Effects of the gas phase molecular weight and bubble size on effervescent atomization

Azizur Rahaman, M. Balzan, T. Heidrick, B. A. Fleck

Research output: Contribution to journalArticle

17 Citations (Scopus)

Abstract

The effervescent atomization from an industrial Coker feed nozzle is compared for two different gas densities (air and mixed gas of 81.4. vol.% helium/18.6. vol.% nitrogen) at equivalent operating temperatures. The application is to observe the similarity of lab tests using air at 20°C to the industrial process using steam at 300-400°C. The effects of operating conditions, such as gas to liquid mass ratio, mixing pressure and void fraction on the flow regime, bubble size, and droplet size distribution were also examined in this study. The experiments were performed using mixtures of water with air or mixed gas, which resulted in gas to liquid mass ratios ranging from 1% to 4%.Stroboscopic back scattered imagery (SBSI) indicates that the average bubble size inside the nozzle conduit is similar when air and water are used as the process fluids, when compared to the case when mixed gas and water are used as the process fluids. Under similar conditions, the Phase Doppler Particle Anemometer (PDPA) data indicate that the droplet size in the spray is similar when using either mixed gas or air as the atomization gas.Experimental results obtained by high-speed video shadowgraphy (HSVS) indicate that the flow pattern inside the nozzle feeding conduit was slug flow with a tendency to attain annular flow with increased air to liquid mass ratios. Thus, from the experimental results it is evident that the smaller molecular weight of the mixed gas versus air (8.4 versus 29) does not significantly reduce the bubble (<±10% difference) and droplet size (<±1.5% difference), indicating a weak dependence of the gas phase density on two-phase atomization. This confirms that laboratory experiments on effervescent nozzles using air have reliable similarity to systems that use high temperature steam for the gas phase.

Original languageEnglish
Pages (from-to)35-52
Number of pages18
JournalInternational Journal of Multiphase Flow
Volume38
Issue number1
DOIs
Publication statusPublished - Jan 2012
Externally publishedYes

Fingerprint

atomizing
Atomization
molecular weight
bubbles
Gases
Molecular weight
vapor phases
air
nozzles
gases
Air
mass ratios
Nozzles
steam
Steam
Bubbles (in fluids)
liquids
gas atomization
Water
water

Keywords

  • Bubble size
  • Droplet size
  • Flow patterns
  • High speed video shadowgraph
  • Horizontal nozzle
  • Phase Doppler Particle Anemometer
  • Stroboscopic back scattered imagery
  • Two phase atomization

ASJC Scopus subject areas

  • Mechanical Engineering
  • Physics and Astronomy(all)
  • Fluid Flow and Transfer Processes

Cite this

Effects of the gas phase molecular weight and bubble size on effervescent atomization. / Rahaman, Azizur; Balzan, M.; Heidrick, T.; Fleck, B. A.

In: International Journal of Multiphase Flow, Vol. 38, No. 1, 01.2012, p. 35-52.

Research output: Contribution to journalArticle

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