Theoretical model of absorption heat pump from ideal solution to real solution: Temperature lift factor model

Abstract

Based on the internal actual physical processes, a new theoretical model for analysis of absorption heat pump (AHP), called temperature lift factor model is built in this paper, which is different from the commonly used equivalent theoretical model: a heat pump combined with a heat engine. The basic performance of heat transformation by AHP is studied by analysis of the novel theoretical model. A factor describing the temperature lift of heat, called temperature lift factor, is defined as the ratio of the temperature difference between the heat source and heat reservoir for the evaporation and absorption process and the temperature difference between the generation and condensing process. It is prompted that the basic performance of AHP could be characterized by the temperature lift factor and the COP. The temperature lift factor and the ideal COP respectively for single effect and single stage AHP, multi-effect AHP and multi-stage AHP are derived, from which we could see the temperature lift factor and COP are relatively independent. Then, for the actual process of AHP, two situations are discussed, first for using the actual solution with infinite solution flow rate, and second for using the actual solution with finite solution flow rate. For these two situations, the descriptions of temperature lift factor and COP are given and the variation laws of temperature lift factor and COP with concentration difference of solution are discussed. Finally, two cases about AHP and absorption heat exchanger (AHE) are given to show applications of the prompted theoretical model.