Thermal storage technology with phase change material (PCM) is one of the important ways to improve the utilization efficiency of solar energy. A hot water tank experimental system with sodium acetate trihydrate ball as PCM was built. The thermodynamic characteristics based on the temperature in the water tank were tested under an initial water temperature of 80 ℃ and inlet water temperature of 5 ℃. According to the change of water temperature in the tank with the dimensionless time

a filling efficiency analysis method was used to analyze the thermal stratification characteristics of the hot water tank with PCM. This analysis includes the curve of temperature change and filling efficiency when the water flow rates were 1

3

5

7

and 9 L/min

respectively. The experimental results show that when the water tank temperature is 80 ℃

the energy of the ordinary water tank and the hot water tank with PCM are 18.81 MJ and 19.34 MJ respectively. When the water flow rate is the same

the closer the ball with PCM is to the water tank inlet

the better the heat stratification effect of the water tank is. The thermal stratification effect of the ordinary water tank is stronger than that of water tank with PCM when the ball is at the first

second

and third layers

but weaker than that of water tank with PCM when the ball is at the fourth layer. When the inlet flow rate is 9 L/min

the filling efficiency of water tank with PCM is 0.497 and 0.581 when the ball is in the first layer and the fourth layer

respectively

and the filling efficiency of the ordinary water tank is 0.573

when t*=1. As the water flow rate increases

the mixing degree of the hot and cold water increases

and the thickness of the thermocline layer in the water tank increases

which decreases the stratification effect. When the inlet flow rate is greater than 7 L/min and the PCM ball is at the bottom

the thermal stratification characteristics of the hot water tank with PCM are optimal.