Estimation of Flammability Limits of Selected Fluorocarbons with F(sub 2) and CIF(sub3) Page: 25 of 78
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which has units of pressure and includes both the local shock pressure and the momentum term
due to local movement of gas.
The pressures and temperatures calculated from this model are presented in the summary section
of the spreadsheets under the heading "Detonation Model." The "Shock" entries give the T and
P values (in various units) within the shock wave. The "Impulse" pressure includes both the
shock pressure and the (directed) equivalent pressure due to gas movement.
184.108.40.206 Flame Limits
The 1992 prediction of flammability was based on a correlation between composition and
adiabatic temperature. The reconstituted (1999) detonation theory spreadsheets do not contain
the identical calculation of adiabatic temperature as the original models (a constant volume,
isentropic, temperature is calculated rather than the constant pressure adiabatic temperature as in
the original); the final temperature is calculated in an analytically more accurate manner;
thermodynamic parameters are in some cases different). Because of these differences, a revised
calibration is needed. Keeping the spirit (and functional form) of the original technique, but
using the isentropic temperatures calculated in the new model series, an equation bounding
experimental data at flammability boundaries for several fuel-oxidizer systems similar or
identical to those of interest yields the following formula: "a mixture is predicted to be
flammable if its isentropic temperature after reaction exceeds the larger of 800K or
[250K In (X dXf)+ 1251K ]. Details of the calibration of this equation are contained in
220.127.116.11 Model Implementation
The 1999 version of the explosion theory model is implemented in spreadsheet form. The model
was developed in Quattro Pro 8 format (part of Corel's WordPerfect Office Suite 8), but was also
converted to Lotus 1-2-3 (version 5) and Microsoft Excel 97. Six versions of the model were
developed, one for each combination of two oxidizers (F2 or ClF3) with three fuels (coolants
CFC-114, c-C4F8, or C4F0). Each spreadsheet is suitable only for reactions involving its specific
pair of reactants. Normal user inputs are initial temperature, pressure, volume, and starting gas
composition. Results are calculated automatically when input values change. Key output values
are collected in a summary table, consisting of temperatures and pressures at several conditions
(e.g., at the final adiabatic condition and at shock conditions). Details of operation of the models
are contained in Appendix A.
The fundamental chemical assumption in the model is that the reaction of fuel and oxidizer can
be approximated by specified chemical reactions that are assumed to go to completion to the
extent permitted by the available quantities of reactants. For each fuel/oxidizer combination, a
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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/m1/25/: accessed May 23, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.