Absorption refrigeration processes with organic working fluid mixtures- a review

The presented work includes a detailed review of organic working fluid mixtures and corresponding Absorption Refrigeration (ABR) cycles available in published literature. Such processes are important as they enable exploitation of cleaner and renewable energy sources for cooling generation. Research efforts may be benefited by a systematically organized account of previous works in organic working fluids, which have received considerably less attention than conventional inorganic options. The reviewed developments are separated into working fluids used in single effect cycles and alternative configurations such as double effect, half effect and so forth. Details are reported regarding the operating conditions tested, the criteria used for working fluid selection and the ones selected as desirable options either experimentally or in simulation studies. Research on thermodynamics of organic working fluids suitable for ABR processes is also reported with respect to measured properties, experimental conditions and types of thermodynamic models. The characteristics of different process flowsheets are also analyzed, while commercial scale ABR applications are reported to motivate research in industrial/commercial scale systems. It is observed that there are few types of chemical groups repeated in working fluid investigations, with halogenated refrigerants and ether- and amide-based absorbents prevailing compared to other substances. Most experimental works pertain to single effect systems, with model-based approaches mainly used due to introduction of increasingly complex process modifications. The latter have been assessed with considerably fewer different fluid options compared to single effect systems. Thermodynamic investigations mainly combine experiments with parameter estimation for model development. Most works derive data and employ the NRTL activity coefficient model, often combined with cubic equations of state.