Experimental Investigation of Trans-critical CO2 Heat Pump High-Temperature Water Heater

This paper studied the influence of parameters such as discharge pressure, outlet temperature of water, compressor frequency and expansion valve opening degree on the performance of a trans-critical CO2 heat pump high-temperature water heater. There is an optimal discharge pressure for different water outlet temperature, and the optimal discharge pressure increases with the increase of inlet water temperature, at the same time the system performance decreases. Results also indicated that the system COP increases first and then decreases with the increase of the evaporation pressure. The effect of compressor frequency on system performance under the same opening degree of expansion valve is studied. Results showed that a maximum COP of 3.9 is reached when the compressor frequency is 85 Hz. © 2018, Science Press. All right reserved.