Research on the conversion mechanism between cold and hot performance of reactor coolant pump based on entropy production theory

As the core equipment of PWR primary circuits, the reactor coolant pump (RCP) exhibits performance evaluation deviations due to property differences between high-temperature operation and room-temperature experimental conditions. Through full-flow-domain modeling integrated with entropy production theory and vortex dynamics-based multiscale analysis, the mechanism by which temperature variations affect flow losses in RCPs has been systematically elucidated. The study reveals that reduced dynamic viscosity under elevated temperatures diminishes the dominant role of velocity gradients in viscous dissipation. Entropy production concentration zones exhibit a strong correlation with high-speed shear flows. Vortex structure analysis identifies the hub-region counter-rotating vortex and inlet horseshoe vortex as primary contributors to energy losses in the impeller domain. The formation mechanism of high-intensity vorticity in the volute outlet section is directly attributed to the tongue-guide vane interference effect. Notably, the viscosity-dissipation suppression effect under high-temperature conditions significantly weakens local vortex structure generation intensity, resulting in a 0.51 % reduction in total system vorticity volume. Furthermore, the dominant low-frequency component at 0.33fn is confirmed to be vortex-induced, with its amplitude decreasing as temperature rises. These findings provide a theoretical foundation for optimizing flow fields and enhancing the hydraulic performance of RCPs under high-temperature operating conditions.