Numerical Prediction of Turbulent Pipe Flow Heat Transfe for Various Prandtl Number Fluids with the Improved k-ε Turbulence Model

Abstract

Numerical prediction has been made of the turbulent heat transfer in a fully developed turbulent pipe flow heated with a constant heat flux for a wide range of Prandtl and Reynolds numbers ; i.e., 10^-2<Pr<5×10⁴ and 10⁴<Re<10⁵. The improved k-ε turbulence model of Myong and Kasagi is employed with turbulent Prandtl number assumptions. It is demonstrated that the distribution of eddy diffusivity of momentum is of dominant importance to predict the turbulent heat transfer and also to evaluate the turbulent Prandtl number Pr_t. The effect of the Reynolds number on Pr_t is comparatively weak in the whole Pr range studied. In addition, Pr_t remains almost constant with the value near unity at Pr>0.5 and increases gradually with decreasing Pr at Pr«1. An empirical equation of Pr_t is proposed as a function of Pr over a wide practical Pr range.