A New Correlation for the Turbulent Prandtl Number in Upward Rounded Tubes in Supercritical Fluid Flows

Numerical results show that at supercritical pressures, once the buoyancy force increases, the effect of the turbulent Prandtl number, Pr-t, on convective heat transfer becomes considerable. This phenomenon has not been adequately addressed in the literature. In this study, the effect of the turbulent Prandtl number on the rate of heat transfer in both enhanced and deteriorated regimes of heat transfer to supercritical fluid flows has been extensively investigated. Having realized that variations of the turbulent Prandtl number can affect the model predictions so greatly, a new correlation to express the changes of Pr-t with respect to flow conditions in a supercritical environment is developed. Effects of various important parameters such as heat flux, mass flux, and fluid pressure are included in the proposed correlation. This correlation has been modified to be applicable for different supercritical fluids. The comparison with various experimental data shows that by implementing the new correlation of Pr-t in the numerical code, it is possible to significantly improve the simulation results. Such a correlation seems to be the first one introduced in the literature for a supercritical fluid flow.