Estimation of Flammability Limits of Selected Fluorocarbons with F(sub 2) and CIF(sub3) Page: 15 of 78
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work begun in 1992. The original commission of this work was to document the bases and
operation of the two 1992 models. After some investigation, it became obvious that it would be
necessary to update and revise the models at least to a degree to allow operation with current
computer operating systems and supporting software. Thus, the task expanded to include the
revision of the original models. If the methods are to be usable over several years, past
experience indicates that the underlying bases need to be documented so that the methods are not
purely dependent on any particular software or computer architecture.
This report briefly discusses the 1992 versions of the models and the development of the 1999
versions (including theory, algorithms, and reference experimental data), presents selected results
of operating the models, and finally documents operation of the current versions of the models.
2. MODEL DEVELOPMENT
2.1 EXPLOSION THEORY MODELS
2.1.1 1992 Explosion Theory Models
In 1991 and 1992, E. J. Barber developed a computer model designed to estimate the maximum
pressure that could be generated on combustion or explosion of a flammable gas mixture. The
fuel/oxidizer combinations consisted of pairs taken from the oxidizers F2 and CIF3 and the
"fuels" CFC-114, c-C4F8 and n-C4F0. This model was also used to empirically predict the
composition limits of flammability of gas mixtures such as outlined in report K/ETO-111.
Examination of Dr. Barber's archives indicates that this model actually consisted of a number of
spreadsheets, each devoted to a specific narrow range of conditions: (1) the specific combination
of fuel/oxidizer and, (2), within a given fuel oxidizer pair, a limited range of fuel-to-oxidizer
ratios. In principle, a complete set of spreadsheets would cover all ratios of all 6 combinations of
coolant/fluorinating agent. Only one fuel/oxidizer combination, however, 'was completely
covered by the available versions and 4 other combinations were partially covered in the 22
separate spreadsheets present in the Barber computer archives.
An outline of the general method used in each of these spreadsheet versions of the model is as
1. Postulate one or more characteristic reactions involved in the combustion, and assume they go
2. From the starting materials, calculate the quantities of final products.
3. Compute the energy release in the reaction.
4. Apply flame theory to predict the final pressure inside a fixed volume of gas after it burns
adiabatically (i.e., without energy gain or loss).
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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/m1/15/: accessed May 27, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.