成核密度模型对弧形表面CHF的影响

Effect of Nucleation Density Model on CHF of Curved Surface

反应堆发生严重事故时,必须及时对反应堆压力容器(RPV)下封头进行外部冷却以降低下封头损毁可能性,事故期间下封头具有很高的热流分布,在实施外部冷却时可能出现由于过冷沸腾导致的气泡聚集而产生换热恶化从而烧毁。本研究利用ANSYS Fluent软件进行RPV外部冷却的临界热流密度(CHF)数值计算,并通过实验对比发现Basu Warrier和Dhir研究的成核密度模型可以很好地应用于球形表面CHF计算。通过对比球形和椭球形下封头CHF,认为椭球形下封头的CHF特性与球形结构完全不同,并不能用球形结构的实验和计算结果去推测椭球形结构的数值和变化规律。

In the event of a serious accident,external cooling can be applied to the lower head of the reactor pressure vessel(RPV)in order to reduce the possibility of damage to the lower head.However,there will be great heat flow surrounding the lower head of the RPV,so external cooling may cause subcooled boiling,which gathers bubbles and deteriorates heat exchange,even burns out.This research uses ANSYS Fluent to calculate the critical heat flux(CHF)for external cooling of the RPV,and it is found that the nucleation density model studied by Basu Warrier and Dhir can be well applied to the calculation of CHF on the spherical surface.By comparing the CHF of the spherical and ellipsoidal lower head,it is believed that the CHF characteristics of the ellipsoidal lower head are completely different from the spherical structure.The experimental and calculation results of the spherical structure cannot be used to infer the numerical value and variation of the ellipsoidal structure.