Correlations for mass transfer are often arranged into equations where all terms occur as dimensionless groups. One advantage of doing this is that any set of units can be used as long as the group remains dimensionless. A second advantage is that if the form of the correlation is not suggested by theory, dimensional analysis can be used to determine appropriate forms for the dimensionless groups.
Mass-transfer correlations are often reported as the Sherwood number Sh, which is defined as
The Sherwood number is the ratio of the actual rate of mass transfer to the mass transfer due to diffusion alone. The appropriate ...