Assessment of a two-stage compression heat pump cycle using mixture R290/R744 for water heater applications.

In this study, the mixture R290/R744 were chosen as promising alternative refrigerants in a two-stage compressor heat pump cycle and their performance potentials were evaluated by using the developed mathematical model. As the additive amount of R744 in the refrigerant mixture increases from 5% to 15%, the progressive rise in volumetric heating capacity is presented, but the heating COP tends to decrease while the system pressure rises. When the mass concentration of R744 varies from 5% to 15%, the volumetric heating capacity increases by 412.72 KJ m-3 and the heating COP reduces by 0.79 on average under the evaporator outlet temperature varies from -30 to 20 °C. Considering the potential in reducing the irreversibility of heat exchangers, however, the zeotropic refrigerant R290/R744 can yield very attractive advantage in heat pump water heater applications due to its larger gliding temperature features.

本研究选取R290/R744混合物作为双级压缩热泵循环中极具潜力的替代制冷剂，并通过所建立的数学模型评估其性能潜力。当混合制冷剂中R744的添加量从5%增至15%时，容积制热量呈逐步上升趋势，但制热COP（Coefficient of Performance）趋于下降，同时系统压力升高。在蒸发器出口温度范围为-30至20°C时，当R744的质量浓度从5%变化至15%，容积制热量平均增加412.72千焦/立方米，制热COP平均降低0.79。然而，考虑到其在降低换热器不可逆性方面的潜力，非共沸制冷剂R290/R744凭借其更显著的滑移温度特性，在热泵热水器应用中可展现出极具吸引力的优势。