Use this node to model a reaction where the kinetics is so fast that the equilibrium condition is fulfilled at all times. The node solves for an additional degree of freedom (the reaction rate Req) to fulfill the equilibrium condition at all times in all space coordinates.

If the Apply equilibrium condition on inflow boundaries check box is selected, the specified inflow concentration values in all active Inflow boundary nodes for the physics interface are modified to comply with the equilibrium condition.

The list defaults to Equilibrium constant or select User defined. For either option, the Apply equilibrium condition on inflow boundaries check box is selected by default.

For Equilibrium constant, enter an Equilibrium constant Keq (dimensionless). Also enter a value or expression for the Unit activity concentration Ca0 (SI unit: mol/m3). Selecting Equilibrium constant defines an equilibrium condition based on the stoichiometric coefficients, the species activities, and the law of mass action.

For User defined, enter an Equilibrium expression Eeq (dimensionless).

Enter a value for the stoichiometric coefficientνc (dimensionless). The default is 0. Use negative values for reactants and positive values for products in the modeled reaction.

Species with a stoichiometric coefficient value of 0 are not affected by the Equilibrium Reaction node.