Lithium bromide/water absorption heat pump for simultaneous production of heated air and steam from waste heat

Absorption heat pumps (AHPs) operate by refrigeration techniques that use heat without a compressor. In this study, proposed is the innovative LiBr/H₂O AHP system which utilizes waste heat at 80°C to produce both hot air of 120°C (at least) and steam of 100-115°C. Air is heated directly by heat exchange in the absorber at the heating mode. Steam is produced by heat exchange with the absorption solution still having high temperature. The performance of a bench-scale AHP was evaluated under the continuous operation. By recovering heat of hot water at 80°C, the temperature of hot air achieved more than 120°C at the outlet of the absorber and that of steam became up to 115°C. The energy efficiency ratio, which is defined as the ratio of heat generated to the power consumed for pumping fluid, exceeded 20. The heat transfer rate in the absorber was dominated by an air stream through a bundle of tubes, and the temperature in the evaporator was a significantly sensitive factor to increase the temperature in this AHP system.