Numerical models to predict steady and unsteady thermal-hydraulic behaviour of supercritical water flow in circular tubes

• A CFD model and 1-D code THRUST are developed to simulate the supercritical water flows.
• The supercritical flows with the normal heat transfer and deteriorated heat transfer are simulated.
• The numerical results are compared with the experimental data and the errors are reported.
• The transient simulations are also carried out using the CFD and THRUST.
• The transient results obtained using the CFD and THRUST are compared under different conditions.

The present paper is aimed at the development of numerical models to predict steady and unsteady thermal-hydraulic behaviour of supercritical water flow at various operating conditions. A simple one-dimensional numerical thermal-hydraulic model based on a finite-difference scheme has been developed. A detailed CFD analysis based on two turbulence models, Reynolds Stress Model and k–ω SST model, has also been presented in this paper. Seven experimental cases of steady state and vertically up flowing supercritical water in circular tubes operated at various working regimes, such as normal and deteriorated heat transfer regions, are used to validate the numerical models. Comparisons for steady state flow show good agreement between the numerical and experimental results for all normal heat transfer cases and most of the deteriorated heat transfer cases. Next, the numerical models are used for transient simulations. Three case studies are undertaken with a purpose to quantify the time dependent responses from both the 1-D model and CFD model. The comparisons carried out for both the normal and deteriorated heat transfer conditions show a good agreement between the two numerical models.