Experimental investigation of heat transport in inhomogeneous bubbly flow

Biljana Gvozdić, On Yu Dung, Elise Alméras, Dennis P.M. van Gils, Detlef Lohse, Sander G. Huisman*, Chao Sun (Corresponding Author)

*Corresponding author for this work

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Abstract

In this work we study the heat transport in inhomogeneous bubbly flow. The experiments were performed in a rectangular bubble column heated from one side wall and cooled from the other, with millimetric bubbles introduced through one half of the injection section (close to the hot wall or close to the cold wall). We characterise the global heat transport while varying two parameters: the gas volume fraction α=0.4–5.1%, and the Rayleigh number RaH=4×109-2.2×1010. As captured by imaging and characterised using Laser Doppler Anemometry (LDA), different flow regimes occur with increasing gas flow rates. In the generated inhomogeneous bubbly flow there are three main contributions to the mixing: (i) transport by the buoyancy driven recirculation, (ii) bubble induced turbulence (BIT) and (iii) shear-induced turbulence (SIT). The strength of these contributions and their interplay depends on the gas volume fraction which is reflected in the measured heat transport enhancement. We compare our results with the findings for heat transport in homogeneous bubbly flow from Gvozdić et al. (2018). We find that for the lower gas volume fractions (α<4%), inhomogeneous bubbly injection results in better heat transport due to induced large-scale circulation. In contrast, for α>4%, when the contribution of SIT becomes stronger, but so does the competition between all three contributions, the homogeneous injection is more efficient.

Original languageEnglish
Pages (from-to)260-267
Number of pages8
JournalChemical engineering science
Volume198
Early online date27 Sep 2018
DOIs
Publication statusPublished - 28 Apr 2019

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Keywords

  • UT-Hybrid-D
  • Bubbly flows
  • Experiments
  • Heat transfer
  • Bubble column

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