Design, Optimization and Techno-Economic Feasibility Study of Absorption Refrigeration System Using Ammonia + Water As Working Pair

Abstract

Absorption refrigeration systems are the cooling systems that use heat as input for operation instead of electricity. This type of refrigeration system reduces the fossil fuel consumption, indirectly restricts the CO2 emission to the atmosphere, and restricting at the same time the usage of toxic refrigerants. They generally use refrigerant/absorbent pair for operation. NH3+ H2O and LiBr+H2O are the most common working pair available in the market. In ammonia-water system, the absorbent is water, generally weak solution of ammonia-water and the refrigerant is ammonia. Ammonia + water as the working pair is taken and the cycle was operated for various temperature ranges of the evaporator, generator and absorber, we also worked on different no. of stages to check the COP of the system. The evaporator temperature has a very insignificant effect on the COP of the system and thus does not change the COP even if we increase the temperature. The generator has a very vivid impact on the COP. As we increase the generator temperature the COP value decreases. Thus further concreting our base for using low grade heat as the source of power for operating the generator. Further no. of stages of the separator also effects the COP of the system. Increasing the no. of stages increases the COP up to a certain level but on further increasing the stages the COP becomes constant. Thus the optimum conditions comes as- TG = 70 C, TE = 5 C, TC = 33 C, TA = 30 C and the optimum no. of stages for the separator comes to 8.The feasibility study also suggests that the use same capacity (1.5TR) ARS instead of VCR is profitable by an amount of INR 8.5 K annually. From the feasibility analysis we observe that for a refrigeration of 1 TR, we require 23 MWh low grade heat at a temperature of 70ºC. Further, if we change the refrigeration load the requirement of low grade heat also changes.