Browsing by Subject "Mixtures"
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Item Prediction of bulk and interfacial thermodynamic properties of polar mixtures by statistical associating fluid theory(2003) Ayyalasomayajula, Padmakar S.; Sharma, Mukul M.A Statistical Associating Fluid Theory (SAFT) for multi-component mixtures has been implemented in conjunction with a phase-stability and flash algorithm. The model has been extensively tested for various non-associating and associating mixtures and comparisons are made with the Peng-Robinson equation of state. Both Peng-Robinson and SAFT are equally suitable for simple nonassociating mixtures but SAFT clearly is more accurate when polar mixtures are modeled. The phase behavior of methanol-water-hydrocarbon mixtures is studied with the SAFT equation and the Peng-Robinson equation and comparisons are made with experimental liquid dropout data. The SAFT equation of state is shown to give better predictions for methanol-hydrocarbon and methanol-waterhydrocarbon mixtures over a range of pressures and compositions. The effect of methanol concentration and temperature on dew-point to bubble-point transition of a gas-condensate mixture is studied with the SAFT equation of state. The SAFT equation of state is coupled with the Gradient Theory to calculate the interfacial tension of pure components as well as multi-component mixtures. Pure component interaction parameters (cii) for the calculation of interfacial tension with the SAFT equation have been introduced. A mixing interaction coefficient for interfaces (mij) has been defined to satisfactorily predict the interfacial tension of certain mixtures such as water-methanol and waterethanol systems. The effect of temperature and pressure is studied for a methanewater mixture and it is shown that no further adjustable parameters need to be introduced to accurately predict the interfacial tension over a range of temperatures and pressures. Finally, the SAFT equation of state has also been integrated in to the reservoir simulator (UTCOMP) so as to be able to do flow simulations of complex polar mixtures. The flow simulations with SAFT have also been compared with experimental core flood studies and it is shown that both the PR and the SAFT equation give reasonable agreement with experimental data. However, it is shown that the SAFT based model predictions are slightly better during the methanol injection stage of the experiment. However, significantly larger computational time discourages the use of SAFT for such flow simulations.Item Prediction of coexistence vapor-liquid densities for substances and mixtures(Texas Tech University, 2005-05) Soefajin, Andreas; Akanni, Lawal; Adisoemarta, Paulus S.Knowledge of the critical state is important in any study of phase behavior; therefore, the applications of critical state prediction methods can be found in many areas of the petroleum and chemical industries. However, the vapor-liquid and volumetric computations for reservoir fluid systems in the retrograde and near-critical regions still remain a challenge. As a precursor in establishing a predictive equation of state for compositional reservoir processes, a previously established four-parameter cubic equation of state reported by Lawal-Lake-Silberberg (LLS) is used to predict orthobaric densities, second virial coefficient and critical volumes of pure substances (hydrocarbon, non-hydrocarbon, polar and non-polar fluids). The prediction results are generally within 0.5% of the experimental measurements. A framework of the attractive temperature function is established for two parameter (Peng-Robinson and Soave-Redlich-Kwong) and four parameter LLS equations of state. The temperature function is demonstrated to be internally consistent with the critical behavior of fluids at sub- and super-critical conditions and the function does not suffer the difficulty encountered with Soave-type of temperature function which hitherto has been major source of research in equations of state development. An analysis of the thermodynamic constraint criteria of the critical state of pure substances and binary mixtures is used to establish a theoretical expression for the van der Waals critical point. The theoretical expression for the van der Waals criticality is validated by the prediction results of binary critical volumes of asymmetric substances and mixtures. This project offers an insight to the phase behavior of ternary and multicomponent mixtures and the challenge for the future work is to apply this robust method to the near-critical flash routine in ternary and multicomponent systems.Item Selective laser melting of elemental aluminum silicon mixtures(2016-12) Roberts, Christopher Eli; Bourell, David LeeAdditive manufacturing technologies have generated increasing interest by public, government, and academic institutions alike. While past research has increased part quality, build speed, and process reliability, there remains few materials which can be processed through selective laser melting (SLM). Historically, metal feedstock for powder bed fusion processes have been pre-alloyed, near-eutectic grades similar to traditional casting alloys. This thesis discusses an alternative processing route utilizing elemental mixtures for off-eutectic, difficult-to-processes alloys which exhibit a large freezing range and solidification shrinkage such as that found in many wrought aluminum alloys. One such alloy is aluminum 6061. This material is of great commercial interest due to its widespread use within the traditional manufacturing industry, successful prior certification in aerospace industries, and good mechanical properties. Since AA6061 consists of multiple elements, a representative system of aluminum and silicon was utilized for consideration in this thesis. A powder feedstock of commercially pure aluminum and silicon was prepared and processed through SLM. Samples were then heat treated to homogenize the silicon aluminum matrix. Metallographic analysis was performed throughout the experiment to determine the underlying materials processes. Dense parts without solidification cracking were produced and silicon dissolution into the aluminum matrix was verified using scanning electron microscopy (SEM) and energy dispersive x-ray spectroscopy (EDS). The combined-powder process that is outlined could be expanded to other material systems which are not compatible with current additive manufacturing technologies. An overview of the theory behind the use of elemental mixtures as well as the results from the aluminum silicon (Al-Si) mixture are presented. Future work needed to be accomplished and potential challenges associated with this processing route are also discussed.