Theoretical study on a modified heat pump cycle with zeotropic mixture R32/R290 for district heating in cold region

This paper proposes an ejector enhanced internal auto-cascade heat pump cycle (EIHP) with zeotropic mixture R32/R290 for district heating in cold region. The internal auto-cascade and ejector techniques are applied for enhancing the system performance. Performances of the EIHP are investigated by using a developed thermodynamic model. The simulation results indicate that as the evaporator outlet temperature ranges -25 degrees C to 5 degrees C, EIHP yields 199% higher COP and 37-12% higher volumetric heating capacity over the conventional heat pump cycle (CHP) at a fixed condenser outlet temperature of 60 degrees C. Moreover, to evaluate the system performance in detail, the other critical parameters are investigated including condenser outlet temperature, refrigerant mass fraction of R32, ejector performance and so on. Generally, the EIHP system can obtain a significant performance enhancement for district heating applications.