Advanced Fundamental Studies on Supercritical Fluids

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Supercritical fluids are fluids at pressures above a critical pressure (critical pressure and temperature are characteristics of a critical point in which the distinction between the liquid and vapour phases disappears, i.e., both phases have the same temperature, pressure and volume). Critical parameters for water are pressure of 22.1 MPa and temperature of 374 C; for carbon dioxide - 7.4 and 31 C; and for R-134a - 4.1 and 101 C; respectively. Supercritical fluids exhibit a unique set of properties, which allow to store a lot of energy during heating and retrieve this energy during cooling or during expansion through a turbine, which make them ideal working fluids or coolants for use in a variety of industrial and laboratory applications. The largest industrial application of supercritical fluids is the extensive use of supercritical water in power industry in supercritical-pressure coal-fired power plants, which have quite high thermal efficiency (up to 55%) compared to other power plants. However, there are many other areas of application for these fluids such as coolants in Generation-IV nuclear-reactor concepts (supercritical water and helium); in power cycles of these reactors (supercritical water, helium and carbon dioxide); etc. Specifics of supercritical fluids' properties have significant impact on heat transfer and pressure drop at these conditions. Despite more than 60 years of active research into supercritical fluids, many of physical phenomena and behavioural characteristics are not fully understood (for example, improved and deteriorated heat-transfer regimes, pseudo-boiling, pseudo-film boiling, etc.). Solid knowledge and understanding of thermophysical properties and heat-transfer specifics at supercritical pressures are very important for a safe and efficient use of supercritical fluids in various industries. The applicant has made significant progress investigating specifics of supercritical fluids that have resulted in numerous publications and the first technical book on heat transfer and pressure drop at supercritical pressures. His latest heat-transfer correlation, developed together with his students, for supercritical water flowing in tubes is currently the most accurate one when compared to other correlations developed within the last 50 years. The proposed research, which will include analytical, numerical, Computational Fluid Dynamics (CFD) and experimental work, is based on his extensive expertise on properties and heat-transfer specifics of supercritical water, carbon dioxide, helium and freons and various industrial applications of these fluids including in Generation IV reactors. The objective of this research program is to broaden our knowledge of the fundamental behaviour and various phenomena in supercritical fluids and develop a scientific foundation for understanding parameters that govern behavior of these fluids.