| Summary: | 碩士 === 國立中央大學 === 化學工程與材料工程學系 === 104 === The information of vapor pressure of pure substances and their mixtures is crucial in the field of chemical engineering because these data are necessary for the design and optimization of chemical engineering processes. Recently, the Peng-Robinson + COSMOSAC equation of state has been developed to provide reliable estimation of thermophysical properties and fluid phase equilibria, such as critical properties and vapor pressures of pure fluids and vapor-liquid and liquid-liquid equilibria of mixtures. This model, based on solvation theory and the COSMO-SAC model, utilizes results from quantum mechanical and COSMO solvation calculations to determine energy parameter and volume parameter in the Peng-Robinson equation of state. Thus, it theoretically can be used to estimate thermodynamic properties for all organic substances without issues of missing parameters.
In this study, the Peng-Robinson + COSMOSAC equation of state is modified to improve its accuracy in predicting the vapor pressure of pure substances. The temperature dependence of the dispersion contribution is revised to provide better vapor pressure prediction without introducing new adjustable parameters, especially at lower temperature region (temperature between the triple point temperature and normal boiling point of a substances). A total of 1125 organic substances are considered in this work. The overall average logarithmic deviation for pressure (ALD-P) is 0.210 from the modified version, which is greatly improved while comparing to that from the original version (ALD-P = 0.234). This model is particularly useful when no experimental data is available in literature.
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