Diffusion-controlled current distributions near cell entries and corners |
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Authors: | A A Wragg D J Tagg M A Patrick |
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Affiliation: | (1) Department of Chemical Engineering, University of Exeter, Exeter, UK |
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Abstract: | This paper reports experimental work undertaken to explore diffusion-controlled current distributions immediately downstream of sudden changes in flow cross-sectional area such as may occur at the entry to electrochemical flow cells. Nozzle flows expanding into an axisymmetric circular duct and into a square duct have been investigated using the reduction of ferricyanide ions on nickel micro-electrodes as the electrode process. The spanwise distribution of current has also been studied for the case of the square cell where secondary corner flows are significant.Nomenclature
A
electrode area (cm2)
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c
bulk concentration of transferring ions (mol dm–3)
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D
cell diameter (cm)
- D
Diffusion coefficient (cm2s–1)
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F
Faraday number (96 486 C mol–1)
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I
limiting electrolysis current (A)
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k
mass transfer coefficient (cm s–1)
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N
nozzle diameter (cm)
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u
mean fluid velocity (cm s–1)
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x
distance downstream from point of entry to cell (cm)
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z
number of electrons exchanged
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electrolyte viscosity (g s–1 cm–1)
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electrolyte density (g cm–3)
- (Re)D
duct Reynolds number,Du /
- (Re)N
nozzle Reynolds number,Nu /
- (Sc)
Schmidt number, /![rgr](/content/w8x80r7n0703423h/xxlarge961.gif) D)
- (Sh)
Sherwood number,kD/ D) |
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Keywords: | |
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