Peclet number for the wall-tube electrode

The mass transport equation is:


where (under a 1st order convection approximation):


and the hydrodynamic constant, a is given by1:


Defining the dimensionless lengths:

R = r/re and Z = z/re(A5.5)

and substituting for R and Z, gives the dimensionless form of the mass transport equation:


Similarly the velocity expressions become:


Substituting for vr and vz gives:


Where Ps is the (shear rate) Peclet number:



a = a(R,Z,Ps)(A5.11)

However the dimensionless current:


is calculated from the flux at the electrode surface, where Z = 0. Furthermore R is integrated out, thus the dimensionless current is a sole function of the Peclet number. Note that this result is only valid for a 1st order convection approximation.


1 W.J. Albery, S. Bruckenstein, J. Electroanal. Chem., 144, (1983), 105.