Comparative Assessment of Dimple Geometries for the Thermal–Hydraulic Performance of Finned‐Tube Heat Exchangers

ABSTRACT Finned‐tube heat exchangers are widely used in air‐conditioning, refrigeration, and industrial thermal systems, where enhancing heat transfer without an excessive pressure‐drop penalty remains a key challenge. Dimpled surfaces are a promising passive technique for this purpose. On the basis of the reviewed literature, the specific combination investigated in this study—truncated hemispherical dimples together with quarter‐spherical dimples arranged in streamwise, transverse, alternating, and both‐side transverse configurations—has not been systematically evaluated for finned‐tube heat exchangers. This study numerically evaluates these dimple shapes and arrangements by comparing six dimpled‐fin configurations with a plain‐fin design using the SST k–ω turbulence model. All dimpled configurations enhance heat transfer relative to the plain fin, with a corresponding increase in pressure drop. The transverse quarter‐spherical dimpled fin (TQDF) provides the highest heat‐transfer enhancement, with a 24.2% increase in heat transfer, a 30.27% rise in the j ‐factor, and a 42.95% increase in the friction factor at Re = 3200. The truncated hemispherical dimpled fin (THDF) and both‐side transverse quarter‐spherical dimpled fin (BTQDF) configurations also show considerable improvements, whereas the alternating streamwise quarter‐spherical dimpled fin (ASQDF) shows the least enhancement. All modified configurations yield performance evaluation criterion (PEC) values greater than unity, confirming a net thermohydraulic advantage. The streamwise quarter‐spherical dimpled fin (SQDF) achieves the highest PEC value of 1.1597 at the maximum Reynolds number, reflecting the best overall thermohydraulic trade‐off, while TQDF delivers the greatest heat‐transfer enhancement. These findings provide new design insights into the thermohydraulic effects of dimple geometry and arrangement for optimizing dimpled‐fin surfaces in finned‐tube heat exchangers.