Performance analysis of low hot source temperature absorption cooling systems

Abstract

SYNOPSIS Air conditioning systems have a major impact on energy demand. With fossil fuels fast depleting, it is imperative to look for cooling systems that require less high-grade energy for their operation. In this context, absorption cooling systems have become increasingly popular in recent years from the viewpoints of energy and the environment. Two types of absorption chillers, single effect and half-effect cycles, can operate using low temperature hot water. In this paper a comparative study between these two systems with identical cold output is carried out. An efficiency analysis, accounting for both energy and exergy considerations is presented. Simulation results were used to study the influence of the various operating parameters on the coefficient of performance (COP), exergy efficiency and the total exergy destruction of the two systems. The COP of the half-effect system is approximately half the COP of the single effect system but the exergy efficiency of the latter is slightly lower. In this study, when the evaporation temperature was maintained at 4°C, condenser and absorber temperatures varied from 28°C to 38°C and generator temperature varied from 40°C to 110°C, the maximum COP values of the single effect cooling system were in the range of 0.741–0.808 and, for half-effect cooling systems, in the range of 0.408–0.435. The maximum exergy efficiency values of the single effect cooling systems are in the range of 19.6%–29.6% and, for half-effect cooling systems, in the range of 14.7%–22.6%.