Research On Operation Performance Of Molten Salt Heat Storage System Based On Fluid-structure Coupling Method

To effectively solve the energy sustainability problem,concentrated solar power（CSP）has been proposed and utilized.As an important renewable energy,CSP can meet the strategic goals of"double-carbon"objective proposed by China,and has important practical meaning.However,solar thermal power generation is subject to the fluctuation of solar radiation and low power generation quality.To solve the volatility problem of solar energy,energy storage systems are needed,and single-tank systems can reduce the CSP cost within a certain range.Hence,it is meaningful to conduct relevant studies on single-tank systems for the sustainable development of CSP.Based on the fluid-structure calculation method,this study conducts the operating simulation research of thermoclinic thermal energy storage（TTES）tank using solid porous medium and ternary nitrate salt.The effects of different parameters on the operating performance and mechanical characteristics of the ternary nitrate salt TTES tank are analyzed.The evaluated parameters include the inlet molten salt flow rate,initial cold salt temperature,inlet hot salt temperature,porosity,equivalent diameter,thermal conductivity and specific heat capacity of the porous medium（PM）.The main contents and results are concluded as below:First of all,the numerical model of the ternary nitrate salt TTES tank is built and validated.Under the fixed parameter condition,the operating process of the ternary nitrate salt TTES tank is simulated,revealing the operating stability of the tank.The analysis results indicate that the heat storage time of the tank is about 5.33 h,the peak heat storage and release powers of the tank are both about 1.92×10¹⁰k J/h,the effective heat storage is 6.04×10¹⁰k J,the effective heat release is 5.70×10¹⁰k J,and the discharge efficiency is 94.4%.The maximum axial mechanical stress of the tank wall is 131.7 MPa.The standby analysis results demonstrate that during the standby time of 0～24 h,the stability of the ternary nitrate salt TTES tank is relatively good,and the rapid diffusion of the thermocline did not happen.After that,the effects of seven parameters on the operating performance of the ternary nitrate salt TTES tank are analyzed.The results show that the thermoclinic thicknesses in the heat storage and release processes are inversely proportional to the inlet salt flow rate,initial cold salt temperature and specific heat capacity of the PM,and are directly proportional to the inlet hot salt temperature,equivalent diameter and heat conductivity of the PM.The PM porosity has no effect on the thermoclinic thickness.The heat storage and release durations are inversely proportional to the salt flow rate,directly proportional to the porosity and specific heat capacity of the PM,and are basically not affected by the other four parameters.The effective heat storage and release quantities of the ternary nitrate salt TTES tank can be risen by properly reducing the salt flow rate,initial cold salt temperature,equivalent diameter and heat conductivity of the PM,or by properly increasing the initial hot salt temperature,porosity and specific heat capacity of the PM.Finally,the impacts of typical parameters on the mechanics characteristics of the ternary nitrate salt TTES tank are analyzed.The results indicate that the mechanical stress of the tank wall is inversely proportional to the salt flow rate and initial cold salt temperature,and directly proportional to the inlet hot salt temperature,porosity,equivalent diameter,heat conductivity and specific heat capacity of the PM.When the TTES tank is designed,the key parameters should be selected on the premise of combining the heat storage and release requirements with the safety of the tank wall structure.