Specifics of Heat Transfer to Supercritical Water Flowing Upward in Short Bare Tube

Abstract

Water-cooled nuclear power reactors, with thermal efficiencies ranging from 26-38%, lag behind combined-cycle thermal power plants. Enhancing the efficiency of next-gen Nuclear Power Plants (NPPs) is crucial. The conventional approach for water-cooled NPPs involves transitioning to supercritical pressures, a strategy employed in the thermal power industry over 60 years ago. Large- capacity SuperCritical Water-cooled Reactors (SCWRs) and SuperCritical Pressure Small Modular Reactors (SCP SMRs) are currently under development, necessitating a comprehensive understanding of heat transfer at supercritical pressures. Experimental data from short vertical bare tubes, conducted by Dr. V. Razumovskiy at the National Technical University of Ukraine, at 23.5 MPa pressure, mass fluxes 2193 kg/m²s and heat fluxes within 630-2602 kW/m². Reveals that while a subcritical-pressure heat-transfer correlation by Dittus and Boelter reasonably predicts normal heat-transfer regimes, it underestimates values in deteriorated heat-transfer regimes and pseudocritical regions.