Influence of internal heat generation on heat transfer in an MSR heat exchanger under laminar flow condition

A prominent feature of Molten Salt Reactor (MSR) is that the Internal Heat Generation (IHG) occurs within the fluid, as the nuclear fuel is dissolved in the coolant. This renders the energy equation non-homogeneous, requiring different mathematical approach. However, studies that quantitatively analyze the influence of IHG are limited. Especially, in the heat exchanger the IHG occurs coincide with wall cooling. Therefore, we analyzed the influence of IHG on a laminar pipe under wall cooling condition. Based on the superposition principle, the original problem is decomposed into two simpler boundary-layer sub-problems. The presence of IHG increased heat transfer rate and its influence increased with the magnitude of the IHG. Under uniform wall temperature condition, after sufficient flow development, the fluid temperature becomes constant exhibiting a conduction-like behavior, whereas under uniform heat flux condition, the fluid temperature increased despite heat transfer to the wall, superficially resembling a reverse heat transfer. Using the calculated data, the new heat transfer correlations were developed to incorporates the influence of IHG. The correlations were then applied to performance evaluations of MSR heat exchangers. It concludes that neglecting the IHG could lead to an underestimation of total heat transfer rate by up to 26 %. The findings offer a quantitative basis for considering IHG impact in future MSR heat exchanger design.