Difluoromethane, also called HFC-32 or R-32, is an organofluorine compound with the formula CH<sub>2</sub>F<sub>2</sub>. It is a colorless gas that is used as a refrigerant. As a hydrofluorocarbon, R-32 is being phased out in the EU.
Synthesis
Difluoromethane is produced by the reaction of dichloromethane and hydrogen fluoride (HF) using SbF<sub>5</sub> as a catalyst.
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Applications
Difluoromethane is used as refrigerant that has prominent heat transfer and pressure drop performance, both in condensation and vaporization.
Difluoromethane is currently used by itself in residential and commercial air-conditioners in Japan, China, and India as a substitute for R-410A. In order to reduce the residual risk associated with its mild flammability, this molecule should be applied in heat transfer equipment with low refrigerant charge such as brazed plate heat exchangers (BPHE), or shell and tube heat exchangers and tube and plate heat exchangers with tube of small diameter.
Many applications confirmed that difluoromethane exhibits heat transfer coefficients higher than those of R-410A
under the same operating conditions but also higher frictional pressure drops. This is lower than the GWP for HFC refrigerants that it is replacing, but remains sufficiently high to spur continued research into using lower-GWP refrigerants.
Difluoromethane is excluded from the 1963 list of VOCs restricted by the United States Clean Air Act due to the ODP being zero.