Flow and heat transfer of He-Xe mixture in different ultra-compact heat exchangers

The helium-xenon gas-cooled space reactor is an ideal power system to overcome the power limitations of deep space exploration. The development of ultra-high performance heat exchangers is critical for such gas-cooled reactors, primarily due to the inherently low thermal conductivity of gases. This study compared the performance of four different heat exchanger configurations in helium-xenon applications was carried out using thermal performance, pressure drop, and compactness as heat exchanger evaluation indexes. The heat exchangers included gyroid heat exchanger, PCHE, HHE and CHE. Gyroid structures were first used in helium-xenon gas-cooled reactors. The effects of structural variations and Reynolds number on both hydraulic and thermal performance have been thoroughly investigated using CFD methods. The hydraulic diameters of the four heat exchangers were kept the same in the calculations and the range of Reynolds numbers was varied. It has been shown that the heat exchanger with a gyroid structure can improve the overall thermal performance by 10–78 %. The Nusselt number is increased by 40 % compared to the PCHE and by 300 % compared to the other two structures for a given pumping capacity. Gyroid structures form curved surfaces in space that increase turbulent kinetic energy compared to CHE and HHE. The average curvature of the surfaces is zero, making the surfaces smooth and continuous. And there is no flow dead zone compared to PCHE. Gyroid has the highest specific surface area and SPD. Due to its high specific heat transfer area and power density, the Gyroid-based heat exchanger shows significant potential for improving the cycle efficiency and compactness of space power systems.