Design and performance Assessment of Straight, Zigzag, and airfoil fin configurations in 100 kW supercritical CO2 PCHE for enhanced Pre-Cooler application

The design of the fins of the Printed Circuit Heat Exchanger (PCHE) pre-cooler significantly impacts the efficacy and cost of supercritical carbon dioxide (sCO₂) Recompression cycles. This study uses a novel iterative discrete nodal approach to assess the performance of straight, zigzag, and airfoil-finned PCHEs under varying intake conditions in an innovative effort to address critical voids in the current understanding of fin configurations’ impact on PCHE performance. The analysis employs a cutting-edge Python-based design code and CoolProp for working fluid properties (RGP). The fins’ geometry significantly affects the pressure drop and heat transmission rate on the sCO₂ side of the PCHE. Straight fins exhibit the lowest thermal performance but the smallest pressure drop. In contrast, Zigzag and Airfoil fins (AFF) achieve higher heat transfer due to enhanced turbulence from their confined flow paths. The straight, zigzag, and airfoil fins maintain a ratio of sCO₂ pressure drop of approximately 1:7:2 across all inlet conditions. Nonetheless, Zigzag channels show an improvement in heat transfer rate over Airfoils of roughly 3 %, and this gain decreases further at higher sCO₂ inlet pressures. Thus, the Airfoil fin structure offers the best balance, providing heat transfer performance equivalent to Zigzag fins with a marginal pressure increase over straight fins. For the off-design performance analysis, sCO₂ inlet pressure (7.5 MPa-11 MPa), inlet temperature (65 °C-110 °C), and flow rates (0.4 g/s-1.4 g/s) are the key parameters, suggesting that heat transfer improves with increasing intake pressure, temperature, and flow rate for any fin arrangement. As the inlet pressure and temperature rise, the pressure drop of both fluids reduces. Inlet pressure exceeding 9 MPa reduces pressure drop gains at a rate of 10 % per MPa, signifying diminishing benefits for both fluids. Higher flow rates lower water-side pressure drop but increase sCO-side pressure drop by roughly sevenfold, making operation beyond 0.6 g/s unfeasible and negating heat transfer gains.