Chapter – 02
Vapour Absorption Systems
- Simple vapour absorption system
The function of compressor in this system is to take-out the vapour from evaporator and compresses it then to condenser pressure at a temperature more than saturation temperature corresponding to condenser pressure. Below figure shows the simple vapor absorption system. Following are the vital components of the system absorber, condenser, expansion valve, pump and reducing valve.
Generally refrigerant used for such system are ammonia or aqua ammonia. Strong ammonia solution contains as much as ammonia as it can and weak solution contains less ammonia. The compressor of vapour compression system is replaced by above mentioned component. The heat flow in system is generated and work is supplied to pump. The weak solution containing a very little ammonia is spread by in absorber. This strong solution from absorber is pumped into generator. The weak solution contains the added heat in ammonia. This function of compressor is done by elements like generator, pump and reducing valve.
- Practical vapour absorption system.
The simple absorption system consist of minimum number of parts/components for its functioning but in actual practice COP of the system is very low. For getting higher COP modification is done in simple absorption system. Heat Exchanger, analyzer and rectifier are added in circuit. Below figure shows Practical or Actual vapor absorption system.
- Heat Exchanger
To increase the COP of system strong solution must get heated and weak solution coming out from generator must be cooled. Therefore, to achieve this exchanger is added in the actual system.
- Analyzer
Analyzer is provided to remove unwanted particles absorbed with ammonia vapour system before going to condenser. The particle (Generally Water) enters in expansion valve where they freeze and choke the pipe line. Analyzer is direct contact type consisting of series of trays above generator.
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