Modeling and validation of an additively-manufactured multi-pass microchannel heat exchanger for high power density applications

Supercritical CO 2 (sCO 2 ) has attracted considerable attention in multiple thermal applications, such as power generation systems, aerospace, and electronics, due to its high energy density. Its unique properties facilitate the development of high-performance, cost-effective, and compact metal heat exchangers. In addition, innovative designs enabled by additive manufacturing can further enhance thermal performance by increasing surface area density while regulating the pressure drop. In this study, we developed a small-scale, multi-pass microchannel heat exchanger (MPMHX) with a volume of 115,679 mm 3 and a surface area density of 989 m 2 /m 3 , which experimentally achieved a high power density of 45.4 MW/m 3 . The additive manufacturing process used to fabricate the HX introduced a channel relative roughness of 9.6 %, which increased the pressure drop by an average of 172 % compared to the smooth channel. Meanwhile, the roughness improved thermal performance by 31 % on average. In a comparison with other compact HX concepts in the literature, the MPMHX performance experimentally demonstrated the highest compactness (Q/V = 45.4 MW/m 3 , Q/V/dT = 0.34 MW/m 3 /°C) with a low pumping power of 11.75 W. This is the first study to provide experimental results for the additively manufactured multi-pass microchannel heat exchanger, demonstrating enhanced performance for high efficiency, extreme environment, and power generation applications. • Development of a compact Multi-Pass Microchannel Heat Exchanger (MPMHX) with asurface area density of 989 m 2 /m 3 . • MPMHX with 9.6 % roughness (AM) raised pressure drop by 172 % and boosted thermal performance by 31 % vs smooth channel. • MPMHX has a high, experimentally validated power density (Q/V = 45.4 MW/m 3 ) with a low pumping power of 11.75 W.