Supercritical thermophysical properties

Interest in the use of SC solvents as a reaction media is founded upon recent advances in our understanding of their unique thermo-physical and chemical properties. Worthy of special note are those thermophysical properties (6) which can be manipulated as parameters to selectively direct the progress of desirable chemical reactions. These properties include the solvent s dielectric constant (7), ion product (8,9), electrolyte solvent power (10,11), transport properties"[viscosity (12), diffusion coefficients (13) and ion mobilities (14)], hydrogen bonding characteristics (15), and solute-solvent "enhancement factors" (6). All these properties are strongly influenced by the solvent s density P in the supercritical state. 

Franck, E.U. "Thermophysical Properties of Supercritical Fluids with Special Consideration of Aqueous Systems", Fluid Phase Equilib. 1983, 10(2-3), 211-22. 

Due to their peculiar solvent properties, supercritical fluids offer a range of unusual chemical possibilities such as in environmentally benign separation and destruction of hazardous waste, as well as for new materials synthesisd" These intriguing reaction media make it possible to sensitively control reaction rate and selectivity with changes in temperature and pressure. The thermophysical properties of water as well as more than 70 other fluid systems have been formulated and/or compiled by lAPWS and NIST. ... 

Carles P. A brief review of the thermophysical properties of superaitical fluids. J Supercrit Huids 2010 53 2-11. 

BOY Boyer, S.A.E., Klopffer, M.-H., Martin, J., and Grolier, J.-P.E., Supercritical gas-polymer interactions with applications in the petroleum industry. Determination of thermophysical properties, J. Appl. Polym. Sci., 103, 1706, 2007. 

Mann, D., Pioro, I., 2015. Study on specitics of thermophysical properties of supercritical fluids in power engineering apphcations. In Proceedings of the 23rd International Conference on Nuclear Engineering (ICONE-23), May 17—21, Chiba, Japan, Paper 1730, 11 Pages. 

Pioro, L, Mokry, S., 2011. Thermophysical properties at critical and supercritical conditions. In Behniloudi, A. (Ed.), Heat Transfer. Theoretical Analysis, Experimental Investigations and Industrial Systems. INTECH, Rijeka, Croatia, pp. 573—592. Free download from http // www.intechopen.com/books/heat-transfer-theoretical-analysis-experimental-investigations-and-industrial-systems/thermophysical-properties-at-critical-and-supercritical-pressuies. 

Pioro, I., Mokry, S., Draper, S., 2011. Specifics of thermophysical properties and forced-convective heat transfer at critical and supercritical pressures. Reviews in Chemical Engineering 27 (3—4), 191—214. 

Appendix A3 Thermophysical properties of fluids at subcritical and critical/ supercritical conditions ... 

Therefore, the most widely used supercritical fluids as of today and possibly in the future are water, carbon dioxide, helium, and refrigerants. Often, refrigerants, similar to carbon dioxide, are considered as modeling fluids instead of water due to significantly lower critical pressures and temperatures (for example, R-134a Per = 4.0593 MPa Per = 101.06°C), which decreases the complexity and costs of thermal hydraulic experiments. Based on the above mentioned, knowledge of thermophysical properties specifics at critical and supercritical pressures is very important for safe and efficient use of fluids in power and other industries. 

Figs. A3.5—A3.12 show variations in the basic thermophysical properties of water at three subcritical pressures [all (a) figures] (1) 7 MPa—usual operating pressure of boiling water reactors (BWRs) and many Ranldne steam turbine cycles in pressurized water reactor (PWR), BWR, and RBMK NPPs (2) 11 MPa—usual inlet pressure for CANDU reactors and (3) 15 MPa—usual pressure for PWRs and the critical (Per = 22.064 MPa) and four supercritical pressures (P = 25, 30, 35, and 40 MPa) [all (b) figures]. The range of critical and supercritical pressures covers current range... 

It should be noted that thermophysical properties of 121 pure fluids, including water, carbon dioxide, helium, refrigerants, etc. 5 pseudo-pure fluids (such as air) and mixtures with up to 20 components at different pressures and temperatures, including critical and supercritical regions, can be calculated using the NIST REFPROP software (2010), Version 9.1. 

Analysis of profiles shown in Figs. A3.5—A3.12 for subcritical water [figures (a)] and critical/supercritical water [figures (b)] shows similar trends. However, for subait-ical water, there are two different values of any thermophysical property on the saturation line one for liquid and one for vapor (steam). However, for example, at pressure of 7 MPa, values of specific heat of water (5.4025 kJ/kg K) and steam (5.3566 kJ/kg K) can be very close (see Fig. A3.9(a)). Also, it can be clearly seen that pressure has almost negligible effect of liquid properties. Just closer to the saturation line, some small differences can be seen in property profiles at various pressures. 

Supercritical fluids are used intensively in various industries. Therefore, understanding specifics of thermophysical properties and their behavior at critical and supercritical pressures is an important task. Supercritical fluids are considered as single-phase substances in spite of significant variations of all thermophysical properties within critical or pseudocritical regions. Some of these variations in thermophysical properties are similar to those at subcritical pressures during crossing of the saturation line. 

Eq. [A4.4] is applicable for subcritical and supercritical pressures. However, adjustment of this expression to conditions of supercritical pressures, with singlephase dense gas and significant variations in thermophysical properties near the critical and pseudocritical points, was the major task for the researchers and scientists. In general, two major approaches to solve this problem were taken an analytical approach (including numerical approach) and an experimental (empirical) approach. 

Pioro, I., 2014. Application of supercritical pressures in power engineering specifics of thermophysical properties and forced-convective heat transfer. In Anikeev, V., Fan, M. (Eds.), Supercritical Fluid Technology for Energy and Environmental Applications. Elsevier, pp. 201-233. 

Thermophysical properties of gases, liquids, and fluids at supercritical pressures used in publications of Dr. I. Pioro were calculated according to the National Institute of Standards and Technology software (2010) (http //www.nist.gov/srd/nist23.cfm). 

Technical Appendices, which provides readers with additional information and data on current nuclear power reactors and NPPs thermophysical properties of reactor coolants, thermophysical properties of fluids at suhcritical and critical/supercritical pressures, heat transfer and pressure drop in forced convection to fluids at supercritical pressures, world experience in nuclear steam reheat, etc. 

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