Development of a conduction-based model for analyzing frozen startup of alkali-metal heat pipes

Abstract

This study presents a conduction-based heat pipe modeling approach to simulate the transient thermal response of liquid metal heat pipes (LMHPs) during frozen startup. By formulating the model solely on the heat conduction equation, the approach offers a simplified yet physically grounded framework that avoids the complexities associated with detailed multiphase flow modeling. The model incorporates effective thermal conductivity of the metal vapor to represent evolving vapor flow regimes and employs a loosely coupled numerical scheme to address the disparity in time scales between vapor dynamics and wall conduction. Implemented in commercial computational fluid dynamics (CFD) software, the model was validated against experimental data from sodium heat-pipe startup tests. The results demonstrate good agreement across different heat pipe configurations and heat inputs, confirming the model's capability to capture key thermal transient behaviors during frozen startup. Owing to its simplicity, robustness, and ease of implementation, the proposed model offers practical value for both academic research and engineering applications involving LMHP technologies.