Prof. Nivedita Gupta's Talk

Jan 05, 2017 - 17:00

Jan 05, 2017 - 18:00

Rm. No. 118 Ground floor Chemical Engg. Dept.

Seminars

Prof. Nivedita Gupta University of New Hampshire

Abstract: The flow of droplets in confined channels is common in a variety of applications including polymer and emulsion processing as well as oil recovery from porous materials. More recently droplets in microfluidic devices have evolved as a means to conduct chemical reactions in small controlled volumes that can be manipulated easily. In the first part of my talk I will present results for the steady flow of droplets in straight cylindrical channels and their transient response to a sudden expansion in the channel diameter. I will consider the effects of inertia as well as the presence of surfactants on the drop dynamics. Increasing the Reynolds number is seen to cause non-monotonic trends in the drop deformation velocity and extra pressure loss across the channel. Parameters such as the drop viscosity and presence of surfactants were seen to have smaller effects when the Reynolds number became large. The transient deformation of drops moving through expansions depended strongly on the shape of the drop upstream of the expansion. The inclusion of inertial effects caused increases in the transient deformation as well as oscillations as the drops relaxed back into their steady shape. In the second part of the talk I will discuss some of our experimental results on the interphase synthesis of zinc oxide nanoparticles in droplets in a channel. Conducting the synthesis reaction inside droplets of controlled size offers several advantages such as eliminating temperature and concentration gradients inside the reactor as well as preventing reactor fouling. The technique produces zinc oxide nanoparticles with a narrow particle size distribution as compared to a batch reactor. Spherical as well as plate-like shapes of zinc-oxide nanoparticles are seen for the ranges of parameters studied. The size and morphology of the nanoparticles is shown to be easily controlled by varying reagent concentrations reaction temperature and residence time.Bio: Dr. Nivedita Gupta is a Professor in the Department of Chemical Engineering at the University of New Hampshire. She received a B. Tech. in Chemical Engineering from IIT Bombay in 1993 and Ph.D. in Chemical Engineering from Pennsylvania State University in 1999. Dr. Gupta joined the University of New Hampshire in 2002 after completing postdoctoral research at Johns Hopkins University. Her research interests include interfacial flows surfactants effects and microfluidics. Note: Attendance is mandatory for those enrolled in CL 704.