Equilibrate

Equilibrate is a program for the calculation of equilibrium composition. There are different methods for calculating the equilibrium composition of a reacting mixture. For a system that consists of $N$ species and $K$ elements ($N > K$), the elements are conserved, and the classical approach involves the solution of $N+K$ non-linear equations. This approach calculates the moles of different species ($N$ numbers) at equilibrium and $K$ number of Lagrangian multipliers. An alternate method solves $N-K$ non-linear equations involving equilibrium constants and $K$ equations describing component activities. The latter approach is adopted in the equilibrate program.

Running the code

The code is invoked by using the following method.

ReactionEngine.equilibrate — Method

equilibrate(inputfile::AbstractString, libdir::AbstractString)

input_file : Input xml file (String)
lib_dir : The directory where the data files are present. In the present version, the data files are present in the lib directory within the test folder. The user must specify the relative path to the lib directory. The name of the lib directory need not be "lib"

source

On the Julia REPL

julia>using ReactionEngine
julia>equulibrate("equil.xml","../lib/")

Input file

The method takes file_path as the argument. The file_path points to the input XML file. The structure of the XML input file is shown below.

<?xml version="1.0" encoding="ISO-8859-1"?>
<equil>
    <gasphase>CH4 H2 CO CO2 H2O O2 N2 </gasphase>
    <molefractions>CH4=0.6, H2O=0.1, CO2=0.2, N2=0.1</molefractions>
    <T>1073.15</T>
    <p>1e5</p>
</equil>

The meaning of different tags is specified below.

<equil> : The root XML tag for equilibrate
<gasphase> : list of gas-phase species. The species names must be separated by white spaces or tab
<molefractions> : Initial mole fraction of the gas-phase species. Instead of mole fractions, mass fractions may also be specified. In that case, the tag must be <massfractions>. You must ensure that the sum of mass or mole fractions specified is unity. There are no internal checks to ascertain this.
<T>: operating temperature in K
<p>: initial pressure in Pa

Output

The code generates only screen output. An example output is shown below.

Inititial condition:

Species          moles           molefraction
       CH4       6.7244e+00      6.0000e-01 
       CO2       2.2415e+00      2.0000e-01 
       H2O       1.1207e+00      1.0000e-01 
        N2       1.1207e+00      1.0000e-01 
        CO       0.0000e+00      0.0000e+00 
        O2       0.0000e+00      0.0000e+00 
        H2       0.0000e+00      0.0000e+00 

Equilibrium composition @ T= 1073.15 K and p=100000.0 Pa

Species          moles           molefraction
       CH4       3.3912e+00      1.8973e-01
       CO2       1.2649e-02      7.0766e-04
       H2O       1.6324e-02      9.1329e-04
        CO       5.5621e+00      3.1118e-01
        O2       3.2984e-23      1.8454e-24
        H2       7.7709e+00      4.3476e-01
        N2       1.1207e+00      6.2703e-02