This section explains the fitcoex utility program. This program is designed for use in conjunction with the towhee_vlcc output files in order to
compute the critical temperature and critical density from a sequence of single-component vapour-liquid simulations. Last updated for version
fitcoex is compiled using the Utility Makefile.
This will create the fitcoex executable which can then be run from the command line.
- cd /towheebase/Utils
- make fitcoex
In order to successfully run fitcoex, two sources of input are required. The first is an input file (*.sim), which contains some comment lines, a value
for the critical exponent "beta", the towhee_vlcc data from at least 3 different temperatures, and a special end of file zero line. The second file
(*.exp) is optional and is for transforming experimental data into a similar format as the simulation data for comparison purposes.
An example with the input files and a for plotting the output is provided in the
File Format for the towhee_vlcc compilation file (*.sim)
File Format for the experimental data file (*.exp)
- Line 1 comment line (typically has a comment about how the data was generated)
- Line 2 comment line (typically says 'beta' to remind the user that the beta value is on the next line
- Line 3 beta (double precision). I typically use a value of 0.325 for this variable
- Line 4 comment line (typically has a header for the vlcc data)
- Line 5 to 5+n towhee_vlcc data lines (double precision).
You must have at least 3 of these lines at different temperatures in order for the code to compute the critical properties.
- Line 6+n zero end line. The code only knows it has hit the end of the file when it gets a line that has a zero value for the variables.
9 double precision zeros go on this line.
There are currently two experimental data file formats implemented into this routine. These files are translated into units of g/ml and output to
several files by fitcoex.
Run the code by typing
- Smith and Srivastava: This format is similar to the one used in the reference book
Smith and Srivastava 1986.
- Line 1 comment line
- Line 2 molecular weight of the molecule (g/mol)
- Line 3 comment line
- Line 4 comment line
- Line 5 to 5+n experimental temperature (K), liquid phase molar volume (ml/mol), and vapor phase molar volume (ml/mol).
- Hensel and Warren: This format is similar to the one used in the reference book
Hensel and Warren 1999.
- Line 1 comment line
- Line 2 molecular weight of the molecules (g/mol)
- Line 3-4 comment lines
- Line 5 to 5+n experimental temperature (C), saturation pressure (bar), liquid density (g/ml), vapor density (g/ml)
Return to the Utility Summary page