非能动余热排出系统换热特性研究及相关湍流模型评价

Study on Heat Transfer Characteristics of the Passive Residual Heat Removal System and Evaluation of Relevant Turbulence Model

在全厂断电事故下,非能动核电厂的非能动余热排出热交换器(PRHRHX)将大多数的堆芯衰变热带出至内置换料水箱(IRWST),但PRHRHX属于大型非稳态热交换器,其传热机理十分复杂。为了弄清PRHR HX的换热特性,文章针对非能动堆芯冷却系统整体性能试验装置(ACME)上的PRHR系统,利用CFD方法开展数值计算,并与试验结果进行对比分析。结果发现:IRWST内沿垂直高度方向上存在明显的热分层现象,且温度沿径向方向趋于均匀分布。但SST湍流模型的计算结果要优于RNG k-ε模型,并与试验结果吻合良好;在IRWST底部区域,温度始终处于初始状态,在传热管下部水平段区域,温度上升较为明显,但高于该区域,温度上升又变得平缓,在传热管上部水平段区域,温度上升十分明显;在整个换热进程中,C型传热管的上部水平段带出了绝大部分的热量,而竖直段和下部水平段只带出了余下的少部分热量。

Under the station blackout accident, the passive residual heat removal heat exchanger(PRHR HX)in the passive nuclear power plant removes most of the core decay heat to the in-containment refueling water storage tank(IRWST),but the PRHR HX is a large unsteady heat exchanger,the heat transfer mechanism is very complicated. In order to understand the heat transfer characteristics of PRHR HX,this paper uses the CFD method to carry out numerical calculations for the PRHR system on the passive core cooling system performance validation facility,and the contrastive analysis with the test results was carried out. It is found that there is a significant thermal stratification phenomenon along the vertical height within the IRWST and the temperature tends to be uniformly distributed in the radial direction. However,the results of SST turbulence model are better than that of RNG k-ε model,which is in good agreement with the test results. In the bottom region of IRWST,the temperature is always in the initial state,and the temperature rise is obvious in the lower horizontal section of the heat transfer tubes,but above this region,the temperature rise has become flat again,in the upper horizontal section of the heat transfer tubes,the temperature rise is very obvious. Throughout the heat transfer process,the upper horizontal section of C-type heat transfer tubes bring out the most of heat,and vertical section and the lower horizontal section only bring out the remaining part of the heat.