Flow and heat transfer characteristics of 3D printed sheet and solid triply periodic minimal surfaces porous structures.

Triply periodic minimal surfaces (TPMS) are recently widely employed in thermal engineering applications due to their smooth surfaces, high surface area to volume ratio and mathematically controlled geometry features. Although the sheet-type TPMS shows good heat transfer capacity between the fluid and the skeleton surface, the pressure drop of this structure is large resulting from its partially disconnected surface. In this paper, four TPMS structures, sheet Gyroid, solid Gyroid, solid Primitive and solid Diamond were designed and manufactured by 3D printing technology. The heat transfer performance of different TPMS structures and the fin structure was researched by means of computational fluid dynamics (CFD) simulations and experimental methods. The results showed that the heat dissipation capability of the fin structure was better than that of the TPMS structures under ultra-low speed airflow. Otherwise, the heat transfer performance of the solid TPMS is better than both of the sheet TPMS and the fins structures. Although the sheet TPMS has higher surface area compared to the solid TPMS, the flow speed was decreased along the internal channels leading to greater thermal resistance and lower thermal transferring efficiency. When the gas velocity was less than 4 m/s, the solid Gyroid expressed the best performance among the three solid TPMS structures caused by its higher surface area connected to the heat source. Under higher gas velocity, the solid Diamond was proved to have better performance led by higher flow speed within channels. The heat transfer coefficient of solid Diamond was 110% and 59% larger than that of the solid Primitive and the solid Gyroid, respectively. The Nusselt number of solid Diamond was 10% and 12% greater than that of the solid Primitive and the solid Gyroid, respectively. The research proves that the solid TPMS can be used to replace the fin structure in heat exchangers and provides a basis for design and optimization of TPMS-based heat exchangers in the future.