O2热泵热水器系统稳态模拟与运行参数研究

he steady state model was developed for a carbon dioxide heat pump water heater, including a compressor, a tube-in-tube gas cooler, an electronic expansion valve and a finned-tube evaporator. The moving boundary method was used in the heat exchanger model considering both calculation accuracy and efficiency. Two control schemes were taken into account in the system level model: the expansion valve opening is kept constant; or the high-side pressure is kept constant, and especially it is the optimum high-side pressure, which presents the maximum COP. Based on the model, system performances were predicted under different working conditions. The results show that there is good quantitative agreement between the model prediction results and the experimental data. Furthermore, the effects of some key parameters were discussed for the purpose of optimal design.