Experimental Measurement and Numerical Modelling of Solid Network-Based Schoen’s I-Graph—Wrapped Package (I-WP) toward Cooling Heat Sink

Triply Periodic Minimal Surfaces (TPMS) are periodic implicit surfaces with zero-mean curvature. Zero-mean surfaces are those that locally have minimum surface area for a given boundary. This study investigates the thermal performance of a TPMS geometry, Schoen’s I-graph Wrapped Package (I-WP), for application as a compact heat sink. While most prior work focuses on gyroid-based TPMS structures, this research explores the less-studied I-WP architecture fabricated from copper with a fixed porosity of 0.7. The influence of unit cell size on convective heat transfer and flow resistance is examined both experimentally and numerically. Experimental testing was conducted for unit cell sizes of 4 mm, 6 mm and 8 mm, while numerical simulations using COMSOL Multiphysics extended the analysis to sizes of up to 14 mm. Strong agreement between the measured and simulated results (within a 3% temperature deviation and 7% for the local Nusselt number) validated the numerical model. Empirical correlations for the average Nusselt number were developed based on both experimental and numerical data. The novelty of this paper lies in the performance of the experiment for different flow rates and unit cell sizes. The study identified 12 mm as the optimal unit cell size, yielding the highest Performance Evaluation Criterion (PEC) and demonstrating an effective balance between thermal enhancement and hydraulic performance. Furthermore, uniform temperature distributions observed across the flow direction underscore the advantages of TPMS structures over conventional metal foams. These findings establish the I-WP geometry as a promising candidate for next-generation, geometrically tunable heat exchangers that can be enabled by additive manufacturing.