Modeling and Experimental Investigation of the Hydrodynamics and Mass transfer of Nanofluid Single dro‎p in the Liquid-Liquid Extraction

6/17/2019 12:00:00 AM

Experimental investigation of the NP’s effects on the hydrodynamics and the mass transfer of the single drop system has been considered in the present study. The hydrodynamics and the mass transfer of LLE single drop system have been investigated using the CFD. In the hydrodynamic stage, the three standard LLE systems have been simulated using the VOF with the two surface tension models of CSF and CSS in the spherical, circulating and oscillating regimes. With the change of the surface tension model from the CSF to the CSS, the relative errors have reduced due to the reduction of the parasitic current effects. The maximum reduction in absolute average relative error was from 9.88 to 3.63% in the toluene/water system with maximum parasitic currents. In the further simulations, the SiO2 NP’s effects on the hydrodynamics of toluene /water system have been investigated, reporting an insignificant effect of NPs on the hydrodynamics, which was also previously approved by the experimental observations. In order to reduce the computational time, the moving reference frame algorithm was developed in Fluent software in the parallel processing form. The hydrodynamic model has been used in different LLE systems over the wide range of the Re number from 16 to 1600, the Weber of 0.04 to 14, the Eötvös of 0.02 to 23, the Capillary of 0.001 to 0.05 and the Morton of 1.9×10-11 to 1.2×10-6. From the hydrodynamic simulations, the new correlations of terminal velocity have been developed using the Genetic algorithm. In the mass transfer stage, the mass transfer codes have been supplemented to the Fluent software in the single equation form. After the verification, the mass transfer model has been used over the range of the Re number from 3 to 7, the Capillary of 0.05 to 0.26, the Eötvös of 0.4 to 5 and the Schmidt of 5×104 to 2×105. The Mass transfer model has been used in the cases of Marangoni convection effects and chemical reaction state. Marangoni model showed a good degree of verification in the concentration range of 7.5 to 30 g/L. In the experimental stage, the effects of hydrophilic SiO2 NPs have been investigated on the hydrodynamic and mass transfer performance of butanol-succinic acid-water in the single drop system over the Re number range of 81 to 206, the Weber of 2 to 8 , the capillary of 0.03, the Eötvös of 1.9 and the Schmidt of 1.52 ×104. The experimental observations showed no considerable effects of NPs on the hydrodynamics using an image processing tool. In the mass transfer investigations, the presence of hydrophilic NPs caused the average reduction of about 25.76 percent and the maximum deterioration of about 53.84 percent in the mass transfer coefficient. The possible reasons for the mass transfer deterioration are the free volume reduction, the tortuosity effects and the relative saturation of interfacial area from the NPs. A new overall mass transfer coefficient correlation and a correlation for the effective diffusivity in the presence of NPs have been developed. The new form of the overall mass transfer coefficient can be used in any LLE system with the resistances in two phases in the presence of NPs. In the next CFD modeling phase, the developed mass transfer model has been used in the butanol- succinic acid-water system, representing the good agreements with the experimental data.