Flow and heat transfer mechanism of trans-critical natural gas in finned micro channels with variable cross section

Printed circuit heat exchangers (PCHEs) offer significant advantages in industrial applications such as liquefied natural gas (LNG) regasification due to their compact structure and high heat transfer efficiency. This study employed numerical simulations to systematically compare the flow and heat transfer characteristics of supercritical natural gas in straight, contracting, and expanding channels. Based on the principle of flow and temperature field synergy, the heat transfer characteristics of a segmented non-uniform finned channel were analyzed and compared with those of a traditional uniform finned channel. The simulations utilized the SST k-? turbulence model and the NIST real gas model to ensure accuracy. The results demonstrate that under identical operating conditions, the non-uniform channel more effectively mitigates irreversible losses and enhances field synergy, while simultaneously achieving structural miniaturization. Among the three variable cross-section channels, the expanding channel exhibited the best comprehensive thermal-hydraulic performance. Furthermore, the study evaluated the influence of operating parameters on the performance of the segmented non-uniform channel. It was found that the channel performs optimally near the design condition and maintains good adaptability to parameter variations. This research provides valuable insights and a practical numerical simulation methodology for the optimal design of PCHEs in LNG and related fields.