R-245ca (1,1,2,2,3-pentafluoropropane) has positive thermophysical properties and a zero ozone depleting potential, making it a candidate 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 °C (212 °F). The same apparatus has been modified to handle the higher boiling point of R-245ca. No steady flames 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 °C (212 °F) and 50% relative humidity corrected to 23 °C (73 °F). When air humidity was kept at 50%, but the initial temperature was reduced to 50 °C (122 °F), R-245ca was found to be nonflammable. R-245ca in dry air (0% humidity) at 100 °C (212 °F) was also determined to be nonflammable. The measurements confirm the sensitivity of the flammability of R-245ca to initial temperature and humidity.

Units: Dual