- Author
-
Donnelly, M. K.
|
Grosshandler, W. L.
- Title
- Flammability of R-245ca.
- Coporate
- National Institute of Standards and Technology, Gaithersburg, MD
- Journal
-
ASHRAE Transactions,
Vol. 105,
No. 2,
1-8,
1999
- Sponsor
- Air Conditioning and Refrigeration Technology Institute, Arlington, VA
- Contract
- MCLR-PROJECT-660-52401
- Keywords
-
flammability
|
refrigerants
|
test methods
|
thermophysical properties
|
uncertainty
- Identifiers
- counterflow burner
- Abstract
- R-245ca (1,1,2,2,3-pentafluoropropane) has positive thermophysical properties and a zero ozone depleting potential, making it a canadidate to replace some CFC refrigerants. Past measurements using the ASTM E681-85 method suggest that R-245ca is nonflammable at room temperature using dry air, but that increasing the humidity allows for a flame to be momentarily sustained for a narrow range of R-245ca/air mixtures. Establishing the flammability of weak fuels such as R-245ca is difficult in the ASTM E681 apparatus because the dividing line between a propagating and nonpropagating flame can be ambiguous. An alternative means for measuring flammability, using a premixed, counterflow burner, was developed specifically for alternative refrigerants, and has been demonstrated to yield accurate and consistent flammability limits for R-32 and R-125/R-32 mixtures at room temperature and 100 deg C (212 deg F). The same apparatus has been modified to handle the higher boiling point of R-245ca. No steady frames of pure R-245ca in air could be stabilized at the lowest flows attainable in the apparatus; however, when mixed with R-32, flames could be maintained at R-245ca/R-32 ratios up to 62/38. By conducting a series of extinction tests with changing flow rates and mole fractions, the results may be extrapolated to conditions of zero flow (most flammable) and no R-32 to determine if R-245ca and air mixtures are flammable. The results show that R-245ca is flammable at an ambient temperature of 100 deg C (212 deg F) and 50% relative humidity corrected to 23 deg C (73 deg F). When air humidity was kept at 50%, but the initial temperature was reduced to 50 deg C (122 deg F), R-245ca was found to be nonflammable. R-245ca in dry air (0% humidity} at 100 deg C (212 deg F) was also determined to be nonflammable. The measurements confirm the sensitivity of the flammability of R-245ca to initial temperature and humidity.