27-03-2012, 12:53 PM
Vapor Absorption System
28547005-Vapour-Absorption-System 4.doc (Size: 178.5 KB / Downloads: 139)
VAPOR ABSORPTION CYCLE
Before the development of the vapor compression system of refrigeration, vapor absorption cycle was very widely used. The vapor compression system replaced vapor absorption system because it has high coefficient of performance (COP). The vapor absorption system requires very less amount of electricity but large amount of heat; hence it can be used very effectively in industries where very large stocks of excessive steam are available. In such cases there is not only effective utilization of steam, but also lots of savings in electricity costs. Of late the vapor absorption systems are being employed by a number of industries to save on their electric bills. However, the vapor absorption system is useful only where large scale refrigeration in excess of at least 20 tons is required.
VARIOUS PROCESSES OF VAPOR ABSORPTION CYCLE
The various processes of the vapor absorption cycle are similar to the one in vapor compression cycle, only the method of compression of the refrigerant is different. In vapor absorption system ammonia is used as the refrigerant, which has very high affinity to dissolve in water. Here are various processes of vapor absorption cycle:
WORKING
Some liquids like water have great affinity for absorbing large quantities of certain vapors (NH3) and reduce the total volume greatly. The absorption refrigeration system differs fundamentally from vapor compression system only in the method of compressing the refrigerant. An absorber, generator and pump in the absorption refrigerating system replace the compressor of a vapor compression system. Figure shows the schematic diagram of a vapor absorption system. Ammonia vapor is produced in the generator at high pressure from the strong solution of NH3 by an external heating source.
APPLICATION
THE PRINCIPLE FUNCTION OF AN ABSORPTION CHILLER
The absorption chiller is a machine to produce chilled water by using heat such as steam, hotwater, gas, oil.
Pure water is used as refrigerant and lithium bromide solution is used as absorbent.
Chilled water is produced by the principle that liquid, which evaporates easily, absorbs heat from surrounding when it evaporates.