Numerical Analysis on Fully Developed Laminar Forced Convective Heat Transfer in Circular Tube with Internal Longitudinal Fins

Abstract

Fully developed laminar forced convective heat transfer in a circular tube with internal longitudinal fins is analyzed by using the finite difference method under two kinds of thermal boundary conditions at the outer tube wall (i. e., constant wall temperatures and uniform heat fluxes). Extended Nusselt numbers based on the outer wall temperature are compared for a wide range of geometrical parameters and the following results are obtained : (1) For small values of the ratio of tube-material-to-fluid thermal conductivities heat transfer augmentation by fins is not effective. (2) When the thermal conductivity ratio lies in the order of 100, the effect of the wall thickness on the heat transfer coefficient can be neglected. Furthermore in the case that the ratio is greater than 500, the thermal resistance of the fin can be ignored in respect to the heat transfer.