CO2跨临界热泵系统特性再分析

在原有研究的基础上，结合实际系统，本文对CO₂跨临界热泵系统的特性进行再分析，通过参数计算，分析回热温度、气体冷却器出口温度、运行压力三种因素如何影响系统性能，提出提高CO₂热泵运行效率的方法。分析结果表明：回热器并不总有效，而是与气体冷却器出口温度有关，当温度小于某临界值时回热会降低系统运行制热性能系数COP_h，当温度大于此临界值时回热则有助于提高COP_h；对应气体冷却器出口温度存在最优压力，但实际压缩机的可承受压力是有限的，导致系统在某些气体冷却器出口温度下不能在最优压力下运行，同时在不同的排气压力下，存在气体冷却器出口温度最高限定值，否则COP_h不合理也不可接受；热泵出水温度以及气体冷却器出口温度共同影响系统排气压力的选择。

Reanalysis of characteristics of CO2 transcritical heat pump system

Based on the original research, the characteristics of CO₂ transcritical heat pump system were reanalyzed combined with the actual system. How regenerative temperature, outlet temperature of gas cooler and operating pressure affect system performance was analyzed by parameter calculation. Methods to improve the efficiency of CO₂ heat pump operation were proposed. The analysis results showed that intermediate heat exchanger (IHX) is not always effective, but related to outlet temperature of gas cooler. When the temperature is lower than a certain critical value, IHX will reduce system operating efficiency COP_h. When the temperature is higher than the critical value, it will help to increase COP_h. There existed an optimum pressure corresponding to the outlet temperature of gas cooler, but the actual compressor’s tolerable pressure is limited, resulting in the system not operating under the optimum pressure at some outlet temperatures of gas cooler. Meanwhile, under different exhaust pressures, there existed the maximum limit values of outlet temperature of gas cooler, otherwise, the COP_h is unreasonable and unacceptable. The outlet water temperature and the outlet temperature of gas cooler affect the choice of exhaust pressure together.