Steady-State and Transient Diffusive Mass Transfer

2 Steady-State and Transient Diffusive Mass Transfer 

The one-dimensional steady-state transport of mass by diffusion is given by Fick s first law [Eq. (3.1.54)], and for a liquid or gaseous slab of constant density with thickness d we obtain  

For a one-dimensional transient diffusion process, we have to use Fick s second law  

Thomas Kilgore Sherwood (1903-1976) an American chemical engineer whose primary research area was mass transfer and its interaction with flow and with chemical reaction. 

Ernst Schmidt (1892-1975) a German scientist in the field of heat and mass transfer who measured the radiation properties of solids and developed the use of aluminum foils as radiation shields. He was the first to measure velocity and temperature fields in free convection boundary layers and discovered the large heat transfer coefficients occurring in condensation. A paper on the analogy between heat and mass transfer caused the dimensionless quantity involved to be called the Sc number. 

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The equations for the steady-state and transient diffusive mass transfer are analogous to those used for heat transfer. Here, we use as mass transfer coefficient and the dimensionless Sherwood number Sh, which is the counterpart to the Nusselt number. 

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