Thermal - hydraulic performance and heat transfer modelling of partially filled stochastic metal foam heat sinks

This study presents an experimental investigation of the thermal and hydrodynamic performance of a rectangular channel heat sink partially filled with unstructured open-cell copper foam. The foam has a porosity of 0.9625, 30 pores per inch ( P P I ) , and a height of 20 m m . Three configurations are examined based on the foam-to-channel height ratio (Blockage ratio = H f / H = 1.0 , 0.75 , and 0.5 ), representing fully and partially filled cases. The Reynolds number, calculated using channel hydraulic diameter, varies between 5000 and 25000. Local temperature distributions along the heater wall are captured using infrared (IR) thermography and a thin stainless-steel foil technique. Results show that the pressure drop decreases by factors of 5 and 19 for H f = 0.75 H and H f = 0.5 H configurations, respectively, relative to the fully filled configuration, due to lower flow resistance in the gap regions. The fully filled foam configuration ( H f = H ) yields the highest heat transfer performance due to complete fluid-foam interaction, with a decreasing temperature difference ( T w ( p i x e l ) − T f ( P i x e l ) ) along the flow direction. In contrast, the partially filled cases exhibit increasing temperature differences downstream due to reduced fluid penetration into the foam. The thermal–hydraulic performance assessed using the Colburn factor j and friction factor f indicates that the H f = 0.75 H configuration provides an optimal tradeoff between heat transfer and pressure loss. A two-model framework is developed to predict mass flow separation and heat transfer in partially foam-filled channels, wherein Model 1 (experiment-based) establishes the benchmark and Model 2 (analytical) provides predictive capability. This integrated approach uniquely addresses flow partitioning in porous–bypass systems, a phenomenon not reported previously to the best of our knowledge. Generalised correlations are proposed for predicting heat transfer coefficients in partially filled porous channels. Overall, the study provides a design framework for optimising thermal performance while minimising pressure drop in systems employing unstructured metal foams.