Axial dispersion in curved channels in the presence of pulsating flow

Gleb Valitov, Damiano Rossi, Chris Price, Asterios Gavriilidis, Luca Mazzei

Research output: Contribution to journalArticlepeer-review

Abstract

A narrow residence time distribution (RTD) is desirable in several chemical engineering processes. However, in systems operating at low Reynolds number, axial dispersion can be significant. To lower it, we utilised two mixing approaches: secondary flow achieved with curved geometries and oscillatory variation of the flow rate. We investigated their combined effect on axial dispersion in millifluidic channels with three geometries: straight tube, helically coiled tube (HCT) and coiled flow inverter (CFI). We studied the influence on axial dispersion of two key parameters of pulsating flows: amplitude and frequency of pulsation; in dimensionless form, these are expressed via the amplitude ratio and Strouhal number, respectively. For unsteady flow, we performed numerical simulations to characterise mixing. The results indicate that pulsation enhances radial mixing significantly. Our experimental studies show that axial dispersion is lower in the presence of pulsation, and increasing amplitude and/or frequency has a positive effect. For the same amplitude ratio and Strouhal number, axial dispersion decreases more in the CFIs than in the HCTs. Comparing two extremes, the straight capillary with steady flow (no RTD enhancement) and the CFI with pulsation (lowest axial dispersion achieved in our work), we observed a 10-fold reduction in the axial dispersion number.

Original languageEnglish
Article number108629
Number of pages12
JournalChemical Engineering and Processing - Process Intensification
Volume180
Early online date23 Aug 2022
DOIs
Publication statusPublished - 31 Oct 2022

Keywords

  • axial dispersion, residence time distribution
  • coiled flow inverter
  • helically coiled tube
  • microfluidics
  • oscillatory flow

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