Geometry optimization for supercritical water heat transfer enhancement in non-uniformly heated rifled tubes

Abstract Optimization of geometric parameters for rifled tube is of great importance for safe operation of heat exchangers. In this paper, the influences of geometry, including rib height, pitch and rib shape, on the heat transfer performance of supercritical water in circumferentially non-uniformly heated rifled tubes were comprehensively studied. The differences of geometry effects on heat transfers in rifled tubes under uniform heating and non-uniform heating conditions were compared. The impact extent of geometry changes for forced convection and mixed convection heat transfer conditions were obtained by conducting simulations under relatively low q/G and high q/G conditions respectively. Finally, the mechanism of heat transfer enhancement resulting from the changes of geometric parameters was revealed. The results show that different geometric parameters have different influences on the overall heat transfer performance of supercritical water in rifled tubes. There exists an optimum value for rib height. According to the analysis, the optimum rib height is 0.45 mm for the present study. Heat transfer is enhanced with the decrease of pitch and the influence of rib shape is negligible. The changes of geometric parameters, which can improve the turbulence intensity in the boundary layer range of 30