Flow and heat transfer in a plain fin-and-hexagonal tube heat exchanger with different side ratios

Improving the thermo-hydraulic performance of heat exchangers (HEs) can considerably manage the energy requirements in various engineering processes. The fin-and-tube heat exchangers (FTHEs) are extensively utilized in recent decades, and they provide substantial benefits over the typical HEs such as high heat transfer surface. The shape and geometry of the tubes remarkably affect the thermal efficiency and pressure drop of these devices. There are many experimental and numerical investigations relating to improving the thermo-hydraulic performance of FTHEs with circular and elliptical tubes in the literature. In the current research, five various hexagonal tubes with different side ratios were utilized to enhance the performance of an FTHE. The impact of various hexagon side ratios on heat transfer capacity and fluid flow characteristic of the FTHE at different Reynolds numbers has studied numerically. According to the obtained results, the plain -fin-and hexagonal tube HE with the side ratio of 0.25 had the best performance. Although the lowest values of the Colburn factor and the weakest heat transfer belong to the FTHE with the side ratio of 0.25, it is preferred to circular tube HEs due to the lower pressure drop they cause.