由何宇佳、梁星宇、成家豪、邵亮亮、张春路撰写的论文Approaching optimum COP by refrigerant charge management in transcritical CO2 heat pump water heater在International Journal of Refrigeration 2020年第118卷在线发表。论文针对跨临界二氧化碳热泵热水器的高压控制问题，指出高压控制问题的实质是制冷剂最优充注量的实现问题，提出通过系统设计实现不同运行工况下制冷剂最优充注量基本不变，从而无需优化控制系统高压就能实现不同工况下系统能效的近似最优。仿真计算表明，通过在气冷器出口添加合适尺寸的高压储罐，该方法在不同工况下的平均COP损失（相对于理论最优COP）仅为 -0.2%。该方法的提出，可以显著简化跨临界二氧化碳热泵热水器的控制系统、并提升系统实际运行能效。

论文链接

论文摘要：

Optimal high pressure is crucial to the performance of transcritical CO2 heat pump water heater (HPWH). From the perspective of refrigerant charge management, this work aims to approach optimum COP in CO2 HPWH without high pressure control. By modeling a running CO2 HPWH, we in-depth investigated the relation between optimal high pressure and refrigerant charge. It was found that the essence of optimal high pressure control is to manage optimum refrigerant charge of the system. If the optimum charge of the system could remain constant under any working conditions, the system would operate automatically at optimum COP with fixed refrigerant charge. Then influences of water inlet temperature, water outlet temperature and ambient temperature on optimum refrigerant charge were numerically analyzed. Finally, system design methods to approach optimum COP by minimizing the variation of optimum charge under variable operating conditions were developed. As a result, the average COP loss of fixed-charge system after resizing heat exchangers is only -0.8%. By comparison, with a high-pressure reservoir at the outlet of gas cooler, the average COP loss can be as low as -0.2%.