Absorption heat pump cycles for simultaneous space conditioning and graywater purification

A thermodynamic model of an open-loop absorption heat pump cycle with integrated membrane-based water purification processes is developed for graywater purification and space conditioning. Two water purification processes are considered: forward osmosis and membrane distillation. The cycle is simulated over a wide range of water loads, and the performance of the cycle is calculated with each purification method. For low water loads, the cycles perform identically, while for high water loads, the membrane distillation cycle performs better than the forward osmosis cycle. Parametric studies are conducted on the water recovery, evaporator temperature, and graywater inlet temperature for the membrane distillation cycle. With some optimization, the energy ratio of the cycle, which peaks around 1.6 normally, can be increased to above 1.75.