Experimental Investigation of Thermal-Hydraulic Performance of Externally Finned Tubes

Abstract

Currently there are various concepts of heat transfer intensification, on the basis of which methods have been developed to increase the heat transfer coefficient in the channels of heat exchange surfaces, which do not lead to significant additional energy costs for flow movement. The article presents the results of an experimental study on the influence of various types of fins on heat transfer processes and hydraulic resistance. The results obtained show that fins in the form of crosses and triangles are the most efficient in terms of heat transfer. However, they create the greatest hydraulic resistance. The largest value of the Nusselt number is relevant for fins type 5 and 6 due to a more active effect on the core of the flow owing to its shape. Fins 7 and 4 have the minimal influence, since they have the ‘smoothest’ shape. Studies have shown that with Reynolds numbers in the range of 13,000–32,000, fins of type 4 and 7 show the greatest resistance. It is shown that it is possible to switch from pipes without fins to pipes with fins by including the coefficient B in the Nusselt equation having a range of 0.03–0.061. It is shown that under certain conditions, heat transfer when using fins can decrease with increasing Reynolds number.