Experimental And Numerical Simulation Of Enhanced Heat Transfer In Molten Salt Phase Change Process

As a phase change thermal storage material,molten salt has the advantages of large heat capacity,wide temperature range and strong thermal stability,which is widely used in the field of latent heat storage.However,there are many problems in phase change material,such as low thermal conductivity and short service life,which are not conducive to the stable and efficient operation of the thermal storage system.In this paper,molten salt is taken as the research object,experiment and numerical simulation of heat transfer enhancement technology in the molten salt phase change process are carried out,which provides some reference for the optimization design of the molten salt phase change heat storage system.The main work is as follows:1.The thermal conductivity test and molten salt heat storage experiment platform were set up.The results show that the thermal conductivity of the composite phase change material is 3-5 times of the pure nitrate.The temperature distribution of the molten salt in the horizontal section of the regenerator under different working conditions was obtained in the phase change heat storage experiment.The complete heat storage time of each working condition was compared and analyzed,which provides the experimental data reference for subsequent numerical simulation work.2.The numerical model of molten salt transformation was established,and the physical model was verified by the experimental results.The thermal storage characteristics of molten salt in different porosity and insertion filling conditions of foam metal were obtained by numerical simulation.The velocity cloud diagram,liquid phase ratio and temperature cloud chart of molten salt storage process in the container were analyzed.By comparing the temperature difference curves of each section,it was found that the heat storage rate of molten salt increases significantly after filling the foam metal.3.The heat transfer enhancement performance of fin tube and corrugated tube structure of the phase change heat storage unit was studied.The fin structure with the shortest heat storage time was obtained by orthogonal optimization method.The thermal storage characteristics of molten salt under multi structure were analyzed.Taking the thermal energy storage as the evaluation index of the storage/heat release performance,the optimal thermal storage unit structure was obtained.4.The heat transfer enhancement effect of foam metal and fin structure in horizontal casing heat storage unit was explored.The results show that the structural parameters,types,filling positions of foam metals and finned structures could enhance the heat conduction of molten salt.The comprehensive heat storage/release performance of each working condition was analyzed by the thermal energy storage evaluation index.