Initial Values
Use this subnode to specify the initial values used by the solver of the dependent variables defined by the parent node.
In the Initial Values subnode to the H2 Gas Phase and O2 Gas Phase nodes, Mixture specification in the Initial Composition section can be used to specify mixture composition in Mole fractions or Humidified mixture for all gas phase domains. The O2 Gas Phase node has an additional option of Humidified air for O2 gas phase domains.
The option Mole fractions is always available and text fields are used to specify the mixture composition for all included species.
Humidified mixture allows for specifying a gas mixture using values for a dry gas mixture, which is subsequently humidified to a specified relative humidity. The setting is available if H2O has been selected in the corresponding Gas Mixture section on the interface top node, and text fields are used to specify the mixture composition for all included species except H2O. Additionally, the Relative humidity, Humidification temperature, and Humidification absolute pressure of the humidifier are also specified.
Humidified air is available if H2O and N2 have been selected in the O2 Gas Mixture section on the interface top node. Relative humidity, Humidification temperature, and Humidification absolute pressure of the humidifier are also specified. The dry mole fractions of the included species are set internally as follows: 0.79 (N2), 4e-4 (CO2) and 1e-6(CO).
Given that the humidifier (inlet) temperature (Thum), absolute pressure (pA,hum) and relative humidity (RHhum) of the humidifier (inlet) gases are known, the conversion from a set of dry (containing no water vapor) molar fraction to a corresponding humidified mixture may be calculated as follows. The water mole fraction is defined as
The wet mole fractions for all species except water are then calculated from the dry mixture molar fractions according to
In the Initial Values subnode to the Membrane node, Specify water chemical potential as can be used to specify water Activity, Liquid water pressure, or water Chemical potential. The default From parent option specifies water activity for Vapor equilibrated model and liquid water pressure for Liquid equilibrated model, respectively, chosen on the parent node.