Influence of finite-amplitude wave-induced sloshing on heat transfer characteristics of supercritical LNG in PCHEs

The printed circuit heat exchanger (PCHE) is widely regarded as the preferred primary heat exchanger for offshore liquefied natural gas (LNG) regasification, and is inevitably subjected to wave-induced sloshing. Although extensive research has been conducted on fluid heat transfer in PCHEs under floating conditions, wave-induced dynamic body forces are commonly idealized as sinusoidal oscillations, neglecting their finite-amplitude nature in real ocean waves. It remains uninvestigated whether simplifying the marine sloshing environment to an idealized sinusoidal motion adequately captures the flow and heat transfer features induced by real wave loads. To address this gap, this study develops a transient heat transfer model for PCHEs featuring straight channels with a semicircular cross-section, explicitly incorporating the LNG vaporization process occurring in floating storage and regasification units (FSRUs). The thermal performance predictions are systematically compared across models employing sinusoidal wave excitation versus finite-amplitude wave representations, including Stokes waves, cnoidal waves, and solitary waves, which provide a more physically informed approximation than linear waves. This study aims to identify the key wave parameters that govern thermal-hydraulic performance and to critically assess the validity and limitations of the sinusoidal wave assumption in PCHE thermal analysis. The results indicate that wave features, particularly their nonlinearity and finite-amplitude characteristics, exert a significant influence on the thermal performance of supercritical LNG. Especially for cnoidal and solitary waves under rough-sea conditions, the maximum temperature differences relative to the sinusoidal wave case are 0.311 K and 0.232 K, respectively. Within the large-specific-heat region, the discrepancy narrows due to the dominant influence of enhanced buoyancy forces. The local friction factor ( f ) profile of the Stokes wave conditions closely aligns with that predicted by the sinusoidal wave model, exhibiting a maximum relative deviation of only 0.29%; in contrast, the cnoidal wave induces more pronounced axial fluctuations in the local f , peaking at 1.20%.