Analysis and calculation of coupled convection and conduction for laminar flow in a tube

It is shown that axial heat conduction in the wall of a tube can have a significant effect upon heat transfer between the wall and a fluid flowing under laminar conditions in the tube. The case of present interest is fully-developed flow in the thermal entry region; an area in which coupled convection/conduction effects render experimental measurement difficult. The axial development of Nusselt number along the tube demonstrates marked departure from the behaviour found in the absence of wall conduction. Examination of the governing equations reveals that Nusselt number is a function of dimensionless position and a third non-dimensional group, the ''conduction influence parameter''. An iterative numerical scheme is used to calculate Nusselt number for several values of this parameter. The results are related to a particular physical system by reference to flow of carbon dioxide in a mild steel tube. (author)