This paper is concerned with an improvement in the conventional absorption heat pump cycle that allows for achieving an increased temperature boost and a better coefficient of performance (COP). The improvement is obtained by adding adiabatic absorption and desorption steps to the absorber and desorber of the system, respectively. The adiabatic processes make it possible to obtain the highest possible temperature in the absorber before any heat is removed from it and the lowest temperature in the desorber before heat is added to it. This, in turn, allows for efficient utilization of the thermodynamic availability of the heat supply stream. Compared to the conventional cycle, the improved system can operate with a larger difference between the high and low concentrations, less circulation losses, and a more efficient heat exchange.

The concept of adiabatic absorption and desorption is described and compared for the conventional and improved cycles. Mathematical expressions are derived for the conditions at the adiabatic points, and design considerations are described for incorporating the improvements in a conventional system. Computer-generated performance curves of COP versus temperature boost are given for the heat pump to illustrate the performance enhancement by the adiabatic process.