Annular ducts : nusselt number correlations for laminar flows of liquids with temperature dependent properties

Abstract

Papers presented to the 11th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, South Africa, 20-23 July 2015.In this work, new correlations are proposed for the mean Nusselt number in the entrance region of concentric annular ducts with uniform heat flux boundary conditions specified at the inner wall. These correlations are obtained on the basis of the numerical results of a previous parametric investigation on the effects of temperature dependent viscosity and thermal conductivity in simultaneously developing laminar flows of liq- uids in straight ducts of constant cross-sections. A superposi- tion method is applied for the estimation of the Nusselt number by considering separately the effects of temperature dependent viscosity and thermal conductivity.