As an essential operation parameter of a direct-expansion solar-assisted heat pump (DX-SAHP) system, the degree of subcooling has influence on the thermal performance of the system. Based on the original experimental setup, a throttling valve and a liquid receiver are added at the outlet of the condenser to control degree of subcooling, forming a new system. A quasi-dynamic mathematical model of the new system has been developed to analyze the effect of subcooling on the system performance, and the iterative criterions for the model convergence are degree of superheat and degree of subcooling. The simulation results show that, the heating capacity per unit refrigerant mass is sensitive to the variation of degree of subcooling at the lower degree of subcooling, while the compressor power per unit refrigerant mass is sensitive to that at the higher degree of subcooling. The maximum heating coefficient of performance (COP) of the new system occurs when the degree of subcooling remains constant at 4 K. In the four typical days, the heating COP values of the new system with a constant degree of subcooling of 4 K are 9.13%, 14.35%, 9.42% and 5.73% higher than that of the original system, respectively. Moreover, the parametric study shows that the DX-SAHP system can achieve better performance in term of heating COP by controlling the degree of subcooling in the range of 2–5 K.

作为直接膨胀式太阳能辅助热泵（DX-SAHP）系统的基本运行参数，过冷程度会影响系统的热性能。基于原始实验设置，在冷凝器的出口处增加了节流阀和液体接收器，以控制过冷度，从而形成一个新系统。已经开发了新系统的准动态数学模型来分析过冷度对系统性能的影响，模型收敛的迭代标准是过热度和过冷度。仿真结果表明，在较低的过冷度下，每单位致冷剂质量的加热能力对过冷度的变化敏感，而单位制冷剂质量的压缩机功率对较高的过冷度敏感。当过冷度保持恒定在4 K时，将出现新系统的最大性能系数（COP）。在典型的四天中，恒定过冷度为4 K的新系统的加热COP值为9.13。分别比原始系统高出％，14.35％，9.42％和5.73％。此外，参数研究表明，通过将过冷度控制在2–5 K范围内，DX-SAHP系统可以在加热COP方面实现更好的性能。恒定过冷度为4 K的新系统的加热COP值分别比原始系统高9.13％，14.35％，9.42％和5.73％。此外，参数研究表明，通过将过冷度控制在2–5 K范围内，DX-SAHP系统可以在加热COP方面实现更好的性能。恒定过冷度为4 K的新系统的加热COP值分别比原始系统高9.13％，14.35％，9.42％和5.73％。此外，参数研究表明，通过将过冷度控制在2–5 K范围内，DX-SAHP系统可以在加热COP方面实现更好的性能。