Influence of wall friction on flow regimes and scale-up of counter-current swirl spray dryers

Victor Francia, Luis Martín, Andrew E. Bayly, Mark J. H. Simmons

Research output: Contribution to journalArticle

11 Citations (Scopus)
23 Downloads (Pure)

Abstract

The structure of the vortex flow in swirl spray dryers is investigated after having fouled the walls with deposits typical of detergent manufacture. The range of Re and swirl intensity Ω characteristic of industry are studied using three counter-current units of varying scale and design. The friction with the deposits increases the flow turbulence kinetic energy and causes a drastic attenuation of the swirl and as a result, the vortex breaks down in the chamber forming recirculation regions (i.e. areas of reverse flow). Three flow regimes (1) no recirculation, (2) central and (3) annular recirculation have been identified depending on the swirl intensity. New control and scale up strategies are proposed for swirl dryers based in predicting the decay and the flow regime using the unit geometry (i.e. initial swirl intensity Ωi) and experimental decay rates function of the coverage and thickness of deposits. The impact in design and numerical modelling must be stressed. Adequate prediction of the swirl is vital to study fouling and recirculation, which surely play an important part in the dispersion and aggregation of the solid phase. Current models have no means to replicate these phenomena, and yet, in this case neglecting the deposits and assuming smooth walls would result in (a) over-prediction of swirl velocity up to 40-186% (b) under-prediction of turbulent kinetic energy up to 67-85% and (c) failure to recognise recirculation areas.

Original languageEnglish
Pages (from-to)399-413
Number of pages15
JournalChemical Engineering Science
Volume134
DOIs
Publication statusPublished - 29 Sep 2015

Keywords

  • Recirculation
  • Roughness
  • Scale up
  • Spray drying
  • Swirl decay
  • Vortex flow

ASJC Scopus subject areas

  • Chemistry(all)
  • Chemical Engineering(all)
  • Industrial and Manufacturing Engineering

Fingerprint Dive into the research topics of 'Influence of wall friction on flow regimes and scale-up of counter-current swirl spray dryers'. Together they form a unique fingerprint.

  • Cite this