THE REPLACEMENT OF CFCS IN REFRIGERATION EQUIPMENT BY ENVIRONMENTALLYBENIGN ALTERNATIVES

The replacement of chlorofluorocarbons (CFCs) and hydrochlorofluorocar bons (HCFCs) is of prime importance since these refrigerants make up t he vast majority of the working fluids used by the refrigeration indus try and suitable alternatives must be found. A number of suitable pure fluids were considered to establish their properties and, in the case of flammable fluids, a risk analysis was carried out in order to asse ss their safety. The properties of their mixtures were calculated and suitable equations and p-h charts presented. Compressor lubricants hav e had to be changed since the majority of the CFC and HCFC replacement s are hydrofluorocarbons (HFCs). Typically, HFCs are immiscible in the traditional mineral oils and thus a new generation of synthetic oils (usually polyol ester based) have been produced. The properties of the se oils have been investigated and various models, including a modifie d Flory-Huggins equation, have been used to describe their solubility in refrigerants. The effects of refrigerant/oil solubility of the pure refrigerants and their mixtures on system performance have also been analysed and, in the case of refrigerant mixtures, there is a possibil ity of a composition change due to the differential solubility which i nfluences performance. Finally, compact plate heat exchangers were fou nd to be excellent heal exchangers for the refrigeration industry, pro vided that it is remembered that there are control and capacity variat ion limitations associated with their use. The falling film evaporator is studied in derail and there is a possibility that it will fulfill its potential. Compressors tested with alternative refrigerants have s hown (in the case of R407c, a replacement for R22) a deterioration in performance with decreasing evaporator temperature when compared to th at of R22, while some of the flammable refrigerants may require larger compressors than the CFC and HCFC counterparts, due to their smaller mass flow rates. (C) European Communities 1997. Published by Elsevier Science Ltd.