Convective Heat Transfer in Gas-Cooled Nuclear Reactors—A Review

Gas-cooled reactors are highly sophisticated energy systems in which numerous physical phenomena take place at the same time. Among these, the effective removal of heat from the reactor core is of great importance. In gas-cooled reactors, convective heat transfer and the conditions under which it occurs are critical to both the performance and safety of these reactors. Convective heat transfer in gas-cooled reactors is particularly complex due to the thermo-physical properties of gaseous coolants, high operating temperatures, and diverse flow regimes. It is commonly characterized using empirical and semi-empirical correlations. Each correlation is valid only within specific ranges of operating and geometric conditions, making the appropriate selection of correlations essential for accurate reactor design and reliable safety assessment. The aim of this review is to provide a comprehensive evaluation of the models and correlations applicable to the description and modeling of convective heat transfer in selected types of gas-cooled reactors. For each reactor type, the relevant correlations are categorized and summarized in tables, along with their ranges of applicability and inherent limitations. In total 154 correlations were reviewed. The findings highlight that convective heat transfer in different types of gas-cooled reactors is described differently. This article offer a consolidated reference of correlations useful for engineers and researchers working in the field of heat transfer and nuclear reactor engineering. In addition, remaining challenges are discussed and future research directions are proposed to support improved heat transfer modeling for current and next-generation gas-cooled reactor technologies.