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Experimental and Numerical Investigation on the Single Drop Liquid-liquid Mass Transfer in the Presence of Magnetic Nano-particles (Ferrofluids) and Magnetic Field

Memari, Mohammad | 2018

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 51789 (06)
  4. University: Sharif University of Technology
  5. Department: Chemical and Petroleum Engineering
  6. Advisor(s): Molaie Dehkordi, Asghar; Seif Kordi, Ali Akbar
  7. Abstract:
  8. The main objective of the present work was to improve the turbulence in single drops using ferrofluids (magnetic nanoparticles) in the presence of uniform and oscillating magnetic fields. In this regard, magnetite nanoparticles ($\mathrm{Fe_3O_4}$) were synthesized by co-precipitation method, characterized using DLS, FT-IR, XRD, VSM, and TEM, and their stability was checked by UV-Vis. The obtained results indicate the proper synthesis of nanoparticles with a mean diameter of about 20 nm and by coating their surfaces by silane that were well stabilized in the base fluid. In the numerical section, the governing equations of transport phenomena for a single drop containing magnetic fluids were presented and solved by a finite element method (FEM). Numerical results were validated against experimental data. The discrepancy between the numerical results and the experimental data were quite small and the numerical solution was acceptable. Numerical results show that the effect of uniform and oscillating magnetic fields on the hydrodynamic behavior and mass transfer of single drops can be significant for the large intensity of magnetic fields and the turbulence in the drops increases. In addition, liquid−liquid equilibrium data including density, viscosity, and interfacial tension of toluene−acetic acid−water were obtained at 298.15 K. Correlations for density, viscosity, and interfacial tension with a precision of 1% were derived and presented. The experimental data obtained in this work and those in the literature were satisfactorily correlated using both the nonrandom two-liquid (NRTL) and the universal quasi-chemical (UNIQUAC) activity coefficient models. The root-mean-square deviation (RMSD) values were less than 3.58% for the thermodynamic models and the model predictions show acceptable agreement. Moreover, hydrodynamic and mass transfer experimental runs were designed and carried out and the effect of nanoparticles in the presence and absence of magnetic fields such as uniform and oscillating magnetic fields were studied. The maximum enhancement in the mass-transfer rate was obtained at low concentrations of nanoparticles (a mass fraction of about 0.01%) and in the high intensity of magnetic field for a uniform and oscillating magnetic fields so that the maximum enhancement in mass transfer for the oscillating magnetic fields was obtained at a mass fraction of nanoparticles about 0.01% and a high intensity of the magnetic field about 170 G where this maximum enhancement was about 70%. Furthermore, it was found that the mass-transfer rate decreases for large concentrations of nanoparticles with a reduction of about 60%
  9. Keywords:
  10. Liquid-Liquid Mass Transfer ; Ferrofluid ; Uniform Magnetic Field ; Nanoparticle Synthesis ; Experimental Modeling ; Magnetic Nanodot ; Oscillating Magnetic Field ; Single Drop Technique

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