空气源热泵结霜/除霜特性的数值模拟

Numerical Simulation of Frosting/Defrosting Characteristics of Air Source Heat Pump

为研究空气源热泵的结霜与除霜特性,建立了热泵系统结霜动态模型和显热除霜模型,求解模型获得了结霜与除霜过程中各系统参数变化规律。结果表明,初期霜层对系统性能影响较小;当结霜工况运行70 min时,系统性能系数(COP)、制热量和蒸发压力降幅分别为6.9%、10.9%和12.3%;随着霜层继续生长,系统性能衰减加剧;除霜工况下,管壁温度迅速升高,霜层预热后进入融霜阶段,从蒸发器入口微元到出口微元,融霜时间从7 s增加到52 s;进入融霜水蒸发阶段后,管壁温度增速减慢,沿制冷剂流动方向融霜水蒸发时间逐渐增加;当换热器散热与得热达到平衡时,管壁温度维持恒定。

A dynamic frosting model and a sensible heat defrost model of air source heat pump system were developed to investigate the frost and defrost characteristics, the variation of system parameters under frosting and defrosting were obtained. The results show that, at the early stage of frosting, the frost has a slight effect on the system performance;after 70 minutes, the decrements of coefficient of performance （COP）, heating capacity and evaporating pressure reached to 6.9%, 10.9%and 12.3%, respectively. The system performance reduced rapidly with the frost growing. Under defrost conditions, the frost changed into defrost stage after preheat as the wall temperature increased rapidly, and the defrost time of inlet section and outlet section increased from 7 seconds to 52 seconds. In the evaporation stage of defrosting water, the wall temperature growth decreases, and the evaporate time increases in the direction of flow of the refrigerant. When the heat gain and heat loss of the exchanger reach balance, the wall temperature finally maintained constant.