Experimental Study on Heat Transfer to Upward Flow of Supercritical Water in a 1-M Vertical Bare Tube

Abstract

Current water-cooled Nuclear Power Plants (NPPs) have relatively low thermal efficiencies (between 30‒38%) compared to those of thermal power plants such as SuperCritical Pressure (SCP) coal-fired (up to 55%). Based on proven power industry experience, it was proposed to design SuperCritical Water-cooled Reactors (SCWRs) with thermal efficiencies closer to modern thermal power plants. To aid in the design of these reactors, experiments with bare tubes of short heated lengths and small diameters are required. The current paper analyses experimental data obtained in a short 1-m vertical bare tube of 10-mm diameter, cooled with upward SCW flow at lower (G~200 kg/m²s) mass fluxes. The main emphasis is on the various regimes of HT (Normal (NHT), Improved (IHT), and Deteriorated (DHT)), within possible conditions of future SCWRs and SCW SMRs. The analyses indicate that current HT correlations are not able to accurately predict HT coefficients and wall temperatures under the analysed conditions.