heat exchanger

film cooling

nusselt number

flow heat transfer

capillary tube

heat exchangers

heat transfer enhancement

twisted tape

tube heat

International Journal of Thermal Sciences

This study proposes a novel type of tube with helical dimples. Turbulent heat transfer and flow resistance in a heat exchanger tube with helical dimples were numerically investigated. Furthermore, the effects of the geometric parameters, including spiral pitch, transverse length, number of starts, depth, and radius on the performance were investigated. The results demonstrated that the longitudinal swirling flow and vortex generated behind the helical dimples result in adequate fluid mixing between the mainstream and near-wall regions. Therefore, the thermal performance of the tube with helical dimples was enhanced by 120–270% in comparison with the plain tube. Both Nu / Nu 0 and f/f 0 increased with increasing dimple starts, depth, and radius and decreasing spiral pitch and transverse length. Additionally, a maximum PEC = 1.93 was obtained by employing the geometric model with P = 30 mm, L = 6.9 mm, N = 4, D = 2 mm, and R = 2 mm in all cases.

Numerical investigation of thermal-hydraulic performance of a heat exchanger tube with helical dimples