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Heat Exchanger Fouling and Cleaning VII
July 1-6, 2007 - Tomar, Portugal
| Editors: |
Hans Müller-Steinhagen, Institute of Technical Thermodynamics, German Aerospace Centre (DLR)
and Institute for Thermodynamics and Thermal Engineering, University of Stuttgart, Germany
M. Reza Malayeri, University of Stuttgart, Germany
A. Paul Watkinson, The University of British Columbia, Canada |
The articles for these proceedings are peer-reviewed.
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MODELLING OF PARTICULATE FOULING ON HEAT EXCHANGER SURFACES: INFLUENCE OF BUBBLES ON IRON OXIDE DEPOSITION.
D.H. Lister, Department of Chemical Engineering, University of New Brunswick, PO Box 4400, Fredericton, NB, Canada, E3B 5A3
F.C. Cussac, Department of Chemical Engineering, University of New Brunswick, PO Box 4400, Fredericton, NB, Canada, E3B 5A3
ABSTRACT:
Studies of iron oxide deposition on Alloy-800 heatexchanger
tubes have been part of a continuing research
program at the University of New Brunswick; the present
work formulates mechanisms for the effect of bubbles on
deposition in water under boiling conditions.
To supplement results from earlier deposition
experiments in a fouling loop at UNB, measurements of
bubble frequency and departure diameter as a function of
heat flux were performed. High-speed movies of bubbling
air/water systems indicated that a pumping action moved
particles from adjacent areas at the surface to bubble
nucleation sites.
To explain the observations, the model considers
deposition and concomitant removal. Deposition includes
microlayer evaporation and filtration through the porous
deposit. The deposit is sparse in the first stage, when the
dominant process is microlayer evaporation including
particle trapping and pumping, creating spots of deposit.
Filtration becomes more important as the deposit thickens to
a stage when microlayer evaporation becomes negligible.
Chimney effects then control. Turbulence due to detaching
and collapsing bubbles affects removal. In sub-cooled
boiling, collapsing bubbles generate enough turbulence to
maintain much of the deposit labile while in bulk boiling
bubble detachment from the nucleation site is dominant and
a smaller portion of the deposit is labile and subject to
removal. Model predictions are presented and shown to
agree quite well with experimental data.
D.H. Lister and F.C. Cussac, "MODELLING OF PARTICULATE FOULING ON HEAT EXCHANGER SURFACES: INFLUENCE OF BUBBLES ON IRON OXIDE DEPOSITION." in "Heat Exchanger Fouling and Cleaning VII", Hans Müller-Steinhagen, Institute of Technical Thermodynamics, German Aerospace Centre (DLR)
and Institute for Thermodynamics and Thermal Engineering, University of Stuttgart, Germany
M. Reza Malayeri, University of Stuttgart, Germany
A. Paul Watkinson, The University of British Columbia, Canada
Eds, ECI
Symposium Series, Volume RP5 (2007). http://services.bepress.com/eci/heatexchanger2007/36
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