Difluoromethane, properties

Sato, A., Nakajima, T. (1979) A structure-activity relationship of some chlorinated hydrocarbons. Arch. Environ. Health 34, 69-75. Sato, T., Sato, H., Watababe, K. (1994) PVT Property measurements for difluoromethane. J. Chem. Eng. Data 39, 851-854. Scharlin, P, Battino, R. (1995) Solubility ofCCl2F2, CC1F3, CF4, andCH4 in water and seawater at 288.15-303.15 K and 101.325 kPa. 

The development of CFC alternatives has focused on non-chlorinated compounds, such as hydrofluorocarbons (HFCs), which have similar physical properties, but break down in the lower atmosphere.110 111 Consequently, hydrodechlorination is a simple method for the production of HFCs and also for destruction of CFCs108,109,112-114. Palladium is unique among the catalytic metals for its activity and selectivity in this process,102-108,115,116 but using Pd-Au/SiC>2 (Pd Au = 60 40) increased the selectivity for difluoromethane from difluorodichloromethane (CFC-12) shown by Pd/Si02 at 453 K from 40 to 95%.109,112-114... 

The values in these tables were generated from the NIST REFPROP software (Lemmon, E. W, McLinden, M. O., and Huber, M. L., NIST Standard Reference Database 23 Reference Fluid Thermodynamic and Transport Properties—REFPROP, National Institute of Standards and Technology, Standard Reference Data Program, Gaithersburg, Md., 2002, Version 7.1). The primary source for the thermodynamic properties is Tillner-Roth, R., and Yokozeki, A., An International Standard Equation of State for Difluoromethane (R-32) for Temperatures from the Triple Point at 136.34 K to 435 K and Pressures up to 70 MPa, J. Fhys. Chem. Ref. Data 26(6) 1273-1328,1997. Validated equations for the viscosity are not currently available for this fluid. The source for thermal conductivity is unpublished however, the fit uses the functional form found in Marsh, K., Perkins, R., and Ramires, M. L. V, Measurement and Correlation of the Thermal Conductivity of Propane from 86 to 600 K at Pressures to 70 MPa, /, Chem. Eng. Data 47(4) 932-940, 2002. 

The material in the preceding section is generally relevant to Halon 1211 bromochloro-difluoromethane (CBrClFj) systems as far as effectiveness is concerned. There are some minor differences. Instead of being odorless, it has a faintly sweet smell, but otherwise many of the physical properties are similar. Given in Table 3.9 are the extinguishing characteristics for Halon 1211. Again, the two materials are very similar, as can be seen by a comparison of the data in Table 3.9 to the corresponding information in Table 3.8 for Halon 1301. 

To illustrate the development of a transport property correlation, discussion is focused here on the relevant example of binary mixmres of two new alternative refrigerants. A global correlation, based on theory where possible, is desired for the transport properties of mixtures of difluoromethane (R32) and pentafluoroethane (R125). This activity represents a portion of a project currently under way at National Instimte of Standards and Technology (NIST). Viscosity data for R125 have been published (Diller Peterson 1993), and the thermal conductivity data surface for R125 is shown in Figure 7.1. Primary data will be available for kinematic viscosity, thermal conductivity and thermal diffusivity from 180 to 400 K in the vapor, liquid and supercritical phases as well as... 

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