交变热流与腐蚀作用下的太阳能吸热器传热特性及热应力调控机制

Thermal stress failure of solar power tower molten salt receiver caused by alternating temperature and corrosion increasingly paid more and more attention. The objective orientation of the project is to reveal thermal stress regulation mechanism of molten salt receiver with coupling effects of non-uniform time varying heat flux field and pitting corrosion, and then to focus on the correlation mechanism of receiver thermal stress and coupling effect of alternating heat flux and molten salt corrosion as the key scientific question. The heat transfer characteristics as well as thermal stress occurrence and distribution rule of receiver with pitting corrosion defect are analyzed. Under thermal cycle conditions, corrosion kinetics experiments are conducted to analyze the influence mechanism of Cl- concentration and thermal cycle alternative frequency on corrosion of heat pipe material. The corrosion morphology characterization method of the receiver for different years are also provided. Based on the feature of corrosion morphology and alternating thermal environment, multi-scale coupling model of optics, thermal physics and mechanics with corrosion defect is built. The temperature field and stress distribution of receiver under different operating parameters and structural parameters are studied. High efficiency and precision numerical solution strategies of the receiver structural fracture behavior prediction are formed. Ultimately, dynamic critical heat flux estimation method and thermal stress release mechanism of the receiver are developed. The project is to establish the internal relationship between heat flux and stress strength on the receiver surface and lay a theoretical foundation for exploring control method of the molten salt receiver thermal stress.

塔式太阳能熔盐吸热器在交变热流和腐蚀下所产生的热应力失效问题，日益受到广泛关注。本项目以非均匀时变热流和点蚀腐蚀耦合作用下的熔盐吸热器热应力调控机制为目标导向，紧密围绕交变热流和熔盐腐蚀耦合作用与吸热器热应力场的关联机制这一关键科学问题，剖析存在点蚀腐蚀缺陷下的吸热器传热特性以及热应力发生与分布规律；通过热循环条件下的腐蚀动力学实验，分析氯离子浓度、热循环交变频率对吸热管材作用的腐蚀机理，提出不同年限下吸热器腐蚀形貌的表征方法；基于腐蚀形貌演化规律和热环境交变机制，构建含有腐蚀缺陷下的光-热-力多尺度耦合模型，研究不同运行参数和结构参数下吸热器温度场和应力特性分布规律；针对吸热器，形成其结构断裂行为预测的高效高精度数值求解策略，最终发展出吸热器动态临界热流密度的合理预估方法和热应力调控机制。本项目构建出吸热器表面热流密度和应力强度的内在关联，为探究熔盐吸热器热应力失效调控方法提供理论依据。

塔式太阳能熔盐吸热器在交变热流和腐蚀下所产生的热应力失效问题，日益受到广泛关注。本项目以非均匀时变热流和点蚀腐蚀耦合作用下的熔盐吸热管热应力调控机制为目标导向，紧密围绕交变热流和熔盐腐蚀耦合作用与吸热管热应力场的关联机制这一关键科学问题，剖析存在点蚀腐蚀缺陷下的吸热管传热特性以及热应力发生与分布规律。通过构建非均匀时变热流下熔盐吸热管的光-热-力多尺度耦合模型，分析归纳吸热管表面热流分布、熔盐流速以及吸热管内径对完整吸热管温度场和热应力特性分布规律，得到热流密度是影响完整吸热管最大热应力的关键因素，最大热应力往往发生在吸热面外壁的两侧位置上；基于腐蚀形貌演化规律和热环境交变机制，剖析存在点蚀腐蚀缺陷下的吸热管温度场以及热应力场发生与分布规律，得到相对于完整吸热管，腐蚀缺陷条件下吸热管最大热应力有所增加，最大热应力位置变为腐蚀坑附近，随着球形腐蚀半径增大，吸热管最大热应力显著增加，此时腐蚀坑附近热应力场是温度梯度和腐蚀坑自身结构应力集中共同作用的结果；运用雨流计数法和疲劳累积损伤理论，对吸热管寿命进行预测，通过建立不同腐蚀半径条件下吸热管表面最大允许热流密度与年累计损伤之间的关系曲线，最终发展出随腐蚀半径变化的吸热管动态临界热流密度合理预估方法和热应力调控机制。本项目构建出吸热管表面热流密度和热应力强度的内在关联，为探究熔盐吸热管热应力失效调控方法提供理论依据。