Vapor Inflow
Use this node to model a vapor inflow originating from an upstream gas mixture in contact with a liquid. The upstream liquid can either be water or a liquid mixture involving any number of components.
vapor inflow
Select an entry from the Upstream liquid system list. The available options are Water, Thermochemistry coupling, and User defined.
Use Water to model incoming water vapor. Saturated vapor, or vapor at a specific relative humidity can be applied.
Thermochemistry coupling can be selected in models that contains a Thermodynamic System coupled to a Chemistry interface. In this case all thermodynamic properties needed (vapor pressure or fugacity, heat of evaporation, liquid phase density) are automatically added to the Thermodynamic system.
Selecting User defined in the Upstream liquid system list, the vapor pressure, Pi, and for each of the species can be manually defined.
For Water and User defined input the Upstream temperature Tustr. For Thermochemistry coupling also input the Upstream absolute pressure Pustr.
Below the settings are detailed for the respective entries of the Upstream liquid system.
When Water is selected, use the Water vapor species list to identify the species solved for that corresponds to water vapor. When needed select to define a Relative humidity.
For Thermochemistry coupling also select an interface from the Chemistry list. In order for a Chemistry interface to be available, it needs fulfill the following criteria:
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The interface should be set to consider a concentrated mixture. This is applied by selecting Concentrated species in the Type list at the top of the Mixture Properties section (in the settings window of the interface).
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The interface should be coupled to a Thermodynamics System. In the Mixture Properties section, select Thermodynamics and chose an appropriate entry from the Thermodynamic system list.
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Gas phase mixture properties should be produced by selecting Gas in the Phase list of the Mixture Properties section.
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The interface cannot have Define variables for porous pellets enabled in the Pellet Chemistry section.
Vapor Species in Equilibrium with Upstream Liquid
When a Thermochemistry coupling is used, select the vapor species which are in equilibrium with the liquid using the check boxes next to the respective species. When a species is correctly coupled, the mass fraction variable as well as the chemical formula and compound name is indicated, for example as “wA, C3H6O (acetone)”. If the species is not correctly coupled, the corresponding label is “wA, Not coupled”. To inspect the coupling, use the Go to source button to navigate to the Chemistry interface. In the Species Matching section make sure that each species is coupled both to a mass fraction solved for as well as to a species From thermodynamics.
Other Species
For the species that are not in equilibrium with the liquid, specify the vapor pressure at the inlet. This could for example be species which are not soluble in the upstream liquid.
Liquid Phase
Use this section to specify the composition in the Upstream liquid system when using a Thermochemistry coupling.
Select a Liquid phase concentration typeMass fraction, Molar fraction, or Volume Fraction. Use the Composition table to specify the corresponding concentration of each species in the liquid.
Transient initialization
When prescribing boundary conditions in time-dependent problems, and in particular vapor pressure conditions, it is important not to introduce a discontinuity with respect to the conditions in the domain. When this happens the solver may struggle to converge and resort to small time steps. When using transient initialization a smooth step function, fs, transitions the boundary condition, from the domain initial value, ω0, to the condition to be applied on the boundary, ωeq, over a small time span Δt. The smoothed value applied on the boundary, ωbnd, is defined as
where
(3-137),
When Duration is set to Automatic the initialization time is automatically defined as a fraction of the time between the initial and the last output
Select User defined to manually define the duration of the transient initialization Δt.