Research on near-critical/trans-critical flow and heat transfer in engineering applications: A review

With the continuous advancement of energy technologies, increasingly efficient and sustainable methods for utilizing renewable resources are emerging. Fluids operating near or beyond the supercritical point exhibit exceptional thermophysical properties, making them a growing focus in advanced energy systems. Research on near-critical/trans-critical processes spans nuclear and thermal power, aerospace propulsion, CO2 transport, and compact circulation systems, with efforts aimed at enhancing system performance and safety. However, the pronounced nonlinearity of fluid properties near the critical point often results in abnormal flow and heat transfer behavior, presenting significant challenges in various applications. Unlike prior reviews, this study specifically investigates flow and heat transfer characteristics under near-critical/trans-critical conditions across diverse domains. Related systems are regrouped to highlight shared mechanisms, such as coupling supercritical water-cooled reactors (SCWRs) with other power systems and integrating regenerative cooling systems (RCSs). Trans-critical CO2 leakage in CO2 capture and storage (CCS) pipelines is identified as a critical transport issue, while microscale heat transfer (MHT) is discussed separately due to its distinct scale effects. The review encompasses a wide range of fluids, geometries, and length scales, facilitating cross-domain comparisons. Although semi-empirical correlations remain prevalent, their limitations under asymmetric heating, microscale constraints, and strong thermal–fluid coupling are emphasized. Key gaps include inadequate modeling of heat transfer deterioration in SCWRs, flow instabilities in RCSs, real-fluid effects in CCS, and a lack of microscale experimental data, underscoring the need for advanced modeling and broader cross-domain validation.