Reactions

Use the node to account for the consumption or production of species through chemical reactions. Define the rate expressions as required.

From the list, choose the domains on which to define rate expression or expressions that govern the source term in the transport equations.

Several reaction nodes can be used to account for different reactions in different parts for the modeling geometry.

Add a rate expression Ri (SI unit: mol/(m3·s)) for species i. Enter a value or expression in the field. Note that if you have the Chemistry interface available, provided with the Chemical Reaction Engineering Module, the reaction rate expressions can be automatically generated and picked up using the drop-down list. For an example, see the application Fine Chemical Production in a Plate Reactor as linked below.

This section is only available when the Mass Transport in Porous Media property is available and selected. See https://www.comsol.com/products/specifications/ for more details on availability.

When specifying reaction rates for a species in porous media, the specified reaction rate may have the basis of the total volume, the pore volume, or in the case of using the volume of a particular phase (applicable when modeling an unsaturated porous medium).

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For , the reaction expressions, in mol/(m3·s), are specified per unit volume of the model domain (multiplied by unity).

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For , the reaction expressions, in mol/(m3·s), are specified per unit volume of total pore space. The reaction expressions will be multiplied by the domain porosity, εp. (εp equals unity for nonporous domains).

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For , the reaction expressions, in mol/(m3·s), are specified per unit volume of liquid in the pore space. The expressions will be multiplied by the liquid volume fraction θl. (θl equals the porosity (εp) on Porous Medium domains).

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For , the reaction expressions, in mol/(m3·s), are multiplied by the gas volume fraction θg = εp − θl. θg equals 0 for Porous Medium domains.