ANALYSIS OF HEAT TRANSFER IN INTERNALLY FINNED TUBES UNDER LAMINAR FLOW CONDITIONS
An analytical study of the laminar, fully developed, forced convection heat transfer in internally finned tubes was conducted. The adopted fin profile is defined by two radial flanks encompassing a variable angle and having a variable height. The tip of the fin is a circular arc concentric with the tube. Peripherally uniform temperature was assumed around the inner surface of the tube. The solution is based on a division of the heat flow domain into two regions, one is the central circular region of the fluid extending to the tips of the fins and the second region constitutes the remainder of the flow area. Solutions for the dimensionless temperature distribution within each region were developed analytically with arbitrary constants, the values of which were then calculated by matching the temperature and heat flux at the interface between the two regions. The dimensionless temperature and Nusselt number based on the inside tube diameter were determined for the full range of fin height and a varying fin width as well as number of fins, and the effects of all these parameters are presented and discussed. For all combinations of fin height and thickness it was found that Nusselt number increases with the increase of the number of fins up to a critical fin number beyond which a reversal of trend occurs.