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Calculation of Interfacial Tension in Water-Methane System at High Pressures Using Molecular Simulation

Salami, Hossein | 2014

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 45810 (06)
  4. University: Sharif University of Technology
  5. Department: Chemical and Petroleum Engineering
  6. Advisor(s): Ghotbi, Cyrus; Taghikhani, Vahid; Robert, Marc
  7. Abstract:
  8. Interfacial tension has wide application in surface engineering and specially oil and gas industry. One has to do work to transfer a molecule from bulk to the surface of a fluid. The amount of this work is proportional to Interfacial tension.Molecular simulation is a fundumental approach for calculating the thermophisycal properties of matter such asInterfacial tension.In this thesis we have investigated the effect of pressure and temperature on surface tension of pure water and interfacial tension of Water-Methane system. The TIP4P potential model was used for Water molecules and OPLS for Methane molecules. In the first part, Water heat capacity and Methane density were calculated for ensuring the validity of potential models. For calculation of interfacial tension, we developed a vapor and liquid phase separately and then let them to reach the equilibrium state toghether in a new simulation cell. Finally, we have calculated the tension between these phases using a virial formula for Interfacial tension. The simulation results were obtained for temperatures 300, 400 and 500K and pressures low, intermediate and high (related to the number of Methane molecules in gas phase). Comparing the simulation results to the experimental data shows that the error in predicted interfacial tension rises with system pressure which is because of system size and temperature wich is a result of more error in solving the Newtonian equation of motion in higher speeds. Simulation results show the Interfacial tension decreases with pressure and with temperature which is expected from experimental data
  9. Keywords:
  10. Surface Stress ; Molecular Dynamic Simulation ; Interfacial Tension

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