Figure 4.9 Effects of v and Φ on the
accuracy of the proposed method for
the calculation of the internal mass
transfer effectiveness factor for a
spherical catalyst and a 1st order
kinetics.
(39)
where ηext and ηint are the effectiveness factors when only external and internal diffusion
resistances occur respectively.
Another way to calculate ηT is to use equation (21). However, the boundary condition
(25) is no longer valid since the substrate concentration at the surface of the support is
different from the bulk substrate concentration due to the external diffusional resistances.
Under steady state conditions, the flux of substrate through the support surface per unit of
support surface area equals that through the outer diffusion layer. Thus, the correct
boundary condition is expressed as:
(40)
By using dimensionless variables, this equation yields:
Multiphase bioreactor design 110