Performance analysis on modified cycle of double absorption heat transformer with solution and coolant heat regeneration

A modified cycle of double absorption heat transformer with heat regeneration of both solution and coolant is proposed by adding a heat exchanger at the inlet of coolant and outlet of dilute solution of the absorber-evaporator. The performances of three cycle schemes of double absorption heat transformers without regeneration, with solution heat regeneration and with both solution and coolant heat regeneration for absorber-evaporator are calculated and compared. The results show that the double absorption heat transformer with both solution and coolant heat regeneration has a wider operating range of absorption-evaporation temperature and higher coefficient of performance (COP) and exergy efficiency. When the temperatures of absorption, generation, condensation and absorption-evaporation are respectively 120-150 °C, 70 °C, 25 °C and 80-115 °C, the average values of COP or exergy efficiency of the new cycle is 8-9% and 2.5-3.5% respectively higher than the ones without heat regeneration and with solution heat regeneration only. The variation trends of COP and exergy efficiency of three cycles versus the temperatures of absorption-evaporation, condensation, generation and absorption are also presented. The impacts of absorption-evaporation temperature on COP and exergy efficiency under different temperature combinations of generation, absorption and condensation are presented for optimal design of the new double absorption heat transformers.