A NEW TREND IN HEAT-RECOVERY FROM WASTES BY USE OF PARTIALLY MISCIBLEWORKING FLUIDS

In an absorption heat pump, the separation of the miscible mixture is a great energy consumer, which significantly limits the COP of the sys tem. We propose a new heat pump concept in which the working fluid is a partially miscible mixture. These solutions exhibit very dissymetric properties depending on the pressure level: Under low pressure and te mperature, the mixture is composed of two immiscible phases in thermod ynamic equilibrium. Then any solution spontaneously splits into these two liquid phases by simple decantation without any energy supply. Thi s phenomena is called demixtion. Another important fact is that the de gree of miscibility increases with the pressure and so, beyond a criti cal pressure of dissolution the two earlier immiscible phases become c ompletely miscible and form an homogeneous liquid phase. In this condi tion, at high temperature, the volatile phase is evaporated and its va por is absorbed in the non-volatile phase, exactly in the same process and equipment as in the case of a classical absorption heat pump. For this new process, the COP is 100 to 200 times higher than that for th e conventional heat pump. (C) 1997 Elsevier Science Ltd.