Gas–liquid–liquid three-phase flow pattern and pressure drop in a microfluidic chip: similarities with gas–liquid/liquid–liquid flows

Abstract

We report a three-phase slug flow and a parallel-slug flow as two major flow patterns found under the nitrogen-decane-water flow through a glass microfluidic chip which features a long microchannel with a hydraulic diameter of 98 μm connected to a cross-flow mixer. The three-phase slug flow pattern is characterized by a flow of decane droplets containing single elongated nitrogen bubbles, which are separated by water slugs. This flow pattern was observed at a superficial velocity of decane (in the range of about 0.6 to 10 mm s(-1)) typically lower than that of water for a given superficial gas velocity in the range of 30 to 91 mm s(-1). The parallel-slug flow pattern is characterized by a continuous water flow in one part of the channel cross section and a parallel flow of decane with dispersed nitrogen bubbles in the adjacent part of the channel cross section, which was observed at a superficial velocity of decane (in the range of about 2.5 to 40 mm s(-1)) typically higher than that of water for each given superficial gas velocity. The three-phase slug flow can be seen as a superimposition of both decane-water and nitrogen-decane slug flows observed in the chip when the flow of the third phase (viz. nitrogen or water, respectively) was set at zero. The parallel-slug flow can be seen as a superimposition of the decane-water parallel flow and the nitrogen-decane slug flow observed in the chip under the corresponding two-phase flow conditions. In case of small capillary numbers (Ca ≪ 0.1) and Weber numbers (We ≪ 1), the developed two-phase pressure drop model under a slug flow has been extended to obtain a three-phase slug flow model in which the 'nitrogen-in-decane' droplet is assumed as a pseudo-homogeneous droplet with an effective viscosity. The parallel flow and slug flow pressure drop models have been combined to obtain a parallel-slug flow model. The obtained models describe the experimental pressure drop with standard deviations of 8% and 12% for the three-phase slug flow and parallel-slug flow, respectively. An example is given to illustrate the model uses in designing bifurcated microchannels that split the three-phase slug flow for high-throughput processing.

On the leakage flow around gas bubbles in slug flow in a microchannel

“…All experiments were conducted at atmosphere pressure and room temperature. According to the pressure drop model proposed by Yue et al, 36 the pressure drop over the entire microchannel reactor varied from 57.3 Pa to 1314.6 Pa, so the compressibility effect of gas could be neglected.…”

Liter-scale production of uniform gas bubbles via parallelization of flow-focusing generators

“…Although we do not fully understand the exact mechanisms by which each of these factors affects the bubble size uniformity, we believe that the resistance of the FFG ( R f ) likely depends very sensitively on these parameters (bubble size, capillary number, and viscosity ratio) because there is a two phase flow involving bubble suspensions in the FFGs and the dispersed phase is compressible (unlike liquid emulsions). 35–37 Thus, fluctuations in the size of orifices and channels of FFGs that result from the fabrication of highly parallelized large-scale devices can lead to significant variations in the R f , possibly causing different bubble break-up dynamics in different FFGs, leading to the formation of polydisperse gas bubbles.…”

Coaxial Flow Contactors as Alternative to Double T‐Contactors for Triphasic Slug Flow Generation

“…Rajesh and Buwa, Yue as well as Wang et al. studied the flow regimes in triphasic flows and generated flow maps for stable regions . Pressure drop was studied by Ladosz et al.…”

“…and Yue et al. , . The usability for extraction in multiphase flows was studied by Assmann et al., Aoki et al.…”

“…In literature, a PDI below 5 % is considered as regular flow and can be achieved with most contactor designs for biphasic flows, gas‐liquid and liquid‐liquid .…”