Recent Development of Heat Transfer and Fluid Flow of Supercritical CO₂ in Tubes: Mechanisms and Applications

With the advantages of low cost, excellent ability of heat and mass transfer and easy accessibility to the supercritical point, supercritical CO₂ has been applied in many engineering devices recently. Because of the sharply-varying thermophysical properties near the supercritical point, heat transfer and flow behavior of supercritical CO₂ in tubes become complex and have received a lot of research attention. The main purpose of this paper is to summarize the findings of the published works related to flow phenomena and heat transfer characteristics of supercritical CO₂. Firstly, influence parameters related to boundary conditions of supercritical CO₂ flowing in a smooth tube are introduced. Secondly, commonly-used turbulence and mathematic models dealing with internal flows of supercritical CO₂ are summarized. Then, research works on geometric effects of design parameters, shapes and configurations are introduced. The practical applications of supercritical CO₂ in recent years are presented. Finally, developments and future challenges of supercritical CO₂ in tubes are analyzed and summarized. This paper provides basic knowledge of heat transfer and fluid flow mechanisms and related practical applications of supercritical CO₂ in tubes.