Multiphase

MULTIPHASE EQUILIBRIA AND THERMODYNAMIC PROPERTIES FOR SIMPLE AND COMPLEX FLUIDS

“Significant progress in phase-equilibrium thermodynamics can be achieved ONLY by increased use of the concepts of molecular physics”

John M. Prausnitz

"If there is no complete agreement between the results of one's work and the experiment, one should not allow oneself to be too discouraged."
Paul Dirac

The study of multiphase equilibria is a subject of interest in thermodynamic modeling. We use different statistical mechanical models to predict multiphase equilibria for various types of mixtures such as gas hydrates, polyelectrolyte solutions with small ions, polarizable Stockmayer fluid, polar and associative mixtures. We use and develop statistical mechanical models to obtain quantitative and qualitative prediction. For quantitative prediction, we are interested in extending these models to practical applications. On the other hand, we use qualitative prediction to explain and understand various types of physical phenomena.

MODELING OF SINGLE AND MIXED GUEST HYDRATES

We use thermodynamic modeling approach to predict the formation conditions of natural gas hydrates. Our approach uses van der Waals-Platteeuw (vdWP) model for the hydrate phase and the SAFT-VR Mie equation of state (EOS) for the vapor and liquid phases. We employ three different association schemes into the SAFT-VR Mie EOS to account for hydrogen bonds among water molecules using square-well (SW), Lennard-Jones (LJ) and Mie potentials.

PHASE BEHAVIOR OF POLYELECTROLYTE SOLUTIONS IN THE PRESENCE OF SMALL IONS

With the collaboration with Dr. Zhen-Gang Wang from Caltech

We use a liquid state theory to predict the phase behavior of salty polyelectrolyte solution. The theory uses TPT1 to account for chain connectivity and excluded volume and mean spherical approximation to account for electrostatic correlation.

MODELING OF POLARIZABLE STOCKMAYER FLUID AND OTHER FLUIDS

We developed a general theory to account for any kind of polarization arising from polar and ions. We applied the theory to study the phase equilibria of polarizable Stockmayer fluid and other polar mixtures. We are working on extending the theory to more complex fluids.

MODELING OF ASSOCIATIVE AND POLAR MIXTURES

Our interest is also extended to study associative and polar mixtures. We obtained quantitative prediction without adjusting any parameters for mixtures. The following figures show some examples. The quantitative perdition was obtained by the focus on understanding the molecular interactions between these molecules.

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VLE of methanol-hexane

VLE of ethanol-pentane

VLE of 2-propanol-water

Excess enthalpy of EG-Aliphatic alcohols

HOW TO CARRY OUT THE MULTIPHASE CALCULATIONS?

The multiphase calculations using statistical mechanical models need reliable and robust method. We developed such a method. The method can be used for VLE, LLE and VLLE.