跨临界CO_2热泵气体冷却器对系统性能及最优排气压力的影响

为了研究气体冷却器换热面积及其内部制冷剂质量流速对跨临界CO2热泵热水器系统性能及其最优排气压力的影响,本文建立了变换热面积和变质量流速的气体冷却器数学模型,通过理论计算得出,在一定范围内,当CO2质量流速不变时,增加气体冷却器的换热面积可以提高系统制热量及制热能效比;但由于压降的影响,增加气体冷却器内CO2质量流速而换热面积不变时,系统的性能系数会先上升后降低。同时,气体冷却器换热面积的增加会使系统的最优排气压力降低,气体冷却器内CO2质量流速的升高会使系统的最优排气压力升高,因此在跨临界CO2热泵设计中,确定气体冷却器换热面积及质量流速对系统获得较高的COP并维持最优排气压力有着重要意义。

The Effects of the Gas Cooler on Both the System Performance and the Optimal Discharge Pressure at a Transcritical CO2 Heat Pump

In order to research the effects of the gas-cooler heat transfer area and the mass velocity in the gas-cooler on the system performance and the optimal discharge pressure of a transcritical CO2 heat pump water-heater, a gas-cooler mathematical model in which the heat transfer area and the mass velocity in it can be changed separately was built in this paper. The results show that the heating capacity and COP increase as the heat transfer area increases when the mass velocity is constant. Moreover, COP increases first and then declines with an increase in the mass velocity due to the influence of the pressure loss when the heat transfer area is constant. Additionally, the optimal discharge pressure declines as the heat transfer area increases, and it increases with an increase in the mass velocity. Thus, it should be considered properly to discuss the gas-cooler heat transfer area and the mass velocity in it to achieve superior COP and maintain the optimal discharge pressure when designing the transcritical CO2 heat pump.