Abstract: 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.

Key words: Air source heat pump water heater, Water tank heating, Dynamic characteristics, Water temperature distribution