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Alph Reaction Example

Note - this example requires optional compounds that can be purchased in the Alph Store.

From your device, you can download the completed example


This case performs a simple conversion reaction to model the combustion of methane with air. The flame temperature of the product is determined. It makes use of the reaction model from the Model Library case.

Main Diagram

There are four fluids in main Information Flow Diagram of this case:

A simple mixture of 21% oxygen and 79% nitrogen at approximately room conditions. The flow is an arbitrary 400 kgmole/h.

A pure methane fluid, again at approximately room conditions. The flow has been set to 30 kgmole/h, to allow for adequate excess oxygen for combustion.

The mixture of the air and fuel fluids as calculated by the Mixer tool.

This fluid represents the products of an adiabatic reaction as calculated by the burner model tool., so its temperature will be the adiabatic flame temperature.

The Reaction Model

The IFD for the reaction model tool named burner looks like:

Please be sure and check the notes for this tool as well as for it input and output objects.

Reaction Tool Fluids

This fluid represents the products of an isothermal reaction. As such the temperature and pressure are set to equal that of the feed. The composition is set to the variable p, where the reaction product compound flows will be calculated. See the p variable in the next section. The fluid flow is simply the sum of these compound flows.

{ sum $p }

This fluid represents the products of an adiabatic reaction, so its temperature will be the adiabatic flame temperature. The pressure, flow and composition are all set to be the same as the iso fluid, but the enthalpy is calculated by the formula:

( @iso.q + $q ) / @iso.f

which simply takes the iso energy flow and adds to it the heat of reaction calculated in the variable q and then divides the sum by the flow rate.

Reaction Tool Variables

The main calculations for this problem are done in the following variables:


This array holds the stoichiometric coefficients for the reaction:

CH4 + 2O2 => CO2 + 2H2O + Q

Thus the values are -1 and 1 for methane and carbon dioxide respectively and -2 and 2 for oxygen and water respectively. Nitrogen is inert and so is given a value of 0.


This variable holds the quoted name of the compound upon which the reaction extent is to based. In this case "methane".


This variable is assigned the fraction of the basis compound consumed in the reaction. For this example we have used 0.95.


This array holds the reactant flows and is calculated by the simple product of the feed mole fractions and molar flow:

#feed * #feed.f


This variable contains the extent of the reaction in terms of the amount of methane consumed. This is the flow of the basis compound in the feed times the extent, divided by the negative of the stoichiometric factor for the basis compound:

#feed.x:$basis * #feed.f * $extent / (-$s:$basis)

Note that no checks are done to ensure there are sufficient other reactants.


This array holds the compound flows of the reaction product. It is calculated by the surprisingly simple formula:

$r + $s * $e

For each compound, its flow in the product fluid will just be the reactant flow plus its stoichiometric coefficient times the extent of the reaction in terms of methane.


This is where the energy produced by the reaction is calculated. VMGThermo enthalpies do not include heats of formation, so a correction has to be applied in the form of the rxnbasis property. The formula is:

(#feed.h + #feed.rxnbasis) * #feed.f
(@iso.h + @iso.rxnbasis) * @iso.f

By adding the rxnbasis property to the fluid enthalpy and multiplying the result by the fluid flow, we get values that can be subtracted to calculate the energy produced.