Abstract
In 1987 AKZO applied for patents regarding the application of mixtures of dimethylether (DME) and dichlorodifluoromethane (CFC 12) as refrigerants. Mixture ratios range, according to the patent application, between 12 and 35% DME (% by weight). Special emphasis is currently given to the non-flammable mixture of 13% DME and 87% CFC 12. This particular azeotropic refrigerant mixture is proposed by AKZO as a temporary substitute for CFC 12, pending the introduction of suitable alternative refrigerants. It is an attractive temporary substitute, because it can replace CFC 12 in many applications without major retooling and without deterioration of refrigerating performance. Because of its reduced CFC 12 content, substitution of CFC 12 with an azeotropic mixture of CFC 12 and DME gives an immediate reduction of CFC 12 emissions and thus reduces the potential for stratospheric ozone depletion. The present Paper gives an overview of the development programme after its initiation in 1984. The programme addresses the following areas: Refrigerating performance. Experiments comparing CFC 12 and the azeotropic mixture of CFC 12 and DME in domestic, automobile and industrial refrigerating units. Theoretical analysis. Thermodynamics. Theoretical prediction of thermodynamic properties. Experimental determination of azeotropic behaviour. Flammability. Experiments for ranges of mixture ratios. Toxicity. Chemical decomposition studies. Toxicity testing. Endurance and reliability. Oil compatibility. Corrosion and wear testing in domestic refrigerators. Compatibility with synthetic materials. Effusion tests. The progress in these areas is described and further planned activities are discussed.
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