A turbulence model for momentum and heat transfer in internal flow of viscous non-Newtonian fluids

摘要

This paper presents a turbulence model for the internal flow of viscous non-Newtonian liquids. Since the apparent Prandtl numbers of the power law fluids are high, it is found that the laminar sublayer thickness for momentum is different from that for heat transfer. Values and expressions are obtained for the normalised momentum and thermal thicknesses of the laminar sublayer. A theoretical equation is obtained for the friction coefficient as a function of the apparent Reynolds number. An expression for Nusselt number is also obtained as a function of the apparent Reynolds and Prandtl numbers by applying Prantdtl's analogy to viscous non-Newtonian fluids. The friction and heat transfer coefficients predicted by the present theoretical analysis are in good agreement with the experimental data for polymer solutions of concentrations from 0.25 to 2%, and for a wide range of system parameters (10000