Numerical investigation of flow reverser effects on thermal and hydraulic performance of a rotating horizontal spiral coil heat exchanger

This study numerically investigates a rotating horizontal spiral tube heat exchanger with integral flow-reversal segments designed to enhance thermohydraulic performance. As opposed to the typical spiral coil heat exchanger where the effect of Dean vortices gradually diminishes along the flow direction, an innovative configuration is introduced here where the motion of the Dean vortices can be re-created periodically through flow reversal. Three-dimensional computational fluid dynamics analysis was carried out using the concept of rotating reference frame to examine the fluid flow and heat transfer properties for the range of Reynolds number 2000 to 6000, which corresponds to the laminar to transitional flows in curved tubes. It was found that, relative to a conventional horizontal spiral coil, there is an improvement in Nusselt number of 16.3%, 26.8%, and 32.9% at Reynolds numbers of 2000, 4000, and 6000, respectively. The pressure drop penalty is about 6.7%, 17.9%, and 12.6% at Reynolds numbers of 2000, 4000, and 6000, respectively. These results demonstrate that geometric modification through periodic flow reversal can significantly enhance heat transfer without the need for internal inserts. The proposed configuration provides an efficient, manufacturable, and energy-efficient solution for industrial applications such as desalination, cooling, and waste heat recovery.