| In recent years,China’s economy has developed rapidly.People’s requirements for the comfort of buildings have become higher and higher,and building energy consumption has also remained high,Therefore,the new era has put more stringent requirements on energy-saving design of buildings.Taking advantage of China’s abundant solar energy resources,in order to solve the contradiction between solar energy utilization and building energy use in time,energy storage technology came into being,using phase-change materials to store energy during the phase-change process to realize the use of solar energy across time.This paper proposes a phase-changing thermal storage structure that uses solar energy as a heat source and air as a heat transfer medium,This structure integrates the phase change heat storage plate and the heat collection plate,and utilizes the temperature difference between the heat collection side and the heat storage side to naturally circulate air to transfer the heat from the heat collection side to the PCM of the heat storage side.In addition,the heat transfer performance of the structure is studied,the main work and conclusions are listed as follows:(1)A phase change heat storage structure was designed and a corresponding heat transfer model was established and the numerical simulation of the heat storage process was carried out.Based on the simulation results,the scheme is compared and optimized to reduce the air flow resistance.The numerical simulation results show that if the heat flux is 300W/m~2 for 8 hours,the liquid phase ratio of the PCM reached 79.8%.In the heat storage process,as the heat storage time increases,the temperature difference between the heat collection side and the heat storage side decreases,and the average flow velocity in the channel drops significantly,which has a greater impact on heat transfer.(2)Decanoic acid-lauric acid eutectic were used as PCM,a heat storage plate was designed,which was integrated with a flat plate heat collector to form a phase change heat storage wall.The electric heating plate was used to simulate solar flat plate heat collector for heat collection.The experiment room tested the heat storage performance and heating effect of the phase change heat storage wall.The results show that when the heat flux density of the collector plate is 300W/m~2,the heat collection time is 8 hours per day.During the test,the temperature of the phase change heat storage room is 2.6℃ higher than that of the control room on average,and the maximum temperature difference is 5.6℃.At the end of heat storage and the beginning of heat release,the temperature difference is the largest,the maximum temperature difference is 4.6℃,the liquid phase rate is judged by the temperature of the measuring point,and the liquid phase rate is about 56%.When the heat flux density of the collector plate is adjusted to350W/m~2,the average temperature difference between the laboratory and the comparison room is 3.3℃,the liquid phase ratio of the PCM is 56%～67%;when the heat flux density of the collector plate is 250W/m~2,The average temperature difference between the experimental room and the comparison room is 2.2℃,the liquid phase ratio is 44%～56%,and the heat flux density of the collector plate increases by 50W/m~2,the average temperature of the laboratory room increases by about 0.5℃.(3)In order to solve the problem of low thermal conductivity of PCM,copper foam can be used to enhance the heat transfer characteristics of PCM,and the phase change heat storage process of composite PCM was simulated.The results show that after the equivalent thermal conductivity of the heat storage body changes to 2W/(m·K)and3W/(m·K),the internal temperature distribution of the heat storage plate is more uniform,and the liquid phase rate increases to 91.86%and 95.37%,increasing the thermal conductivity of the PCM can effectively improve the heat storage performance and the utilization rate of the PCM. |
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