Advancing recuperated supercritical carbon dioxide (sCO₂) Brayton cycle performance: Microchannel heat exchangers vs. traditional compact designs

The recuperated supercritical carbon dioxide (sCO₂) Brayton cycle offers high thermal efficiency for nuclear, solar, and waste heat recovery applications, but optimizing recuperator heat exchangers is challenging due to pressure losses and limited heat transfer performance. Using ANSYS Fluent, this study evaluates the thermal-hydraulic performance of microchannel and compact heat exchangers with varying geometries (rectangular, triangular, elliptical) and hydraulic diameters (400–1500 μm). Results show microchannels reduce volume by 50–70 %, with elliptical designs achieving the highest compactness and a 70 % increase in volumetric power density. Microchannels with 400 μm diameter demonstrated up to 15 % higher effectiveness, 40 % greater NTU, and required 50 % less flow length for 90 % effectiveness. Triangular and elliptical microchannels improved thermal performance by 30 % under higher pumping power but incurred 20 % more frictional losses. The obtained results were further compared with an emerging heat exchanger technology. Empirical correlations developed accurately predict performance, advocating microchannel heat exchangers as superior for enhancing sCO₂ Brayton cycle efficiency.