High-power electronics require heat sinks with excellent thermal–hydraulic performance. Although triply periodic minimal surface (TPMS) structures provide large surface areas and interconnected flow channels, conventional monolithic designs can suffer from nonuniform flow distribution and localized hot spots. The novelty of this work lies in introducing a functionally graded hybrid (FG-H) TPMS heat sink comprising Lidinoid, Split-P, and Diamond topologies sequentially stacked in the wall-normal direction away from the heat source at a constant porosity of 82.2%. Its performance was compared with that of monolithic Diamond (M−D), hierarchical nested Diamond (H-ND), and heterogeneous hybrid (H-H) TPMS designs. The different designs were analyzed using three-dimensional conjugate heat transfer simulations with a validated SST k–ω turbulence model over a Reynolds number (Re) range of 2,000–16,000. A total of 128 sampling planes were used to characterize momentum and thermal transport across each TPMS design, thereby enabling volumetric characterization of fluid transport within the porous space. The results indicate that FG-H achieved the highest Nusselt number (31.93) and the lowest pressure drop (236 Pa) at Re = 10,000, resulting in the best performance evaluation criterion (PEC) value of 1.75 compared with the other baseline designs. Furthermore, it provided 52.80% less hydraulic loss, 14.3% better cooling performance, 2.61-fold greater mean-field synergistic factor, 6.43% entropy reduction, and 71.4% reduction in temperature non-uniformity than the M−D baseline. Thus, among the investigated TPMS architectures, the overall performance ranking was FG-H, followed by H-H, M−D, and H-ND.
