压力容器外部冷却沸腾临界过程数值模拟研究

Numerical Simulation Research on Boiling Critical Process in External Cooling of Pressure Vessel

针对压力容器外部冷却条件,基于CFD商业软件并通过编写用户自定义函数(User-Defined Function,UDF)对环形冷却剂流道内沸腾相变及临界过程进行了数值模拟,研究了沸腾两相流动的压力场、速度场、相分布以及温度场分布特性,并对偏离泡核沸腾(Departure from nucleate boiling,DNB)型临界过程进行了定性分析。模拟结果表明:沿加热壁面至绝热壁面存在压力梯度;加热壁面附近的速度大于绝热壁面附近的速度;随流道高度增加,由于流道的弧形结构导致汽相在浮升力作用下逐渐向流道加热壁面积聚,在特定工况下,流道壁面温度明显上升,发生沸腾临界现象。

Aiming at the external cooling condition of pressure vessel,the boiling phase transition and critical process in annular coolant passage were simulated by using CFD business software and writing user-defined function(UDF),studies the characteristics of pressure field,velocity field,phase distribution and temperature field distribution of boiling two-phase flow,and conducts qualitative analysis of departure from nucleate boil ing(DNB)critical process.The simulated results showed that there was a pressure gradient along heated wall to adiabatic wall;the velocity near heated wall was greater than that near adiabatic wall;as the height of the chan nel increased,due to the curved structure of the flow passage,the vapor phase gradually accumulated to the heated wall under the action of floating lift.Under certain conditions,the temperature of the wall increased abruptly and indicated the boiling crisis happening.