Distribution of mass transport rates along parallel plane electrodes in forced convection

Technical Report · Thu Jan 01 00:00:00 EST 1976

OSTI ID:7356845

Landau, U

Distribution of ionic mass transport rates along a segmented plate-electrode embedded in the wall of a flow channel was measured by the limiting current technique. Local mass transfer coefficients were determined in the electrodeposition of copper with 400 equal to or less than Re equal to or less than 125,000 and Schmidt numbers of 1200 equal to or less than Sc equal to or less than 25,000. In the laminar flow region (400 equal to or less than Re equal to or less than 2500) local transport rates are correlated by Sh/sub x/ = 1.247 (Re Sc(d/sub h/x)/sup 0.331/. In turbulent flow, the length of the entrance section, X/sub e/, is shown to be independent of Sc: X/sub e//d/sub h/ = 756Re/sup -0/./sup 57/. The local turbulent transport rates in the entrance section (0 less than X/d/sub h/ equal to or less than 0.73) are represented by Sh/sub x/ = 0.067Re/sup 0/./sup 75/Sc/sup 1///sup 3/ (d/sub h//x)/sup 0/./sup 3/. Results indicate that the decay of turbulent eddies near a solid wall is proportional to the cube of their distance from it. The exponent on the Re number points towards a St number dependence on ..sqrt..f rather than towards the linear dependence indicated by the Chilton-Colburn analogy. Mechanically grooved electrodes, as well as electrodes with ''random'' type roughness, yield higher limiting rates than on smooth surfaces. The relative height of the roughness elements to the diffusion layer thickness is the dominant parameter. Qualitative information about flow interaction with surface protrusions was gained by inspection of the deposits. Preferential deposition was observed on surface protrusions small with respect to the boundary layer thickness; larger protrusions gave rise to wake-shaped deposits. (DLC)

• Research Organization: California Univ., Berkeley (USA). Lawrence Berkeley Lab.
• DOE Contract Number: W-7405-ENG-48
• OSTI ID: 7356845
• Report Number(s): LBL-2702
• Resource Relation: Other Information: Thesis
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
COPPER
ELECTRODEPOSITION
MASS TRANSFER
CORRELATIONS
DISTRIBUTION
ELECTRIC CURRENTS
ELECTRODES
FLUID FLOW
FORCED CONVECTION
IONS
LAMINAR FLOW
LIMITING VALUES
REYNOLDS NUMBER
ROUGHNESS
TURBULENT FLOW
CHARGED PARTICLES
CONVECTION
CURRENTS
DEPOSITION
ELECTROLYSIS
ELEMENTS
ENERGY TRANSFER
HEAT TRANSFER
LYSIS
METALS
SURFACE COATING
SURFACE PROPERTIES
TRANSITION ELEMENTS
400400* - Electrochemistry