Vapour absorption system

In these slides I have discussed about vapour absorption.

1. Refrigeration and Air Conditioning NME:604 Unit3 Presented by Mr Naphis Ahmad Assistant professor JETGI Barabanki jahangirabad institute of technology

2. Simple vapour absorption system 12/31/2016 Jahangirabad institute of technology 2

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. 12/31/2016 Jahangirabad institute of technology 3

4. Practical vapour absorption system 12/31/2016 Jahangirabad institute of technology 4

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. 12/31/2016 Jahangirabad institute of technology 5

6. Ammonia Hydrogen (Electrolux) Refrigeration system 12/31/2016 Jahangirabad institute of technology 6

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. 12/31/2016 Jahangirabad institute of technology 7

8. Lithium Bromide Absorption system 12/31/2016 Jahangirabad institute of technology 8

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. 12/31/2016 Jahangirabad institute of technology 9

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. 12/31/2016 Jahangirabad institute of technology 10

11. Types of Refrigerants 12/31/2016 Jahangirabad institute of technology 11 Halo Carbons Azeotropic Refrigerants Zeotropic Refrigerants Inorganic Refrigerants 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 12/31/2016 Jahangirabad institute of technology 12

13. Inorganic Refrigerants Carbon Dioxide Water Ammonia Air Sulphur dioxide 12/31/2016 Jahangirabad institute of technology 13

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 12/31/2016 Jahangirabad institute of technology 14

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%) 12/31/2016 Jahangirabad institute of technology 15

16. Hydrocarbon Refrigerants Many hydrocarbon gases have successfully been used as refrigerants in industrial, commercial and domestic applications. Examples: R170, Ethane, C 2 H 6 R290 , Propane C 3 H 3 R600, Butane, C 4 H 10 R600a, Isobutane , C 4 H 10 Blends of the above Gases 12/31/2016 Jahangirabad institute of technology 16

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 ( CO 2 produced by power stations ) 12/31/2016 Jahangirabad institute of technology 17