Transport and reaction in microscale segmented gas-liquid flow

Area of Science:

• * Multiphase flow dynamics in microfluidics.
• * Chemical reaction engineering.
• * Nanoparticle synthesis.

Background:

• * Microfluidic systems offer precise control over chemical reactions.
• * Understanding gas-liquid flow is crucial for optimizing reaction efficiency and product yield.
• * Low superficial velocities are relevant for reactions requiring extended residence times.

Purpose of the Study:

• * To characterize microscale segmented gas-liquid flow at low velocities.
• * To quantify recirculation and mixing in different channel geometries.
• * To develop and apply a novel method for measuring residence time distributions (RTDs).

Main Methods:

• * Micro particle image velocimetry (microPIV) and fluorescence microscopy.
• * Fabrication of poly(dimethylsiloxane) (PDMS) microfluidic channels via soft lithography.
• * Piezoelectrically activated flow injection for RTD measurements.

Main Results:

• * Recirculation patterns and symmetry loss quantified in straight and meandering channels.
• * Surface roughness and gas compressibility impact symmetry and enhance centerline mixing.
• * Meandering channels accelerate mixing through altered recirculation patterns.
• * Segmented flows exhibit narrower liquid phase RTDs compared to single-phase flows.

Conclusions:

• * Microscale segmented gas-liquid flow enhances mixing and provides narrow RTDs.
• * These characteristics are beneficial for liquid mixing and sol-gel synthesis of nanoparticles.
• * The findings contribute to the design and optimization of microfluidic reactors.