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Master of Science in Mechanical Engineering (M.S.M.E.)
Year Degree Awarded
Month Degree Awarded
Carbon Dioxide, Ethanol, Rapid Expansion of Supercritical Solutions, Capillary Flow, Supercritical
Homogenous and separated flow methods have been presented for use in the capillary tube section of the Plasma Rapid Expansion of Supercritical Solutions (PRESS) process using a carbon dioxide and ethanol mixture as the working fluid. Each method was validated against experimental expansion processes using pure carbon dioxide, isobutane, and R-134a. The results have indicated that both the homogenous flow method and the separated flow method produce results within an acceptable margin of error. By accounting for the phase interactions the separated flow method produces more accurate results with mean errors of 8.03%, 4.57%, and 5.77% for carbon dioxide, isobutane, and R-134a, respectively. In comparison, the mean errors of the homogenous method were 8.17%, 5.4%, and 8.55%, respectively. The homogenous and separated flow methods were shown to be statistically and significantly different for 95% confidence, which demonstrates that the accuracy of capillary flow simulation can be increased through the use of the separated flow method. A method to extend the methods for the mixture of carbon dioxide and ethanol was implemented in a limited fashion. Under certain conditions the carbon dioxide and ethanol mixture results in the trivial root problem associated with the cubic compressibility equation. As literature on the subject of the trivial root problem is limited, the expansion process was focused on a region where three real roots exist to the compressibility equation. A simulation of a carbon dioxide and ethanol mixture expansion process was successfully implemented at a low temperature using the homogenous flow method. For validation, a VLE diagram was created for the mixture and compared adequately with experimental results.
David P. Schmidt