  The physical background behind the success of the Sieder-Tate correction in
heat transfer is analysed. The equivalent correction for mass transfer
correlations is based on the ratio of diffusivities at the wall and bulk
concentrations. This correction is not required if the Prandtl/Schmidt numbers
are evaluated at the wall layer conditions and the Reynolds number at the bulk
conditions. This technique brings heat and mass transfer coefficients into
agreement.
