Heat transfer characteristics of supercritical water in a tube: Application for 2D and an experimental validation

Abstract

Heat transfer to water at supercritical pressures has been numerically investigated using a two-dimensional modeling approach. The simulations in a two-dimensional domain have been performed using the low-Reynolds k–ϵ turbulence model, and the IAPWS-IF97 formulation to describe the properties of water at different conditions.The accuracy of the model is validated using an experimental setup at supercritical pressures. The experimental dataset was obtained in supercritical water flowing upward in a 0.4m long vertical bare tube with 10mm ID. The temperature data were collected at multiple heights in the tube and at pressures of about 24MPa, an inlet temperature of 300°C, values of mass flux ranged from 6.6 to 10kg/m2s and an outer wall temperature of 300°C resulting in bulk-fluid temperatures exceeding the pseudo-critical temperature. The comparison of the temperature results shows a good agreement for low mass fluxes between the experimental and numerical data. At these low flow conditions, the 2D model predicts recirculation zones near the inlet which results in a more complex simulation. The accuracy of the 2D model for higher fluxes cannot be properly assessed on basis of the experimental data because of practical limitation of the setup. But the accuracy of the 2D model for the higher mass flow cases is expected to be even more accurate, due to less complexity in the flow calculation because of smaller buoyancy effects.Finally simulation results of the two-dimensional model at higher mass flows are compared with several frequently used one-dimensional correlations from literature for heat transfer at supercritical pressures.