Design and optimization of a novel half-airfoil-fin curved rectangular channel structure for conformal heat exchangers in underwater power system

The ocean, as the largest resource reservoir, is increasingly explored via submarines, submersibles, and underwater space stations. Carbon dioxide (CO₂) power cycles suit underwater platforms by providing compact, safe, high-power-density output within limited cylindrical volume. Printed circuit heat exchangers (PCHE) are high-effectiveness heat exchangers of CO₂ power cycles, but conventional straight channel designs cannot conform to curved cylindrical hulls, reducing space utilization and power density. Conformal PCHE (C-PCHE) can address this constraint, but their curved channels introduce centrifugal force, flow non-uniformity, and boundary-layer variations and other effects, making straight channel design rules and optimizations non-transferable. Currently, design and optimization of conformal channels remain underexplored. This study first clarifies the dominant flow mechanisms of conformal channels through a conformal redesign of the typical PCHE channels, and then proposes a manufacturable half-airfoil-fin curved rectangular channel to suppress curvature-induced maldistribution and strengthening near-wall mixing. The fin arrangement and geometric parameters are systematically analyzed and optimized. A pitch-dependent layout and sizing regime is established to provide transferable design rules for C-PCHE channel selection under cylindrical constraints. Results show that the optimized half-airfoil-fin curved rectangular channel outperforms the curved rectangular channel in heat transfer, achieves higher heat transfer with lower pressure drop than the curved zigzag channel, and delivers superior comprehensive performance to the curved airfoil-fin channel, with comprehensive performance improvements of 29.0–112.1%, 29.7–66.0%, and 9.5–43.1%, respectively. The proposed channel enables compact, high effectiveness, fabrication-feasible C-PCHE design and mitigates centrifugal-force-induced flow maldistribution in cylindrical underwater energy systems. • Presents the first conformal design of typical PCHE channels for cylindrical hulls. • Proposes a novel manufacturable half-airfoil-fin curved rectangular channel. • Develops airfoil-inspired flow control to suppress centrifugal maldistribution. • Achieves higher heat transfer at lower pressure drop than curved zigzag channels. • Provides transferable pitch-based layout and sizing rules for conformal PCHE.