1 research outputs found
Hydrodynamic studies of aqueous two-phase systems in millichannels
Liquid-liquid segmented flows in microchannels have been extensively
investigated in the context of nanoparticle synthesis. The enhanced mixing in
the slugs results in monodispersed particles. Earlier studies have focused on
Organic-Aqueous Systems (OAS). The nanoparticles synthesized in the presence of
organic solutions have limited applications. An alternative green route for the
synthesis can be developed using an Aqueous Two-Phase System (ATPS). These
systems are characterized by interfacial tensions, which are two orders of
magnitude lower than typical organic aqueous systems. In this work, flow
patterns and hydrodynamics of ATPS are investigated as a first step.
Polyethylene glycol -trisodium citrate system was chosen as ATPS. The objective
of this work is to see if any new physics arises in an ATPS system. The low
interfacial tension results in high Capillary numbers (Ca >> 3) in a
microfluidic system. Consequently, the flow observed here is parallel or
core-annular. However, in a millichannel, the capillary number becomes lower
(Ca << 1) for an ATPS system. In this work, experiments were carried out in a
millichannel to span different flow patterns. The pattern formation was
analyzed and classified into three categories, i.e., slug flow (interfacial
tension dominated), transition flow, and core annular flow (inertia dominated).
Flow regime maps based on the Reynolds number, Capillary number, and Weber
number of each phase were found to be qualitatively similar to those of OAS.
Simulations were performed for various interfacial tension values. An
interfacial tension value of 1.25x10-4 N/m was found to yield slug sizes which
fitted well with the experimental data. Film thickness was measured
experimentally and with simulations compared favorably with the correlations
available in the literature for OAS