporation of the liquid ammonia passing through the evaporator.

Water acts as the solvent.

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Lithium Bromide Absorption system

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Working of Lithium bromide In a water-lithium bromide vapor absorption refrigeration system, water is

used as the refrigerant while lithium bromide (Li Br) is used as the absorbent.

In the absorber, the lithium bromide absorbs the water refrigerant, creating a

solution of water and lithium bromide. This solution is pumped by the pump

to the generator where the solution is heated. The water refrigerant gets

vaporized and moves to the condenser where it is cooled while the lithium

bromide flows back to the absorber where it further absorbs water coming

from the evaporator.

The water-lithium bromide vapour absorption system is used in a number of

air conditioning applications. This system is useful for applications where the

temperature required is more than 32 degree F.

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Advantages of absorption system over compression system

No moving part except pump-motor, which is comparatively smaller

than compressor system.

Quiet in operation, low maintenance cost.

Can work only with thermal energy as an input.

Can be built for huge working capacities. (even for above 1000 TR)

Can be operated at designed C.O.P’s or even at part loads by varying

generator temperature.

Space and Auto. control requirements favour absorption system.

Types of Refrigerants

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1. Halo Carbons

2. Azeotropic Refrigerants

3. Zeotropic Refrigerants

4. Inorganic Refrigerants

5. Hydrocarbon Refrigerants

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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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Inorganic RefrigerantsCarbon Dioxide

Water

Ammonia

Air

Sulphur dioxide

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Azeotropic RefrigerantsA stable mixture of two or several refrigerants whose vapour

and liquid phases retain identical compositions over a wide

range of temperatures.

Examples : R-500 : 73.8% R12 and 26.2% R152

R-502 : 8.8% R22 and 51.2% R115

R-503 : 40.1% R23 and 59.9% R13

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Zeotropic RefrigerantsA 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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Hydrocarbon RefrigerantsMany hydrocarbon gases have successfully been used as refrigerants in

industrial, commercial and domestic applications.

Examples: R170, Ethane, C2H6

R290 , Propane C3H3

R600, Butane, C4H10

R600a, Isobutane, C4H10

Blends of the above Gases

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Environmental Effects of Refrigerants

- Depletion of the ozone layer in the stratosphere

- Global warming :

Refrigerants directly contributing to global warming when released to the

atmosphere

Indirect contribution based on the energy consumption of among others

the compressors ( CO2 produced by power stations )