Performance optimization for an irreversible four-temperature-level absorption heat pump

The optimal performance of an absorption heat pump operating between four temperature levels with the losses of heat resistance and internal irreversibility is analyzed first by taking the total heat-transfer area of heat exchangers as an objective function. The minimum total heat-transfer area is described in terms of the rate of the entropy changes of four heat reservoirs, and the generally optimal relation among the heating load, the coefficient of performance and total heat-transfer area is achieved. Then, an ecological optimization criterion is proposed for the best mode of operation of the absorption heat pump. We investigate the ecological optimization performance and derive the optimal heating load, coefficient of performance and entropy production rate at the maximum ecological criterion for the absorption heat pump. Effects of thermal reservoir temperature and the internal irreversibility on the ecological function have been discussed.