Liquid-phase mass transfer in high-pressure systems with a supercritical and a liquid phase |
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Authors: | C. A. Lockemann E. -U. Schilünder |
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Affiliation: | (1) Institut für Thermische Verfahrenstechnik, Universität Karlsruhe, Kaiserstrasse 12, D-76128 Karlsruhe, Germany |
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Abstract: | Liquid-phase diffusion coefficients and mass-transfer coefficients were measured in binary two-phase systems at high pressures. Both were determined from the rates of absorption of the gaseous component into the liquid. Diffusion coefficients were measured by observing unsteady-state diffusion into a sell) i infinite liquid phase and fitting transient counterdiffusion mass-flow rates to the visually determined change of the position of the interface between the liquid and the supercritical phase. Mass-transfer coefficients in the liquid phase were determined from the absorption rate of the gaseous component into a falling liquid film of known flow and physical properties. Experiments were performed with the binary systems carbon dioxide-oleic acid, carbon dioxide -methyl myristate, and carbon dioxide-methyl palmitate. Liquid-phase diffusion coefficients rise significantly with concentration as viscosity decreases. Temperature also has a strong effect on diffusivities. Experimental mass-transfer coefficients in nearly saturated liquids agree well with calculations for falling films with known properties, whereas far from equilibrium, Marangoni convection greatly enhances mass-transfer rates. Close to the critical point of the binary system at a given temperature, a sharp decline of the mass-transfer coefficient is observed. |
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Keywords: | diffusion coefficient falling film high-pressure system liquid phase mass-transfer coefficient supercritical phase |
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