Development of Heat Pipe Modeling Capabilities in a Fully-Implicit Solution Framework

Abstract

AbstractOne key aspect in analysis of heat pipe microreactors is the efficient modeling of heat pipes and its coupling with the solid reactor core. Various options exist for modeling of heat pipes. Most models require an explicit coupling between the vapor core, which brings in an additional layer of coupling when the heat pipe model is integrated into a system-level safety analysis model. This additional layer of coupling causes both convergence concern and computational burden in practice. This article aims at developing a new heat pipe modeling algorithm, where the heat pipe wall, wick, and vapor core are discretized and coupled in a monolithic fully-implicit manner. The vapor core will be modeled as a one-dimensional compressible flow with the capability of predicting sonic limit inherently; a two-dimensional axisymmetric heat conduction model will be used to model the heat pipe wall and wick region. The heat pipe wick and vapor core are coupled through a conjugate heat transfer interface. Eventually, the coupled system will be solved using the Jacobian-Free Newton-Krylov (JFNK) method. It is demonstrated that the new coupled system works well. Consideration of the vapor compressibility in the two-equation model allows more detailed representation of the vapor core dynamics while remains light-weight in terms of computational complexity. The new model is verified by an approximate analytical solution to the heat pipe vapor core and is validated by a sodium heat pipe experiment.