This paper describes the latest findings of a project to identify azeotropic and near azeotropic mixtures with a normal boiling point of between -40°C and -80°C. The aim was to match the saturated pressure-temperature characteristics and refrigerating capacity of existing refrigerants within this range (such as R410A and R744), whilst achieving higher critical temperatures and - where relevant - lower triple point temperatures. Thus, the intended outcome is an extended range of applicability and an improvement in energy efficiency. Of a large number of potential combinations, three azeotropic and near azeotropic mixtures have been selected, all formed from natural refrigerants or synthetic chemicals with a global warming potential (GWP) of less than 150. These mixtures were subject to a variety of analyses, including thermodynamic, performance and safety assessments. Patents have been filed and published and global licensees are now being sought.
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