The primary objective of this work is to numerically study the effect of system pressure on the occurrence of dryout phenomena in heap-shaped, heat-generating porous debris beds. This is achieved using a multiphase computational fluid dynamics (CFD) model that is implemented in the framework of the commercial CFD platform ANSYS FLUENT. The model is extensively validated with available experimental data on two different aspects: pressure drop in two-phase flow through porous media and prediction of dryout in typical porous debris beds. A wide range of system pressure, relevant to severe accident conditions, is considered in this analysis in order to obtain a thorough understanding of its impact on multiphase flow and dryout occurrence in porous debris beds. This analysis is performed for different subcoolings of flooding water, which gives additional knowledge on the effects of coolant subcooling on dryout occurrence. Results indicate that dryout in debris beds occurs at progressively higher power densities as the system pressure is raised. Similar effects are observed with increase in liquid subcooling as well.

这项工作的主要目的是从数值上研究系统压力对堆状热生质多孔碎屑床中变干现象的影响。这可以通过在商用CFD平台ANSYS FLUENT框架中实现的多相计算流体动力学（CFD）模型来实现。该模型已通过两个方面的可用实验数据进行了广泛验证：两相流经多孔介质的压降和典型多孔碎屑床中的变干预测。在此分析中，考虑了与严重事故情况相关的大范围系统压力，以便全面了解其对多孔碎屑床中多相流和变干现象的影响。此分析是针对不同的过冷水进行的，这提供了有关冷却剂过冷对干燥发生的影响的更多知识。结果表明，随着系统压力的升高，碎屑床中的变干发生在功率密度逐渐升高的情况下。随着液体过冷度的增加，也观察到类似的效果。