Reactions

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

Domain Selection

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.

Reaction Rates

Add a rate expression R (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 menu. For an example, see the application Fine Chemical Production in a Plate Reactor as linked below.

Reacting Volume

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 the volume of a particular phase.

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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 θ. (θ equals εp for Saturated Porous Media domains).

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For , the expressions are multiplied by the gas volume fraction av = εp − θ. av equals 0 for Saturated Porous Media domains.