Curved lancet pin-fin geometry effects on convective performance in microchannels

Efficient thermal management in compact cooling systems requires enhancement techniques that improve heat transfer while minimizing pressure penalties, particularly under transitional flow conditions. However, the effects of curvature-controlled pin-fin geometries in microchannel flows at moderate Reynolds numbers (Re = 1000–5000) remain insufficiently understood. In this study, a three-dimensional numerical investigation was conducted to evaluate the thermo-hydraulic performance of a microchannel heat sink equipped with curved lancet pin-fins. Four inclination angles (45°, 60°, 75°, and 90°) were systematically examined. A smooth channel was used as a baseline for comparison. The results showed that curvature-induced flow redirection significantly altered vortex structures, enhanced near-wall mixing, and suppressed large-scale wake regions. Among the tested configurations, the 45° case provided the best performance, increasing the area-averaged Nusselt number by up to 16.7% compared with the 90° case, while simultaneously reducing the friction factor by approximately 1.36%. As a result, the thermal performance factor improved by up to 16.9%, indicating a favorable balance between heat transfer enhancement and pressure loss. The novelty of this work lies in the systematic evaluation of curvature-angle effects on lancet-type pin-fins under transitional Reynolds-number conditions in confined microchannels. The findings provide new physical insight into curvature-controlled flow mechanisms and offer practical guidance for the design of compact cooling systems with improved thermo-hydraulic efficiency.