空气源热泵热水器水箱加热动态特征及对水温分布的影响

Dynamic characteristics of water tank heating of air source heat pump water heater and its influence on water temperature distribution

采用COMSOL Multiphysics 5.4软件对热泵热水器水箱加热过程进行动态模拟,实测冷凝器表面温度并进行拟合作为水箱加热输入条件,并基于水箱平均温度及传感器温度的实验与仿真对比验证了模拟的可靠性。结果表明近壁面水受热向上自然对流,在顶部对冲后转沿中轴线向下流动;底部水受铜管冷凝器加热后向上流动。两股水流汇合后折向两边流向水箱壁面,在水箱两侧均形成上、下两个环流区域,使水温在水平和竖直两个方向均存在非均布现象:竖直方向水温上高下低分层,上下温差3~6℃;水平方向水温由壁面到中心先急剧降低后缓慢上升,近壁面存在0.005 m的温度边界层,边界层内温降超过5℃。研究结果可为热泵热水器水箱加热性能提升提供理论参考。

COMSOL Multiphysics 5.4 software was used to dynamically simulate the water tank heating process of the heat pump water heater.The measured temperature of the condenser was assumed to be the input parameter for the tank heating.The reliability of the simulation was verified by comparing the average temperature of the water tank with the experimental values of the sensors.Results show that the water near the wall is heated and flows upwards by natural convection,then turns to flow downwards along the central axis after the topmost confluence.The bottom water is heated by the copper tube condenser and flows upwards.After the two streams of water converge,they flow to either side of the tank wall,forming two circulation zones on either side of the tank,so that the water temperature is distributed in homogeneously in the horizontal and vertical directions.Along the vertical direction,the water temperature is higher on the top and lower at the bottom,and the temperature difference between the upper and lower is 3~6℃.The water temperature decreases sharply along the horizontal direction from the wall to the center and then rises slowly.There is a temperature boundary layer of 0.005 m near the wall,and the temperature in the boundary layer drops more than 5℃.The present work can serve as a theoretical reference for improving the heating performance of the heat pump water heater tank.