Development of a transient numerical model for contact melting of molten material on a narrow plate component with varying contact thermal resistance

During a core meltdown, the contact melting of the crust of a molten pool against narrow plate components within the reactor exhibits characteristics of a complex convective boundary condition. This complexity arises because the early stage is governed by the coupling of contact thermal resistance and heat conduction mechanisms, while the melting phase is influenced by the overall system heat transfer behavior. Thus, accurately modeling this process poses significant challenges. To address this issue, this paper establishes a transient numerical model to simulate the contact melting behavior between a heat source and a narrow plate of phase change material (PCM), based on contact melting theory. The governing equations are coupled with the heat conduction differential equations of both the heat source and the PCM, with full consideration of the role of contact thermal resistance during the conduction stage. This coupled approach avoids traditional strong numerical coupling computations, significantly reducing computational costs. The results demonstrate that the model effectively tracks the dynamic evolution of the melting rate. Furthermore, the study reveals that modifying the contact thermal resistance by introducing a eutectic reaction substantially improves the prediction accuracy of the melting initiation time, highlighting the importance of considering the influence of the eutectic reaction on contact thermal resistance in the model, which plays a key role in enhancing model accuracy.