Bubble size and air content of wet fibre foams in axial mixing with macro-instabilities

Ahmad Al.Qararah, Tuomo Hjelt, Antti Koponen, Ali Harlin, Jukka Ketoja (Corresponding Author)

Research output: Contribution to journalArticleScientificpeer-review

22 Citations (Scopus)

Abstract

The air content and bubble size distribution in pure foams and in fibre foams were determined in axial mixing for varied rotation speed, liquid surface tension and wood fibre concentration. Onset of flow macro-instabilities was observed at high rotation speeds both with and without fibres. Before the instability, the bubble size decreased and air content increased with increasing rotation speed. After the instability, the air content was not only strongly affected by rotation speed but, interestingly, both the air content and bubble size increased with reduced surface tension. In both regions, the average bubble size could be explained based on the capillary number after the air content was explicitly included in the model. Added fibres reduced the bubble size in the stable mixing region and for low surface tension levels in the unstable mixing region. This was probably caused by increased shear forces due to inertia of fibres breaking up the large bubbles in the foam.
Original languageEnglish
Pages (from-to)1130-1139
Number of pages9
JournalColloids and Surfaces A: Physicochemical and Engineering Aspects
Volume436
DOIs
Publication statusPublished - 2013
MoE publication typeA1 Journal article-refereed

Fingerprint

foams
Macros
Foams
bubbles
fibers
Fibers
air
Surface tension
Air
interfacial tension
liquid surfaces
Wood
inertia
shear
Liquids

Keywords

  • air content
  • bubble size
  • fibre suspension
  • marcro-instability
  • mixing
  • wet foam

Cite this

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title = "Bubble size and air content of wet fibre foams in axial mixing with macro-instabilities",
abstract = "The air content and bubble size distribution in pure foams and in fibre foams were determined in axial mixing for varied rotation speed, liquid surface tension and wood fibre concentration. Onset of flow macro-instabilities was observed at high rotation speeds both with and without fibres. Before the instability, the bubble size decreased and air content increased with increasing rotation speed. After the instability, the air content was not only strongly affected by rotation speed but, interestingly, both the air content and bubble size increased with reduced surface tension. In both regions, the average bubble size could be explained based on the capillary number after the air content was explicitly included in the model. Added fibres reduced the bubble size in the stable mixing region and for low surface tension levels in the unstable mixing region. This was probably caused by increased shear forces due to inertia of fibres breaking up the large bubbles in the foam.",
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author = "Ahmad Al.Qararah and Tuomo Hjelt and Antti Koponen and Ali Harlin and Jukka Ketoja",
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TY - JOUR

T1 - Bubble size and air content of wet fibre foams in axial mixing with macro-instabilities

AU - Al.Qararah, Ahmad

AU - Hjelt, Tuomo

AU - Koponen, Antti

AU - Harlin, Ali

AU - Ketoja, Jukka

PY - 2013

Y1 - 2013

N2 - The air content and bubble size distribution in pure foams and in fibre foams were determined in axial mixing for varied rotation speed, liquid surface tension and wood fibre concentration. Onset of flow macro-instabilities was observed at high rotation speeds both with and without fibres. Before the instability, the bubble size decreased and air content increased with increasing rotation speed. After the instability, the air content was not only strongly affected by rotation speed but, interestingly, both the air content and bubble size increased with reduced surface tension. In both regions, the average bubble size could be explained based on the capillary number after the air content was explicitly included in the model. Added fibres reduced the bubble size in the stable mixing region and for low surface tension levels in the unstable mixing region. This was probably caused by increased shear forces due to inertia of fibres breaking up the large bubbles in the foam.

AB - The air content and bubble size distribution in pure foams and in fibre foams were determined in axial mixing for varied rotation speed, liquid surface tension and wood fibre concentration. Onset of flow macro-instabilities was observed at high rotation speeds both with and without fibres. Before the instability, the bubble size decreased and air content increased with increasing rotation speed. After the instability, the air content was not only strongly affected by rotation speed but, interestingly, both the air content and bubble size increased with reduced surface tension. In both regions, the average bubble size could be explained based on the capillary number after the air content was explicitly included in the model. Added fibres reduced the bubble size in the stable mixing region and for low surface tension levels in the unstable mixing region. This was probably caused by increased shear forces due to inertia of fibres breaking up the large bubbles in the foam.

KW - air content

KW - bubble size

KW - fibre suspension

KW - marcro-instability

KW - mixing

KW - wet foam

U2 - 10.1016/j.colsurfa.2013.08.051

DO - 10.1016/j.colsurfa.2013.08.051

M3 - Article

VL - 436

SP - 1130

EP - 1139

JO - Colloids and Surfaces A: Physicochemical and Engineering Aspects

JF - Colloids and Surfaces A: Physicochemical and Engineering Aspects

SN - 0927-7757

ER -