熔盐储罐热分层混温过程研究

Research on thermal stratification and control process in molten salt storage tanks

储热系统是太阳能热发电系统的核心系统之一,在调试、大修以及连续较差气象条件下,储罐面临较长时间的停机,从而形成热分层现象,对储罐安全性造成影响。加大储罐内的扰动是破坏热分层现象的最有效手段,目前在储罐设计研究中对热分层现象破坏研究内容较少。通过流体动力学(CFD)模拟计算分析了熔盐储罐发生热分层现象后通过再循环扰动热分层被破坏现象。计算结果显示熔盐在储罐内部以100 kg/s流量再循环扰动时能够在2.8 h得到充分混合。在低温熔盐储罐采用分配环进行混温时,需要3.1 h,储罐内熔盐最大温差下降至14.5℃。因此可将此流量作为该项目实际运行阶段发生热分层现象后的再循环扰动流量。

Heat storage system is one of the core systems in a CSP plant.During the commissioning,overhaul or under continuous poor weather conditions,storage tanks will encounter long-period shutdowns,resulting in thermal stratification which will affect the storage tank security.Intensifying the disturbance in storage tanks is the most effective means to eliminating the thermal stratification phenomenon,but there is little research on this method in storage tank design.The thermal stratification elimination realized by recirculation disturbance after the formation of thermal stratification in molten salt storage tanks was analyzed by CFD simulation.The results show that the molten salt recirculating inside the tanks can be fully mixed in 2.8 h when it is disturbed by a 100 kg/s flow.In a cold tank with a circulation pipe,it takes 3.1 h for mixing,and the maximum temperature difference of the molten salt in the storage tank drops to 14.5℃.Therefore,this flow can be regarded as the recirculating disturbance flow after thermal stratification in the operation phase of the project.