Numerical study of heat transfer deterioration of turbulent supercritical kerosene flow in heated circular tube

摘要

Turbulent flow and convective heat transfer of supercritical kerosene flow in an axisymmetrically heated circular tube with a diameter of 2 mm and at a mass flow rate range of 0.0015-0.015 kg/s and a wall heat flux range of 0.15-2.0 MW/m~2 are numerically studied using Reynolds averaged Navier-Stokes method with a two-layer turbulence model. The thermophysical and transport properties of kerosene are determined by a 10-species surrogate with the Extended Corresponding State method. Mesh dependency is first investigated and numerical results of fuel and wall temperatures are compared with experimental data for validations. The results show that flow properties such as velocity and Reynolds number increase significantly along the axial direction as the fuel temperature rises and kerosene undergoes the state transition from liquid to supercritical state. Deterioration of convective heat transfer is found to occur when the wall heat flux exceeds a critical value and at the same time, the wall temperature approaches the pseudo-critical temperature of kerosene. The present results show that deterioration of heat transfer are attributed to the development of turbulent properties in the near-wall region based on the results of turbulent kinetic energy and turbulence production term. The relation between the critical heat flux (q_(wc)) for occurrence of heat transfer deterioration and the mass flux (G) is studied and a fitting formula of q_(wc) and G is obtained.