Laser 3D-printed Periodic Porous Structures for Heat Exchangers: A Novel Characterization Approach Under Fully Developed Conditions

Triply Periodic Minimal Surfaces (TPMS) have garnered significant attention in recent years because of their potential for enhancing heat transfer performance. Recent advances in additive manufacturing have made it possible to fabricate these complex geometries; however, accurately characterizing their thermal-hydraulic performance remains challenging. To address this, this paper proposes a novel approach leveraging periodic boundary conditions to simulate fully developed flow and heat transfer within TPMS, eliminating inlet/outlet effects to focus on the structure's core region. The methodology was validated against experimental literature, showing excellent agreement in Nusselt number predictions. A case study on gyroid-based heat exchangers investigated the impact of edge dimension and wall thickness on performance. Key findings reveal that the Performance Evaluation Criterion (PEC) increases with porosity, with all designs exceeding the efficiency of traditional smooth ducts (PEC > 1). Specifically, gyroids with 45-50% porosity were identified as optimal, achieving a maximum PEC of 6.5 while strictly satisfying Laser Powder Bed Fusion (LPBF) printability constraints (minimum channel diameter > 1.2 mm). Furthermore, a simplified correlation between the Nusselt and Forchheimer numbers is proposed to streamline future design optimizations. By providing a rigorous framework for characterization, this work enables the development of highly efficient and innovative thermal management solutions.