Study On The Characteristics Of Molten Salt Heat Storage Process Based On Fluid-Structure Two-way Coupling

With the large-scale application of molten salt heat storage,it is of great significance to improve the heat storage and release efficiency of molten salt.The fluid-induced vibration-enhanced heat transfer technology provides a new idea for enhancing liquid molten salt sensible heat storage.In this paper,the molten salt heat storage process is taken as the research object,using numerical simulation methods and experimental research methods,the structure of the double helical tube bundle element that can achieve fluid-induced vibration is presented,Its characteristics of vibration,heat transfer and fatigue strength in the process of molten salt heat storage are analyzed.The research results provide reference for the application of spiral tube bundle vibration elements in the process of molten salt heat storage enhancement.The main research work is summarized as follows:1.Based on the fluid-induced vibration theory,combined with the basic characteristics of the molten salt heat storage process,vibration elements with double spiral tube bundle structure and triple spiral tube bundle structure were proposed.By comparing the vibration characteristics of the two under different fluid-inducing conditions,it is found that the application of pulsating flow in the tube will produce double-helical tube bundle a better vibration effect.2.Combining finite element analysis and experimental research to analyze the natural vibration characteristics of the double spiral tube bundle,the natural frequency and vibration mode of the tube bundle are obtained.The numerical calculation method of fluid-solid two-way coupling was used to study the influence of pulsating flow parameters,molten salt's flow velocity and temperature outside the tube on the vibration characteristics of the tube bundle.An orthogonal test plan is designed to analyze the vibration characteristics of the double spiral tube bundle with different structural parameters.3.Establishing an element vibration model of bundle to analyze the mechanism of vibration-enhanced heat transfer,obtaining the changing law of surface heat transfer coefficient with amplitude,frequency and vibration direction of tube wall,and the vibration-enhanced heat transfer characteristics at different molten salt flow rates are also studied.The research on the overall heat transfer performance of the double spiral tube bundle vibration element found that when the flow rate of molten salt is low,the vibration of the double spiral tube bundle induced by pulsating flow can increase the heat transfer intensity by 1.5 times.4.The dangerous location of the tube bundle is determine by the force analysis of the double spiral tube bundle in a vibration period.Based on the Von Mises equivalent stress criterion for multi-axis fatigue analysis,it is obtained that the safety factor need meet J?1.8 to avoid fatigue damage of tube bundle.In addition,the effects of pulsating flow frequency,pulsating amplitude and tube bundle structure parameters on fatigue strength are studied,and a fluid-induced vibration scheme that can not only enhance heat transfer but also prevent tube bundle damage is concluded.