Gyroid-based PCM-water compact heat exchangers

Triply periodic minimal surface structures are investigated in heat exchanger configuration with phase change material and water as participating media. Gyroid-based monolith heat exchangers are additively manufactured via selective laser melting AlSi10Mg at three different porosities of 0.7, 0.75 and 0.8. Transient heat transfer experiments are conducted for a wide range of water flow rates to understand the effect of porosity and water flow conditions on the phase change material solidification. Besides experimental characterization, a computational fluid dynamics methodology is proposed to investigate the performance of the tested exchangers and is validated against experiments. This study shows that the lowest-porosity structure provides the best thermal performance in terms of total time required for phase change material solidification, with a reduction of nearly 40% compared to the highest porosity one. This performance is the result of higher convective heat transfer coefficient and effective thermal conductivity due to higher metal content. The highest-porosity specimen exhibits greater latent heat storage capability and lower water pressure drop, reducing the required pumping power to 40% of that associated with the lowest porosity structure. The total solidification time is found to be less sensitive to water flow rate for a given Gyroid porosity. In comparison with a conventional offset strip fins topology, the Gyroid structure exhibits higher performance evaluation criterion, thus offering higher global thermo-hydraulic efficiency.