一种简化的高温热管启动模型

A Simplified Model for High-temperature Heat Pipe Startup

热管堆具有体积小、结构紧凑、功率密度高和固有安全性好等优点,被认为是深空和深海任务中最有前途的候选之一。为了研究其启动特性,建立兼顾计算精度及求解效率的热管启动模型至关重要。本文在充分考虑吸液芯区工质的熔化及气液界面处的蒸发和冷凝现象的基础上,建立了基于二维导热的热管壁和吸液芯区热阻网络模型。对于蒸汽区,基于尘气模型(DGM),研究分析了两种不同模拟方式的求解精度和计算效率。通过对不同碱金属热管实验的模拟,验证了模型的准确性。结果表明,模型能较好地模拟高温热管的启动特性,简化的等效热阻模型具有更高的计算效率,其更适合于热管堆系统的启动特性模拟。

Heat pipe cooled reactors(HPRs)have been considered as one of the most promising candidates for deep space and deep-sea missions due to their advantages of simple structure,high power density and high reliability,etc.To investigate the transient characteristics of such heat pipe cooled reactors,including startup,shutdown,power transients and accident conditions,it is necessary to develop suitable and efficient models for describing the core,the heat pipe and the power conversion system.Especially,for the startup process,an accurate and efficient model for the simulation of high-temperature heat pipe startup from the frozen state is indispensable.In this study,two transient models based on the dusty gas model(DGM)were developed.The first model(model 1)solved the mass and momentum equations of vapor flow,while the second model(model 2)simplified the vapor flow as a 1D steady-state heat conduction problem using an equivalent network model.The models considered the evaporation/condensation flux at the vapor/liquid interface using the kinetic theory of gases.The wick and wall were modeled using an improved network model,which took into account the phase transition of the working fluid in the wick.Different methods were used to solve these models in this paper.For the model considering the vapor flow,the finite-difference discretization scheme and the SIMPLEC algorithm were used to solve the governing equations.For the equivalent network model,a loosely coupled numerical method is employed.The solution of wick and wall equations was in a transient state,while the equivalent heat conduction equation of the vapor flow was solved in a steady state mode.The alternating direction implicit(ADI)was adopted to solve the equations for the wick and wall regions.The startup experiments of high-temperature heat pipes with different working fluids are simulated to validate the accuracy of these models.The results indicate that the simulation results agree well with the experimental data.Compared with the flat-front startup model,the temperature distribution calculated by model 2 is more accurate,and the description of startup is more plausible.Meanwhile,model 2 gives quite reasonable results although it is less accurate than the model 1.The calculation efficiency of the model 2 is significantly improved compared to model 1.Consequently,in the feasibility study stage of an HPR system,the simplified equivalent network model(model 2)with considering both accuracy and efficiency is suitable for the simulation of heat pipe startup.