Power Generation in a Fuel Cell: Reaction Tab

Variable Definitions, Ranges and Default Values

The following table shows a brief description of the variables appearing in this tab. The table also displays their default values and their generally acceptable range:

Variable	Default Value	Range

◙ Molar Coeff. of Reactant The molar stoichiometric coefficient of a reactant.	1.0	Positive
◙ MW of Reactant The molecular weight of a reactant.	MW	Positive
◙ Mass Coeff. of Reactant The mass stoichiometric coefficient of a reactant.	MW	Positive
● Total Mass of Reactants The sum of the mass coefficients of all reactants.	0.0	Positive
◙ Molar Coeff. of Product The molar stoichiometric coefficient of a product.	1.0	Positive
◙ MW of Product The molecular weight of a product.	MW	Positive
◙ Mass Coeff. of Product The mass stoichiometric coefficient of a product.	MW	Positive
● Total Mass of Product The sum of the mass coefficients of all products.	0.0	Positive
○ Reaction Extent (%) The extent of the reaction.	100.0	0-100
○ Ref. Comp. Indicates the pure component that is used as reference for specifying the Reaction Extent (if this is based on a reference component instead of the reaction-limiting component).	<none>	Any Pure Component
● Extent Achieved (of Ref. Comp.) (%) The fractional conversion of the reference component.	0.0	0-100
● Reaction-Limiting Comp. The name of the reaction-limiting component.	<none>	Any Pure Component
● Extent Achieved (of Reaction-Limiting Comp.) (%) The fractional conversion of the reaction-limiting component.	0.0	0-100
○ Enthalpy (kcal/kg) The heat of reaction.	0.0	Negative or Zero
○ Reference Component The pure component that is used as reference for specifying the heat of reaction.	<none>	Any Pure Component
○ Reference Temp. (^oC) The reference temperature of the heat of reaction.	25.0	Positive
○ Electric Efficiency (%) The percentage of the heat of reaction (in absolute terms) that is converted into electricity.	40.0	0-100

Symbol Key: ○ User-specified value (always input); ● Calculated value (always output); ◙ Sometimes input, sometimes output

Specification Choices / Comments

Through this interface you can specify the stoichiometry, progress and heat of an (exothermic) electro-chemical reaction. The following list describes the available specification choices in this tab; for more details on how these are implemented, see Power Generation in a Fuel Cell: Modeling Calculations.

•Register Pure Components

It is possible to introduce new pure components in the process by simply clicking on this button:

This will present you with the Pure Component Registration Dialog that allows you to register new pure components without exiting the stoichiometry balance and the operating conditions dialogs.

•Adding/Deleting Reactants and Products...

Clicking on the button of the Reactants / Products frame displays a list of available reactants / products that can be added to the reaction. Select a component in order to add it as a reactant / product. You can alter the mass/molar stoichiometric coefficient of a reactant/product through the respective table. Note that if a component is used as a reactant it can not be used as a product and vice versa. To delete a reactant or a product, first select it by clicking on the corresponding row number, and then click on the button.

•Stoichiometric Coefficients...

You may choose to specify either mass coefficients or molar coefficients. Use positive coefficients for both products and reactants. Note that the “Molar Coeff.” and “MW” columns are displayed only if the molar option is chosen for the reaction stoichiometry (instead of the mass). The total mass of products and reactants is displayed below each table. The total mass of reactants must be equal to the total mass of products.

•Reaction Extent...

It represents the fractional conversion of the limiting or reference component. Note that if the specified reaction extent based on a reference component is not feasible, the program will use the maximum possible reaction extent (corresponding to extent of 0 or 100%). The extent achieved is displayed in the dialog.

•Reaction Enthalpy...

The reaction enthalpy of an electrochemical reaction must be negative to indicate that this reaction is exothermic (heat releasing).

•Assumed Physical States (PS) of Reaction Participants

Click the ‘PS...’ button to display the “Assumed PS of Participants in Reaction” dialog for the specified reaction. SuperPro offers the option to specify the physical states of the reaction participants (at the specified reference temperature) that correspond to the specified reaction enthalpy. By default, the physical states of the participating components are inferred by the normal boiling point criterion at the reaction reference temperature.