Performance analysis of porous microchannel heat sinks with diverging geometry using phase-change fluids

In this study, the thermal and hydrodynamic performances of porous microchannel heat sinks with diverging geometries under phase-change fluid flow was comprehensively investigated through numerical simulations. Initially, the base model was validated against reliable experimental data, showing strong agreement with the benchmark results. Subsequently, 20 numerical models were simulated in ANSYS Fluent, encompassing four geometric configurations with divergence ratios of 2, 3, 4, and a constant cross section, as well as five porosity levels ranging from 0% to 80%. The goal was to assess the combined effects of geometric divergence, porous structure, and two-phase fluid behavior on the thermo-hydraulic performance of the system. The results revealed that increasing the divergence angle led to a pressure drop reduction of up to 25% and improved pressure distribution along the channel. Meanwhile, porosity enhanced flow uniformity and contributed to more consistent temperature profiles. In configurations with higher divergence and moderate porosity, the maximum wall temperature decreased by up to 18%, and the phase-change region shifted upstream, promoting earlier evaporation and improved cooling effectiveness. Optimized configurations with divergence ratios of 3–4 and porosity levels of 40%–60% demonstrated the best overall performance in terms of heat transfer enhancement, flow stability, and minimized pressure drop. These findings suggest that the strategic integration of diverging geometries and porous media design represents an effective approach for enhancing the efficiency of advanced cooling systems, particularly in microfluidic, electronic, and high-power energy applications. This study paves the way toward the development of a new generation of high-performance heat sinks.