The transcritical CO₂ heat pump is widely used due to its higher efficiency. Frost is inevitable at low ambient temperature, resulting in a deteriorated coefficient of performance and heating capacity. Considering the disadvantages and limitations of other defrosting methods, the hot gas bypass defrosting method was experimentally investigated in this paper. The dynamic characteristics of pressure and temperature during the defrosting process are studied in detail and the pressure-enthalpy diagrams are depicted. In addition, energy analysis of the heat supply and energy consumption is presented to evaluate the defrosting efficiency. Furthermore, the influence of ambient temperature is also discussed. The results show that the measured parameters change gradually during the defrosting process except for the initial stage and defrosting time is within the defrosting regulations. The defrosting efficiency is evaluated to be 41.16%–50.84% with variation of ambient temperatures, which indicates that the hot gas bypass defrosting method is suitable for the air source transcritical CO₂ heat pump.

跨临界CO ₂热泵因其较高的效率而被广泛使用。在较低的环境温度下不可避免会出现霜冻，从而导致性能系数和加热能力下降。考虑到其他除霜方法的弊端和局限性，本文对热气旁路除霜方法进行了实验研究。详细研究了除霜过程中压力和温度的动态特性，并绘制了压力-焓线图。此外，还对供热和能耗进行了能量分析，以评估除霜效率。此外，还讨论了环境温度的影响。结果表明，除霜初期，除除初始阶段外，所测参数逐渐变化，除霜时间在除霜规定范围内。随着环境温度的变化，除霜效率估计为41.16％–50.84％，这表明热气旁路除霜方法适用于空气源跨临界CO_2个热泵。