This investigation focuses on how longitudinally twisted fins influence the convective heat transfer and flow behavior within a 3-D aluminum heat sink. Using a finite element-based numerical model, the influence of fin twist angles, 10°, 15°, and 20°, was analyzed under laminar, incompressible, steady-state water flow conditions with Reynolds numbers ranging from 500-1500. The base of the heat sink is subjected to a constant heat flux of 20000 W/m², and the resulting flow and temperature fields were examined in detail. Velocity distributions revealed enhanced fluid mixing and vortex generation with increasing twist angle, while surface temperature contours and thermal gradients demonstrated improved heat removal performance. Quantitative metrics, including average heat transfer coefficients and Nusselt numbers, confirmed that the 20° twisted fins consistently outperformed the lower-angle configurations, especially at higher Reynolds numbers.