Heat Transfer in Supercritical Fluids: A Review

Abstract

Supercritical fluids (SCF) find potential applications in the upcoming energy systems due to various advantages associated with them. One of such applications is nuclear reactor where supercritical water and carbon-dioxide, both are proposed as the coolants in advanced reactor designs. Higher efficiency, simplified systems, lower operational costs are some of the advantages which propels the research fraternity to employ these fluids in application. However, there are also some challenges associated with the use of these fluids. Heat transfer behavior of these fluids is one among them. As SCF undergo tremendous changes in thermophysical properties across pseudo-critical temperature, heat transfer may get affected. It may get enhanced, deteriorated or remain unaltered. Various studies, experimental and analytical, have been carried out in the past using SCF to evaluate their heat transfer behavior. Various heat transfer correlations have been proposed by researchers catering to different operating range of parameters. Also, studies have been dedicated by researchers to investigate fluid-to-fluid scaling of SCF based on which scaling laws were proposed by them. This way prototypic fluid behavior can be predicted if the model fluid conditions are known. This paper presents a latest review of the scaling laws and heat transfer correlations applicable to SC fluids. Illustrations have also been presented considering reference experimental data from literature to get a feel about how these scaling laws fare among themselves. Various heat transfer correlations have been compared and important observations have also been discussed in this article.