In these slides I have discussed about vapour absorption.

1. jahangirabad institute of technology

2. Simple vapour absorption system
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3. 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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4. Practical vapour absorption system
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5. Practical vapour absorption system
 The 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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6. Ammonia Hydrogen (Electrolux)
Refrigeration system
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7. 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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8. Lithium Bromide Absorption system
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9. 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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10. 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.
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11. Types of Refrigerants
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1. Halo Carbons
2. Azeotropic Refrigerants
3. Zeotropic Refrigerants
4. Inorganic Refrigerants
5. Hydrocarbon Refrigerants

12. 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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13. Inorganic Refrigerants
 Carbon Dioxide
 Water
 Ammonia
 Air
 Sulphur dioxide
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14. Azeotropic Refrigerants
 A 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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15. 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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16. Hydrocarbon Refrigerants
 Many 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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17. 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 )
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