Reverse cycle defrosting is widely used for air source heat pumps. When a multi-circuit heat exchanger is vertically installed in a heat pump as an outdoor coil, the melted frost could be kept downwards flowing or locally drained during defrosting by using water collecting trays. To analyze the performance differences of melted frost, two defrosting models were developed and previously reported by authors. In this study, the defrosting performance of an air source heat pump was numerically investigated based on the two models, with the melted frost downwards flowing away or local drainage considered. The following physical parameters are predicted and analyzed, including the thermal resistance of refrigerant, temperature of melted frost on tube and fin’s surface, mass of melted frost and energy consumption from refrigerant during defrosting. As calculated, after the melted frost locally drained, the predicted total energy consumption could be decreased from 898.1 kJ to 727.5 kJ, and defrosting efficiency increased from 47.5% to 57.6%. This work is helpful to optimizing the intelligent control strategy of an air source heat pump unit, as well as saving energy for buildings.

逆循环除霜广泛用于空气源热泵。当多回路换热器作为室外盘管垂直安装在热泵中时，可以使用集水盘将融化的霜保持向下流动或在除霜期间局部排出。为了分析融化霜的性能差异，开发了两种除霜模型，作者先前曾进行过报道。在这项研究中，基于这两个模型，对空气源热泵的除霜性能进行了数值研究，考虑了融化的霜向下流走或考虑局部排水的情况。对以下物理参数进行了预测和分析，包括制冷剂的热阻，管子和散热片表面上融化的霜的温度，融化的霜的质量以及除霜过程中制冷剂的能耗。经计算，融化的霜冻局部排出后，预计总能耗可从898.1 kJ降低至727.5 kJ，除霜效率从47.5％提高至57.6％。这项工作有助于优化空气源热泵机组的智能控制策略，并为建筑物节省能源。