Direct numerical simulation of turbulent heat transfer in pipe flows with various prandtl numbers

The direct numerical simulation (DNS) of heat transfer in a fully developed turbulent pipe flow with for various Prandtle numbers are performed to obtain statistical quantities such as turbulent heat flux, and temperature variance. Main emphasis is placed on Prandtl number effects on turbulent heat transfer in pipe flow. Probability density functions and joint probability density functions of velocity and temperature fluctuations are used to describe the characteristics of the turbulent flow and heat transfer. The scaling temperature and velocity profiles are investigated in order to derive correct logarithmic law for various Pr. Evidence shows that temperature fluctuations and turbulent heat fluxes are increasing when increasing Prandtl number increasing. With decreasing Pr, the conductive sublayer at both walls spreads from the walls to the core region, while the root mean square of temperature fluctuations and the turbulent heat fluxes are reduced near both walls.