This work demonstrates several modeling approaches of thermal fluids phenomena in heat pipes and the thermal coupling of the heat pipe to a graphite monolithic block in a microreactor context, taking into account the presence of a gap between the two. We show that the selection of the heat pipe model has a significant impact on the transient behavior of a 3D, coupled microreactor assembly problem by comparing results obtained using different heat pipe models from the heat pipe code Sockeye. Additionally, we show that the choice of coupling strategy has significant consequences for both accuracy and performance. Our recommendation based on these studies is to employ a heat flux coupling strategy instead of a temperature coupling strategy, in a loosely coupled fashion for steady state calculations and tight coupling or operator splitting for transient scenarios. Although this research is numerical in nature and does not include validation cases, it provides important insights in the modeling of thermal fluids phenomena in heat pipe microreactors.
