Overview
This study investigates the optimization of variable triply periodic minimal surface (TPMS) lattice structures within additively manufactured heat exchangers. The research introduces a macroscopic modeling approach to analyze and optimize the flow patterns in a two-fluid heat exchanger equipped with a TPMS Primitive lattice, specifically focusing on regulating the relative dominance of hot and cold flows. The optimized solution, derived from this macroscopic model, was experimentally validated and demonstrated practical performance advantages.
Research Context
Heat exchangers incorporating TPMS lattice structures are a topic of research interest due to their potential to achieve uniform flow distribution, disrupt boundary layers, and enhance convective heat-transfer performance. However, traditional uniform lattice configurations may not represent the optimal macroscopic flow pattern for maximal heat-exchange efficiency. This suggests a need for methodologies that can optimize lattice distributions heterogeneously to improve overall heat exchanger performance.
Approach
The research began by developing a macroscopic modeling approach for a two-fluid heat exchanger utilizing a TPMS Primitive lattice. The macroscopic flow analysis was based on the Darcy–Forchheimer theory. To model heat transfer, an assumption was made that heat exchange occurs exclusively at the interface between the fluid and the TPMS walls. A macroscopic heat-transfer model was then formulated using a volumetric heat-transfer coefficient. This coefficient is characterized as an artificial property representing the unit-volume heat-transfer capability.
To control the relative influence of the hot and cold fluid flows, effectively modifying channel widths within the heat exchanger, the isosurface threshold of the Primitive lattice was selected as the design variable. An optimization scheme for the lattice distribution was constructed using the macroscopic model developed. This optimization was subsequently applied to a planar heat exchanger configuration, where both hot and cold fluids followed U-shaped flow trajectories. The optimal solution was verified through detailed geometric analysis. Experimental validation was conducted using metal LPBF (Laser Powder Bed Fusion) to produce the heat exchanger, and its performance was evaluated.
Findings
The macroscopic model successfully generated an optimal solution for the variable-TPMS lattice distribution. This optimal solution was subsequently verified through detailed geometric analysis, confirming its theoretical validity. Experimental results, obtained from heat exchangers manufactured using metal LPBF, indicated that the optimal solution derived from the macroscopic model demonstrated a clear performance improvement compared to a uniform lattice configuration. Specifically, an average enhancement of 28.7% in heat-transfer performance was observed in the experimental results when comparing the optimized design to a uniform lattice.
Why This Matters
The findings indicate that optimizing TPMS lattice distributions for specific flow priorities can lead to substantial improvements in heat exchanger performance. The developed macroscopic modeling and optimization approach provides a method for designing more efficient additively manufactured heat exchangers by tailoring their internal structures to fluid dynamics and heat transfer goals.