Estimation of Flammability Limits of Selected Fluorocarbons with F(sub 2) and CIF(sub3) Page: 57 of 78
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varied from its initial value. The results of these two runs are read by the driver program, and a
new value for the control variable is interpolated or extrapolated from these results. This new
value is used as the starting point for a second iteration, using the better of the previous two runs
as the other starting point. As this process is repeated, the limits should converge to the desired
Twenty repetitions are allowed before the system gives up and goes to the next run in the series.
This limit has proved adequate for the relatively smoothly varying systems treated so far. It is
quite possible, however, for a particular run to have no meaningful solution (e.g., if one is in an
"always non-flammable" region based on concentrations of nonvarying starting materials), and
sometimes an attempt will fail because SOLGAS fails to solve an intermediate case presented to
it in the course of the run. Failed cases do not get reported in the output file but do not halt the
The final reaction temperature supplied to SOLGAS is specified as being the empirical threshold
temperature calculated for the current starting composition. Convergence is defined presently as
"net reaction heat being within 0.02 Id of zero." Typical overall heats of reaction for mixtures
containing about 1 mole of starting material are on the order of 10 to 1000 kJ, so 0.02 allows at
least three significant digit accuracy to the result (much more precise than the accuracy of the
empirical correlation between flammability and adiabatic temperature). This value could be
adjusted within the program but cannot be lowered a great deal without modifying SOLGAS as
well (due to the number of significant digits reported for quantities and temperatures by
To summarize, FLAME4d is set up to
(1) find the "net heat = 0" point.
(2) vary a single starting material's initial quantity.
(3) calculate a threshold ignition temperature from initial composition
(4) write a brief output file containing one line per final run, listing (run #, T, P, names and
starting quantities of materials).
B.2.1 Files Used by FLAME4d
FLAME4d uses several files which are discussed below:
1. FLAME4d.EXE - the program itself.
2. FLAME4d.prm - a text file containing fit parameters for the empirical threshold temperature
used to estimate flammability. These parameter values are separated from the compiled program
to allow easy adjustment should additional experimental data create the need for recalibration or
to allow use with other chemical systems. The best fit of publically available flammability
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Trowbridge, L.D. Estimation of Flammability Limits of Selected Fluorocarbons with F(sub 2) and CIF(sub3), report, September 1, 1999; Tennessee. (https://digital.library.unt.edu/ark:/67531/metadc623234/m1/57/: accessed May 22, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.