Axial dispersion in segmented gas-liquid flow: Effects of alternating channel curvature

Abstract

The effects of channel curvature on the axial dispersion in segmented gas-liquid flows are studied computationally in a two-dimensional setting using a finite-volume/front-tracking method. Passive tracer particles are used to visualize and quantify the axial dispersion. The molecular diffusion is modeled by random walk of tracer particles. It is found that there is significant axial dispersion in serpentine channels even in the absence of molecular diffusion. The lubricating thin liquid layer that persists on the wall of a straight channel is periodically broken in the serpentine channel leading to enhanced axial dispersion. It is also found that the axial dispersion is always larger in the serpentine channel than that in the straight channel but the effects of channel curvature are more pronounced at high Peclet numbers, i.e., PeϾ 10 4 . A model is proposed based on the difference between the liquid film thicknesses on the inner and outer side of the bend in the limit as Pe→ ϱ. Good agreement is found between the computational results and the model when the liquid slug is well mixed by the chaotic advection.

CO2 Absorption by Liquid Films under Taylor Flow in Serpentine Minichannels

“…According to the twofilm theory, the concentration of CO 2 in the main body of the liquid slug is obviously reduced due to the enhancement of the turbulence degree of the fluid by the secondary flow. Thus, the mixing of the newly added solute CO 2 in the main body of the liquid slug is consistent with the mixing law of the solute in the liquid slug under the secondary flow proposed by Muradoglu et al 26 Eventually, the shrinking rate of the bubble can be expressed by i k j j j j j y…”

“…where A s is the area of the liquid slug and A h is the area of the liquid layer that leaks through the outer film in the halfperiod. 26 Period refers to the periodic change of the liquid film when bubbles pass through the bent channel, as shown in Figure 3C. In the experiment, the liquid film undergoes a similar change for four consecutive curves, which is defined as a bubble change period.…”

“…It is found that due to the better radial mixing and flow pattern of the curved channel, the mass transfer rate increases sharply. 24 Muradoglu et al 26 shows by simulation that the circulation in the liquid slug under Taylor flow breaks due to the secondary flow in the curved channel. Kovats et al 27 found that the gas− liquid mass transfer in the first cycle of the spiral channel was intensified due to the high impact of Dean vortex on mass transfer.…”

“…32 Under the influence of the curved channel on mass transfer and bubble shape, it is more difficult to calculate the bubble volume. Muradoglu et al 26 found the leakage of liquid from liquid films around bubbles under Taylor flow in a curved microchannel by simulation. In general, due to the secondary flow, it is more difficult to obtain the volume of the bubble during mass transfer, leading to the lag of the study on mass transfer with high-viscosity fluids.…”

Numerical modeling of multiphase flows in microfluidics and micro process engineering: a review of methods and applications

“…The authors identified three characteristic dispersion regimes, depending on the Peclet number. In a follow-up paper, Muradoglu (2010) investigated the effects of alternating channel curvature and found that the axial dispersion in a serpentine channel is enhanced as compared with a straight one. Wörner et al (2007) evaluated the diffusion-free liquid phase residence time distribution in Taylor flow through a square minichannel from 3D PLIC-VOF computations.…”