Optimal Sizing and Material Choice for Additively Manufactured Compact Plate Heat Exchangers

Abstract

Advances in additive manufacturing (AM) enable new opportunities to design compact heat exchangers (cHEXs) by leveraging flexible geometries to improve energy and material efficiency. However, it is well known that reducing size in counterflow cHEXs can degrade effectiveness due to axial heat conduction through the solid material, which depends strongly on material thermal conductivity and wall thickness. Understanding the interaction between fundamental heat transfer mechanisms and manufacturing constraints is essential for designing next generation compact thermal systems that fully exploit AM's shaping flexibility. This study investigates how material selection and AM thin wall limitations influence the maximum achievable power density in compact plate heat exchangers. An optimization framework evaluates six materials including plastic, austenitic steel, Al2O3, AlN, aluminum, and copper under fixed pressure drop and effectiveness, while accounting for AM specific thickness constraints and a minimum plate spacing to address fouling risks. Results show that copper consistently yields the lowest power density despite having the highest thermal conductivity, whereas plastic achieves the highest power density across most optimization scenarios. Without manufacturing or fouling constraints, plastic outperforms the baseline steel design by nearly three orders of magnitude. With uniform plate thickness or fouling constraints, the performance gap narrows, making plastic and austenitic steel comparable. When material specific thickness limits are applied, plastic again leads in compactness due to its superior thin wall manufacturability. These findings highlight that AM constraints strongly affect cHEX compactness and that lower conductivity materials can outperform metals such as copper in power dense heat exchanger designs.