Heat Transfer And Thermal Stress Analysis Of Molten Salt Storage Tank Preheating Process For Solar Thermal Plants

Solar thermal power technology has the advantages of high energy density,easy heat storage and good grid compatibility,which can achieve all-weather continuous power generation.The molten salt storage tank is a key component in the thermal storage system,to reduce the thermal shock and thermal stress on the tank when filling it,preheating is necessary to ensure the safe operation of the thermal storage system of the solar thermal power plant.Therefore,this paper took a molten salt storage tank in the solar thermal power plant as the research object,and studied the preheating process of the molten salt storage tank based on CFD method,to explore the influence on the preheating time,the temperature distribution and thermal stress of the tank during the preheating process.In this paper,the geometric model of the tank was constructed by Pro/E according to the geometric size of the actual one,and the unsteady heat transfer model of the preheating process of the tank was established based on the CFD method.The accuracy and feasibility of the tank calculation model were verified by comparing the simulation results with the actual engineering data of the tank average temperature,maximum temperature and minimum temperature with heating time.Based on the heat transfer model established in this paper,the temperature distribution of the molten salt storage tank during the stepped preheating process was studied,and the influence of parameters such as preheating gas,temperature end difference,inlet mass flowrate,injection angle and tank size on the preheating time was analyzed.The results show that,with the progress of the preheating process,the temperature of the tank rose more and more slowly,the maximum temperature difference gradually decreased,and the temperature at the edge of the junction between the bottom plate and the side wall of the tank was the lowest.Increasing the temperature end difference can significantly decreased the preheating time of the tank,when the gas mass flow was 2.7kg/s,the temperature end difference increases by 100%,and the heating time was deceased by about 76%.Increasing the mass flow of preheated gas can significantly shorten the preheating time of the tank,when the temperature end difference was150 ℃,the gas mass flow increases by 100%,and the heating time was shortened by about57%.Changing the circumferential or vertical angle of the preheating gas injection has little effect on the preheating time of the tank.Increasing the inner diameter of the storage tank increased the preheating time,and when the inner diameter of the storage tank added by about57%,the preheating time increased by about 380%.Based on the temperature distribution data calculated by the heat transfer model,the thermal stress of the storage tank under different inlet flow rates and different inlet temperatures is calculated and analyzed.The results show that the increase of inlet flow and inlet temperature will increase the maximum thermal stress of the storage tank,and the impact of inlet temperature will be more significant.With the progress of the preheating process,the maximum stress of the tank is transferred from the tank top area to the connection between the tank wall and the tank bottom,and the preheating methods need to be improved for the stress concentration areas.