Motion of Nanofluid Droplets through Immiscible Quiescent Liquid: An Experimental Study
2020
Dhindsa, Aarsee | Wanchoo, Ravinder K. | Toor, Amrit P.
Motion of droplets in a liquid–liquid extraction column is of importance for many industrial processes. This study aims at evaluation of hydrodynamic behavior of a nanofluid particle moving through an immiscible liquid. Toluene-based nanofluids were used as referral systems in this study. Nanoparticles of ZnO, Al₂O₃, SiO₂, and TiO₂ have been used to synthesize stable nanofluids. The experiments were carried out using different concentrations of nanoparticles to study the variation in terminal velocity, drag coefficient, and eccentricity of the nanofluid droplet. Observations show enhancement in terminal velocity and reduction in drag coefficient of the droplets, for all nanofluids up to optimum concentration of nanoparticles. With the increase in the concentration of nanofluids beyond the optimum concentration, the droplet terminal velocity decreases and drag coefficient increases due to deformation in shape and an increase in oscillation that could be due to nanoparticle aggregation in the nanofluid. The eccentricity of nanofluid droplets was observed to decrease till optimum concentration, and thereafter it exhibited an increasing trend. Increase in fluid droplet terminal velocity and reduction in drag coefficient in the presence of nanoparticles could be attributed to increase in internal circulation of the droplet due to the presence of micro convection and Brownian motion that leads to reduction in interfacial viscosity and drag and hence leads to increase in droplet velocity. Based on the observed data, an experimental correlation is proposed for the determination of nanofluid particle terminal velocity and drag coefficient. The correlation predictions are in good agreement with observed data.
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