Experimental research on geothermal heat pump system with non-azeotropic working fluids

The subject of the paper is how to solve the problem of heating in some areas and making the best of geothermal waste water through heat pump. Now the biggest barrier is to find proper working fluids, which can work in the condition of 80–100 °C as condensation temperature and 25–35 °C as evaporation temperature, and at the same time keep the highest pressure in the system under 2500 kPa. Experimental results show that new working fluids R123/R290 (50/50 by mass %) and R123/R290/R600a (40/50/10 by mass %) will meet the requirement of the new working condition. The coefficient of performance of the geothermal heat pump system using the working fluids is above 3.0 with condensation temperature above 80 °C and condensation pressures below 2500 kPa. In the end of the paper, some improvements are proposed for the purpose of better performance. In the paper, the thermodynamic properties of mixtures are calculated with REFPROP 6.1.