where d is the dimension of the geometry (for example, 3 for a 3D geometry). If the geometry is very slender, Equation 8-1 tends to give a result that is too large. Then define lref manually.

•Select User defined to define a value or expression for the wall distance Reference length (SI unit: m) in the associated field.

Mass Transfer

Use the Mass Transfer feature to include mass transfer from the dispersed phase to the

continuous phase.

D O M A I N S E L E C T I O N

From the Selection list, choose the domains to include mass transfer defined in this Mass

Transfer feature node.

M A S S T R A N S F E R

Select a Mass transfer model— Two-film theory or User defined. If User defined is selected, enter a value or expression for the Mass transfer from dispersed to continuous phase mdc

(SI unit: kg/(m3·s)).

Two-film Theory

If Two-film theory is selected enter values or expressions for each of the following:

•Mass transfer coefficient k (SI unit: m/s)

•Species concentration in dispersed phase cd (SI unit: mol/m3)

•Species concentration in continuous phase cc. (SI unit: mol/m3)

•Molecular weight of species M (SI unit: kg/mol)

The mass transfer is defined as

mdc = k cd – cc Ma

where k denotes the mass transfer rate, and cd and cc are the species concentrations in the dispersed and the continuous phase, respectively. M equals the species’ molecular weight, and a is the interfacial area between the two phases per unit volume.

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