Numerical Prediction of Turbulent Heat Transfer in High-Prandtl-Number Fluids

A two-equation heat-transfer model for high-Prandtl-number fluid flows has been developed from the scope of the original (t2)^^- εt model of Nagano and Kim (1988). The proposed model has been appraised in comparison mainly with the existing experiments on water (Pr=5.9), aqueous ethylene glycol (Pr=14.3) and oil (Pr=95). It is shown that the present model predicts quite well the experimental behavior of fundamental quantities in turbulent heat transfer, i.e., the Nusselt or Sherwood number, temperature profiles and intensity of temperature fluctuations. Especially, the prediction of the r.m.s. intensity of temperature fluctuations is in good agreement with the most recent and reliable experimental data of water. Furthermore, we have investigated the Prandtl-number dependency of the turbulence quantities in thermal fields such as Nusselt number, temperature profile, temperature variance and eddy diffusivity for heat. Since the two-equation heat-transfer model provides information on temperature fluctuations, which cannot be obtained by the conventional model based on the assumption of the turbulent Prandtl number, the present model provides a powerful tool for critical design of thermal equipments.