Hydrodynamics of gas/shear-thinning fluid flowing in a co-flow microchannel

Abstract

Background

Gas-liquid flow hydrodynamics are one of crucial roles in enhancing the interphase transport and reaction properties in microchannel reactors.

Methods

The hydrodynamics of gas-liquid flow in a co-flow microchannel with shear-thinning fluid were numerically investigated using a coupled level-set and volume-of-fluid method by considering the rheological characteristics of the fluid. The reliability of the numerical approach is validated through comparing the calculated liquid film thickness with film thickness in previous work quantitatively. The influences of liquid phase type, carboxymethylcellulose (CMC) solution and surfactant (SDS) concentrations on flow pattern and film thickness are elucidated respectively.

Significant findings

Five flow patterns, i.e., bubbly flow, Taylor flow, Taylor annular flow, annular flow, and churn flow, were intuitively identified in a broad range of liquid phases including water, CMC solution, and polyacrylamide (PAM) solution, and a fundamental flow pattern map has been constructed using the Weber numbers for two phases. The results indicate that the proportions occupied by bubbly flow and churn flow expand significantly whereas the areas associated with other patterns shrink in both non-Newtonian fluids compared to water. The similar transitions in flow pattern are enhanced overall by increasing CMC and SDS concentrations. The film thickness always increases linearly with capillary number in all fluids. The maximum film thickness exists in the most contaminated CMC solutions by SDS, whereas the minimum one in water. Finally, a novel scaling law of film thickness in a co-flow microchannel with shear-thinning liquids is developed and has satisfactory accuracy by comparing with the literature predictions.