Abstract
The fluid flow and heat transfer characteristics of the supercritical pressure fluids are of great importance in supercritical steam generators. This study utilizes the Computational Fluid Dynamics method with RNG k-ε turbulent model couple with enhanced wall function to analyze supercritical water heat and transfer characteristics in tubes with four types of variable inclination angles. the was used for numerical calculation. The numerical model got verified by experimental datas of supercritical water heated in a upward vertical tube. The flow and heat transfer in straight tubes with variable inclination angles were further analyzed and compared.
The distribution of supercritical water secondary flow distribution and turbulent kinetic energy in straight tubes with variable inclination angles were analyzed. The secondary flow vortex curved symmetrically at left and right with buoyancy force, and the secondary flow plane is perpendicular to the mainstream direction. Based on Hall’s and Jackson’s criterion, the influence of buoyancy force on heat transfer in tubes was quantitatively explained. Based on McEligot’s criterion, the influence of thermal acceleration got evaluated. It was found that the maximum value of heat transfer coefficients appeared before the pseudo critical point. In straight tubes with variable inclination angles, secondary flow vortex enhances heat transfer capability near the side, and the heat transfer coefficient near this angle is significantly higher than that near the bottom.
