The general performance characteristics of an irreversible absorption heat pump operating between four temperature levels

An irreversible cycle model of an absorption heat pump operating between four temperature levels is set up and used to analyse the performance of the heat pump affected by the irreversibility of finite-rate heat transfer and the internal irreversibilities of the working material. The coefficient of performance of the heat pump is optimized for a given specific heating load. A fundamental optimum relation is derived, from which the characteristic curves of the dimensionless specific heating load versus the coefficient of performance are generated. The influence of the internal irreversibilities on the performance of the system is discussed. The optimal distribution of the heat-transfer areas of the heat exchangers is determined. Some special cases are analysed. The results obtained can describe the optimal performance of a four-temperature-level absorption heat pump affected simultaneously by the internal and external irreversibilities and can provide the theoretical bases for the optimal design and operation of real absorption heat pumps operating between four temperature levels.