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

摘要

Fully developed laminar forced convective heat transfer in a circular tube with internal longitudinal fins is analyzed using the finite difference method, with the proviso that the flow is also fully developed. We adopt two kinds of thermal boundary conditions at the outer wall of the tube: constant wall temperatures and uniform heat fluxes. Extended Nusselt numbers based on the outer wall temperature are compared for the wide range of the geometrical parameters and the follwing results are summarized: (1) The equivalent diameter of the conduit affects the velocity profile of the fluid and the resulting flow pattern controls the heat transfer mechanism. (2) When the thermal conductivity ratio of the fluid to the tube material is small, the heat transfer augmentation by the fins is not effective. (3) When the thermal conductivity ratio of the fluid to the tube material lied in the order of 100, the effect of wall thickness on the heat transfer coefficient can be neglect. Furthermore when this ratio is greater than 500, the thermal resistance of the fin can be ignored in respect to the heat transfer.