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69) 7 I 9 7 5 . 984-986 e VCH Verlagsgesellrchaft mbH, D-69469 Weinheim, 1997 0009-286X/970707-0984 517.50+.50/0 ' electrodes 0 -[5] HINDERER, 1.; KEIL, F.J. on the occasion of his 65th birthday L1 ventilation fan ProblemIt is a now well-established fact that chlorofluorohydrocarbons, once emitted to the atmosphere, can lead to ozone depletion in the stratosphere due to their long atmospheric life times. When looking for new candidates for replacing the chlorofluorohydrocarbons (CFC) as refrigerants partly fluorinated hydrocarbons (HFC) and mixtures of these have been proposed. These substances are said not to participate in ozone degradation andhydrogen being only partly substitutedshow reduced atmospheric life time. Components with higher hydrogen content, however, tend to be combustible at atmospheric conditions. To prevent this to occur, mixtures made up of HFC have come to life as promising candidates. In some earlier papers, flammability limits and minimum ignition energies have been reported for pure and mixed HFC [l-41. All these mixtures, however, imply only partly fluorinated candidates. Therefore, it would be interesting to investigate the flammabilitybehavior of a fully fluorinated compound (FC) mixed with a nonhalogenated compound and compare it to the above-mentioned. In some recent papers, mixtures including a FC have been discussed as a possible candidate for refrigeration application [5,6]. In this paper, we report about measured flammability limits for blends (octafluoropropane + propane, R 218 + R 290) and (octafluoropropane + methane, R 218 + R 50) in mixture with air. ExperimentalFor measuring the flammability limits of (octafluoropropane + propane) and (octafluoropropane + methane), an existing experimental setup has been applied. It consists of one refrigerants cylindrical vessel (V = 4.5 1) which allows to measure flammability limits and minimum ignition energy according to DIN 51649 [7]. The principle layout is shown in Fig. 1.A small window at the head of the vessel allows to observe the ignition process. The vessel and all piping is made of stainless steel. The mixtures of (octafluoropropane + propane) and (octafluoropropane + methane) with air were prepared at a total pressure of 1 bar according to their partial pressures assuming the ideal gas law to be valid and isothermal mixing conditions at 298 K. Ignition energy of an electrical spark (the gap length between the electrodes being 5 mm) can be varied in a continuous manner between 0.5 mJ and 150 J. The latter value was used for the measured flammability limits. A homogeneous fuel gadair mixture was established by running a small ventilation fan prior to the experiments. The explosion experiments were initiated by central spark discharge. ResultsBy heating a flammable mixture to elevated temperatures reaction is started which may proceed with sufficient speed to ignite the mixture. The means of supplying the required energy to heat up a local volume may be by hot surfaces, electrical sparks or an open flame. In order to ignite the m...

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Literatur [1] Kohlen, R.; Becker, C. D.; Ruppert, K. A,: Chem.-1ng.-Tech. 64 (1992) Nr. 4. S. 3761377 durch Extrapolation MS2034192. 30 Schnelle, deflagrative, laminare und t u rbu len te C HJLufi-Fla m menf ron t-Ausbreitung in geschlossenen spharischen Explosionsbehaltern Dip].-Ing. B. Leisenheher (Vortragender)