Review on Supercritical Fluids Heat Transfer Correlations, Part I: Variants of Fundamental Dimensionless Variables

When supercritical fluids absorb heat energy through channels, their thermophysical properties rapidly change, resulting in an enhanced, deteriorated, or normal heat transfer phenomenon. Understanding the phenomena of heat transfer is essential for applications involving supercritical fluids, particularly nuclear power generation. As a result, the Nusselt number correlation is developed and used to characterize the heat transfer performance under a variety of operating conditions, geometries, and flow directions. Unfortunately, for supercritical fluid heat transfer, there are now over 50 Nusselt number correlations, which create difficulties to comprehend all of the Nusselt number correlations due to their complex structures and distinctive formulations of the modifying factors. Therefore, this review article is devoted to providing a comprehensive yet succinct overview of the key components of the majority of supercritical Nusselt number correlations. The supercritical properties of water, carbon dioxide, and helium are briefly introduced, taking supercritical carbon dioxide as an example. The potential use of supercritical fluid in engineering applications, such as Generation IV nuclear reactors, waste heat recovery, and concentrated solar power, is presented. The origin and properties of the variants of the Reynolds number, the Prandtl number, and the reference temperature modified for the Nusselt number correlation are categorized and examined.