Development of lithium bromide-water absorption heat pump system for simultaneous production of heated-up air and steam from waste heat

Abstract

Paper presented to the 10th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Florida, 14-16 July 2014.

Absorption heat pumps (AHPs) operate by refrigeration techniques that use heat without requiring a compressor. In this study, an innovative AHP system is proposed that uses waste heat at 80 °C to produce hot air (at least 120 °C), which can be used for applications such as drying, and to simultaneously generate steam of 100–115 °C. Air is heated directly by heat exchange in the absorber working in the heating mode of a LiBr/H2O AHP system. Steam is then produced by heat exchange with the absorption solution, which is still at high temperature. The performance of a bench-scale AHP was evaluated by examination of running in a continuous mode. The tested AHP achieved a hot air temperature of more than 120 °C at the outlet of the absorber, and steam up to 115 °C was simultaneously generated by recovering heat from 80 °C hot water. The coefficient of performance, 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, but temperature in the evaporator was a significantly sensitive factor for the increasing temperature in this proposed AHP system.