R410A/R134a双级耦合热泵系统最优中间水温实验研究

The cascade heat pump system can overcome such problems as the deteriorated heating capacity and low coefficient of performance (COP) in conventional air source heat pump system under low temperature conditions. However, when other parameters of the cascade system are constant, its performance will be affected by the intermediate water temperature. Based on the simple operation analysis of the cascade heat pump system, an R410A/R134a cascade heat pump platform was designed and tested under various conditions when the condensing temperature, evaporating temperature and intermediate water temperature were ranged within 50-75 ℃, -30-10 ℃ and 15-35 ℃, respectively, in order to reveal the main factors influencing the optimal intermediate water temperature. The experimental results show that when keeping other parameters constant, the coefficient of performance increases firstly and then drops with the intermediate water temperature, and that there always exists an optimal intermediate water temperature corresponding to the maximum COP value. According to the experimental data, it can be found that the optimal intermediate water temperature increases with the evaporating temperature in low-temperature cycle, and the condensing temperature in high-temperature cycle and is more affected by the evaporating temperature. By changing external factors such as the ambient temperature and water temperature, a function correlation of the optimal intermediate water temperature with evaporating temperature and condensing temperature as the independent variables is obtained by fitting a large number of experimental data, which could provide a guidance to the optimization on actual operation of the R410A/R134a cascade heat pump system.