Experimental study on gas cooler of CO2 water source heat pump water heater

In order to research the effect of the gas cooler on the efficiency of CO2 water source heat pump water heater (WSHPWH), two types of gas coolers (i.e. gas cooler I and gas cooler II) with different structure parameters were designed. At the same time, the corresponding CO2 WSHPWH system I and system II were established. The characteristics of heat transfer of gas cooler I and II were analyzed theoretically. The results indicate that thermal resistances of water side and CO2 side of gas cooler II are smaller than those of gas cooler I and heat transfer coefficient of the gas cooler II is increased by 18% comparing with that of gas cooler I. Thermodynamic perfectibility and relative thermodynamic perfectibility index were applied to evaluating the performance of the above systems. The experimental results confirm that the heat transfer coefficient of the gas cooler II is generally higher than that of the gas cooler I under the experimental compared conditions, and the average value is increased by about 5%. Furthermore, when evaporating temperature is 0°C, thermodynamic perfectibility of system II (ηh, II)is around 16% higher than that of system I(ηh, I).