Numerical Study of Heat Transfer Mechanism in Turbulent Supercritical CO2 Channel Flow

Abstract

Direct numerical simulation (DNS) of superctitical CO2 turbulent channel flow has been performed to investigate the hear reansfer mechanism of supercritical fluid. In the present DNS, full compressible navier stokes equations and Peng-Robison stat equations are solved. due to the effects of the mean density variation in the wall normal direction, mean velocity in the cooling region bcomes high compared with that in the heating region. The mea width between the high and low speed streaks near the wall decreases in the cooling region, which means that turbulence in the cooling region is enhanced and lots of fine scale eddies are created due to the local high reynolds number effects. From the turbulent kinetic energy budget, it is found that compressibility effects related with pressure fluctuation and dilation of velocity fluctuation can be ignored even for supercritical condition. however, the effect of density fluctuation on turbulent kinetic energy cannot be ignored. In the cooling region, low kinematic viscosity and high thermal conductivity in the low speed streaks modify the fine scale structure and turbulent transport of temperature which results in high Nusselt number in the cooling condition of the supercritical CO2