Flammability Measurements of Difluoromethane in Air at 100 Deg C.
Flammability Measurements of Difluoromethane in Air at
100 Deg C.
Grosshandler, W. L.; Donnelly, M. K.; Womeldorf, C. A.
ASME/JSME Joint Thermal Engineering Conference, 5th
Proceedings. American Society of Mechanical Engineers
(ASME)/Japan Society of Mechanical Engineers (JSME).
March 15-19, 1999, San Diego, CA, 1-8 pp, 1999.
Sponsor:Air-Conditioning and Refrigeration Technology Institute,
flammability measurements; difluoromethane; refrigerants
Difluoromethane (CH2F2, or R-32) is a candidate to
repIace currently used ozone-depleting
chlorofluorocarbon refrigerants. Because CH2F2 is
flammable, it is necessary to assess the hazard posed by
a leak in a refrigeration machine. The currently
accepted method for determining flammability, ASTM E
681, has difficulty discerning the flammability boundary
for weak fuels such as CH2F2. This paper describes an
alternative approach to identify the limits of
flammability, using a twin, premixed counter-flow flame.
By using the extinction of an already established
flame, the point dividing flammable from non-flammable
becomes unambiguous. The limiting extinction mixture
changes with stretch rate, so it is convenient to report
the flammability limit as the value extrapolated to a
zero stretch condition. In the burner, contoured
nozzles with outlet diameters of 12 mm are aligned
counter to each other and spaced 12 mm apart. The lean
flammability limit of CH2F2 in dry air at room
temperature was previously reported by the authors to be
a mole fraction of 0.14, using the twin counter-flow
flame method. In the current study, relative humidity
was not found to affect the lean limit. Increasing the
temperature of the premixed fuel and air to 100 deg C is
shown to extend the flammability limit in the lean
direction to 0.13. The rich Iimit of CH2F2 found using
the counter-flow method is around 0.27. The
uncertainties of the measurements are presented and the
results compared to data in the literature.