ENERGY AND EXERGY ANALYSIS OF AMMONIAWATER DOUBLE EVAPORATOR VAPOUR ABSORPTION REFRIGERATION SYSTEM

Abstract

The energy and exergy analysis of “ammonia-water double evaporator vapour absorption refrigeration system (NH3−H2O DE VARS)” have been done in this correspondence. The energy analysis of double-evaporator vapour absorption cycle involves the determination of coefficient of performance (COP) at various operating conditions and study the effect of the variation of both the evaporator temperature (i.e. Te1& Te2), generator temperature (i.e. Tg1& Tg2), absorber temperature (i.e. Ta1& Ta2), condenser temperature and other parameters on the COP. It is observed that by using double evaporator NH3−H2O VAR cycle instead of using simple NH3−H2O VAR cycle having cooling load (20 TR) at low temperature, there is an increase in 11.11% COP in comparison to when the load on both the evaporator is equal i.e. Qe1 = Qe2 = 10 TR and there is an increase of 22.22% in COP when the system is fully operated at high temperature evaporator i.e. Qe1 = 20 TR,Qe2 = 0. It is also observed that the optimum value of COP is obtained at the temperature of 363° K and 383° K and at the pressure of 11.5 bar & 12 bar in generator1 & 2 respectively for equal loading of both evaporators i.e. 10 TR. The effect of variation of both the generator temperature (i.e. Tg1& Tg2), absorber temperature (i.e. Ta1& Ta2), evaporator temperature (i.e. Te1& Te2), condenser temperature and solution circulation ratio (SCR-1 & SCR-2) in high pressure and low pressure circuit on the exergetic efficiency (ηex) are also discussed in this communication. Exergy analysis is also performed to calculate the total exergy destruction rate, thermal exergy loss rate and the destruction of exergy in each components of the system. It is observed that the maximum exergy destruction occurs in the solution heat exchanger (shx-1& shx-2) followed by absorbers (absorber-1& absorber-2), evaporators (evap-1& evap-2) and generators (gen1& gen-2). The maximum exergetic efficiency (ηex) occur at a temperature of 358° K and 378° K in generator-1 & 2 respectively. The study shows that NH3−H2O DE VAR systems are more promising than simple VAR systems in a wide operating range of evaporator temperature.