Thermal and Hydraulic Characterization of Hook-Shaped Fins and Dimples

Abstract

In forced convection, extended surface arrays enhance heat transfer by increasing surface area, promoting fluid mixing, and generating turbulence. Their thermal-hydraulic performance can be modified by introducing tip clearance or adjusting the attack angle. This study quantifies the heat transfer coefficient and pressure drop of GRIPMetal arrays – hook-shaped fins with dimples – under varying tip clearances and attack angles. Experiments with water-cooled GRIPMetal surfaces explored Reynolds numbers (Re) from 600 to 12,000, while simulations examined attack angles (α) from 0° to 90°. Results showed that GRIPMetal significantly outperforms smooth surfaces, with Nusselt number (Nu) enhancements of 2.4 to 5.7 times higher, despite increased pressure drop. Accounting for the pressure drop penalty, the overall performance factor remained above 1.4. Numerical findings revealed that α = 22.5° improved Nu by 44% at Re = 5000, and some configurations reduced pressure drop. These results highlight GRIPMetal’s potential as a cost-effective heat transfer enhancement method.