跨临界泄压瞬态传热特性的模型敏感性分析

Sensitive Analysis of Heat Transfer Model During Trans-critical Depressurization

在停堆或失水等事故工况下,超临界水冷堆将经历跨临界泄压过程,系统压力从超临界状态降到拟临界点22.064MPa以下。而对于次临界区,临界点附近的临界热流密度值很低,极易发生沸腾临界,导致加热棒壁面温度迅速升高,因此跨临界泄压过程是超临界水冷堆失水事故安全分析的关键。目前,跨临界泄压瞬态过程可以通过系统程序进行计算,但依然缺乏有效的实验验证。故本文依托上海交通大学的超临界流体多功能实验回路(Supercritical WAter MUltiPurpose loop,SWAMUP)跨临界泄压过程的实验,利用德国核安全中心(GRS)开发的系统程序ATHLET3.0进行建模计算,分析跨临界泄压过程传热特性。通过调节次临界区临界热流密度、最小膜态沸腾温度、骤冷前沿模型等相关参数,对计算模型进行敏感性分析,为跨临界泄压瞬态过程的准确计算提供参考。计算结果表明,加热棒壁面是否发生温度飞升取决于所选用的临界热流密度和最小膜态沸腾温度的值;骤冷前沿模型的使用可以实现壁面再湿润,降低壁面温度。

During shutdown and loss of coolant accident conditions, Supercritieal Water Cooled Reactor （SCWR） will undergo a pressure decrease from supercritical to subcritical pressure. And critical heat flux is likely to occur even at relatively low heat flux near critical pressure. Then, the heating wall will sharply heat up which causes rapid temperature increase. Hence, trans-critical transient are of crucial importance for LOCA safety analysis. Although the process can be calculated by several system codes, a reliable validation work is not available for now. In order to analyze the heat transfer mechanism, the trans-critical transient of Supercritical Water MUltiPurpose loop （SWAMIIP） with 2X2 rod h,,nrll~ ;n ,qh^n~h~; 1;~,~ T,~n,, Ii＂n; ;＊,, （qTTl＂~＇~ l^o~ l,~o^simulated by ATHLET 3.0, which is a kind of system code developed by GRS. And the calculations with different heat transfer parameters such as critical heat flux, minimum film boiling temperature and quench front model were carried out. The calculation results indicate that whether the heating wall temperature will sharply increase depends on the value of critical heat flux and minimum film boiling temperature. And the quench front model can bring rewetting process to the hot wall. In the future, the heat transfer model and the criterion for rewetting phenomena near critical pressure should be developed.