Environmental Impacts of Halogenated Refrigerants and Their Alternatives: Recent Developments

A certain percentage of the vapor compression based refrigeration, air conditioning and heat pump systems continue to run on halogenated refrigerants due to its excellent thermodynamic and thermo-physical properties along with the low cost. However, the halogenated refrigerants have adverse environmental impacts such as ozone layer depletion potential and global warming. Hence, it is necessary to look for alternative refrigerants to full fill the objectives of the international protocols (Montreal and Kyoto) and to satisfy the growing worldwide demand. In this context, the use of "natural" refrigerants (air, CO2 or ammonia) becomes a possible solution. We introduce in this study the merit of redeploying these natural refrigerants as an alternative solution to replace halogenated refrigerants. This paper reviews the various experimental and theoretical studies carried out around the globe with environment friendly alternatives such as hydrocarbons (HC), hydroflurocarbons (HFC) and their mixtures, which are going to be the promising long-term alternatives. In addition, the technical difficulties of mixed refrigerants and future challenges of the alternatives are also discussed.