Large-eddy simulation of turbulent flow and heat transfer of helically corrugated tubes in the intermediate heat exchanger of a very-high-temperature gas-cooled reactor

The intermediate heat exchanger (IHX) is a vital component of very-high-temperature gas-cooled reactors (VHTRs) utilized for thermal applications of nuclear energy, specifically for hydrogen production. Enhancing the heat transmission capacity of IHXs is essential to provide sufficient heat for thermal processes. This study uses large eddy simulations to investigate IHX models consisting of both a smooth circular tube and helically corrugated tubes with five different geometric parametrizations. The results show how turbulent flow and heat transfer depend on the geometric parameters. Based on theories such as boundary layer theory, field synergy, and extreme dissipation, the characteristics of boundary layer separation, secondary flow, turbulent transport, field synergy, and dissipation characteristics in helically corrugated tubes are quantitatively analyzed. The study also investigates enhanced heat transfer mechanisms within the helically corrugated tubes, and the results attribute the enhanced heat transfer in helically corrugated tubes to the helical structure, which hinders the development of a fluid boundary layer, strengthens the intensity of secondary flow and turbulent transport, improves the synergy between the fluid velocity field and the temperature gradient, and reduces the thermal potential energy loss during the fluid heat transfer.