Investigation on LiBr-H2O double evaporation-absorption heat pump (DEAHP) for heat recovery under lower driving sources

The absorption heat pump (AHP) is an efficient alternative to the conventional fuel-based heating system. However, the coefficient of performance (COP) is decreased sharply when the available driving source temperature drops, which even leads to out of work of AHP when recovering low grade heat. The DEAHP could run efficiently when temperatures of both the driving source and waste heat are in low grades, and an experimental prototype is manufactured for performance investigation. The COP could reach 1.88 during the experiment, and the highest concentration of LiBr solution is lower than 60%, thus, there is no risk of crystallization of DEAHP. Besides, the payback period of DEAHP is less than 2 years when compared with the common plate heat exchanger at the thermal substation. Besides, the performance improvement of heat recovery contributed by DEAHP is significant, which could extend capacity of heating network and reduce energy consumption for district heating systems.