Simulation of the thermal field of submerged supercritical water jets at near-critical pressures

For the investigation of fluid flow in the supercritical state, computational fluid dynamics (CFD) have become increasingly important to gain information that cannot be obtained experimentally. Especially at near-critical pressures, the application of CFD methods is still a challenging task due to the strongly varying thermo-physical properties that complicate the solution process of the Favre-averaged conservation equations. The focus of the present work is on a numerical model (ANSYS FLUENT®) simulating flow and temperature fields of supercritical water jets discharged in a subcritical water bath at near-critical pressures. However, the used turbulence model tended to overestimate the values of the turbulent thermal conductivity near the pseudo-critical point of water. Various approaches based on a variable turbulent Prandtl number are presented to deal with these difficulties. Additional experiments were performed in a high-pressure vessel to record axial temperature profiles of the supercritical water jet and validate the numerical model.