Flow and heat transfer behavior of supercritical CO2 in different PCHE channels under rolling motions

Abstract

Supercritical carbon dioxide (S-CO₂) Brayton cycles hold significant promise for offshore power systems, where compactness and efficiency are critical. However, ocean-induced rolling motion can impact the thermal performance of key components such as the precooler, which is usually in the form of a printed circuit heat exchanger (PCHE). This study focuses on the flow and heat transfer characteristics of S-CO₂ in straight, sinusoidal wavy, and zigzag PCHE channels under both stationary and rolling conditions. Comparative analysis is made among channel geometries subjected to dynamic marine environments, which has been scarcely explored in prior work. Results show that rolling motion elicits periodic oscillations in heat transfer coefficients and pressure drops, with amplitudes scaling with rolling angle. At a rolling period of 2 s and a maximum angle of 30°, the relative changes in heat transfer coefficient reach 0.25 %, −0.02 %, and 5.57 % for the straight, sinusoidal wavy, and zigzag channels, respectively, while the corresponding relative changes in pressure drop are 446.59 %, 163.63 % and 78.45 %. Forces along the mainstream direction are the primary driver of these fluctuations, while the inertial forces perpendicular to the mainstream have a comparatively minor impact. Notably, the sinusoidal wavy channel demonstrates an anti-rolling capability due to centrifugal forces, whereas the zigzag channel benefits from intensified secondary flow, leading to enhanced heat transfer. These findings can offer guidelines for the design of robust PCHEs in offshore S-CO₂ systems operating under rolling conditions.