Research On Heat Storage And Release Performance Of Phase Change Heat Storage And Heating Device Based On Spherical Package

With the rapid development of social economy,the shortage of energy supply and environmental pollution have become social problems all over the world.The use of clean energy such as solar energy to replace non-renewable energy sources can alleviate energy shortages and environmental pollution.The development and use of solar energy must solve its intermittent and unreliable problems.PCM is a kind of heat storage material with potential heat storage capacity.It has a large heat storage density and a constant temperature for heat storage and release.It is encapsulated and combined with the original water tank to form a composite phase change hot water storage tank,which can increase Heat storage can extend the heating time,and its application to solar heating systems can obviously solve the problem of intermittent and unreliable solar energy.Therefore,how to improve the heat storage performance of heat storage devices has become a research focus in the field of solar heating.In this paper,the composite inorganic salt calcium chloride is used as PCM,encapsulated in a smooth spherical phase change unit.In order to avoid the appearance of PCM phase change "dead zone",the traditional heat storage device was improved,and a new type of ball type phase change heat storage device with a lower inlet and upper outlet water flow method and a partition plate inside was designed and the performance was built.The test platform was used to test its heat storage and release performance under various working conditions,and obtained the curves of PCM temperature and HTF temperature with time of different layers of heat storage balls in the water tank during the heat storage and release process.The structure of the inlet and outlet and the addition of the partition plate make the temperature distribution in the water tank more uniform during its heat storage process;the temperature in the heat storage device is better stratified during the heat release process,ensuring that the hot water source continuously flows out from the outlet.In addition,the heat storage time of the hot water storage tank with different inlet water temperature and inlet water flow rate was obtained,and it was found that the heat storage time of the hot water storage tank continuously decreased with the increase of inlet water temperature and inlet water flow rate.By testing the constant inlet temperature and the variable inlet temperature in the hot water storage tank during the heat release process,it was found that the variable inlet temperature reduced the temperature difference between the HTF and the PCM compared to the constant inlet temperature Latent heat release time of PCM,thereby improving the heat release performance of the hot water storage tank.In order to further improve the heat storage and release performance of the heat storage device,a spiral groove heat storage ball with the same volume as the smooth heat storage ball is designed in this paper.The surface ratio of the groove ball is increased by 32.65%.The distribution method is the same,and they are evenly distributed in the phase change heat storage device.In order to understand the heat storage and release process inside the heat storage device,physical models and mathematical models are established for the two types of heat storage devices.The heat storage and release process of the two heat storage devices under the same working conditions has been numerically simulated.Through the analysis of the phase change process and the fluid velocity field of the heat storage ball and the whole heat storage ball in the two heat storage devices,it was found that the spiral groove on the surface of the groove ball changed the flow state of the fluid and increased the heat storage tank.Disturbance of the fluid,there are many turbulent areas,which enhances convection heat transfer to a certain extent,improves the heat exchange efficiency,and improves the overall heat storage and release efficiency for the entire heat storage tank;The pressure of the device is analyzed,and the internal fluid pressure drop is relatively small and belongs to a small pressure drop.The impact of the mechanical energy of the fluid loss can be ignored.This paper explores a new type of phase-change heat storage device with a combination of experiment and simulation,which provides reference value for the optimization and engineering application of the heat storage device in the future,and helps energy conservation and environmental protection.