Refrigeration systems for hot climates using CO2 as the working fluid

The purpose of this paper is to illustrate the perspectives of carbon dioxide as a refrigerant in hot climates and to show state-of-the-art solutions that can promote the use of CO 2 transcritical cycles in those regions where the ambient conditions are challenging for this technology. Staged throttling and compression are well known methods to increase energy efficiency: when carbon dioxide is used in extremely warm climates, their adoption can help in keeping the efficiency at an acceptable level, as well as in overcoming technological issues, like the compressor discharge temperature. Evaporative cooling is investigated in details as a general way to improve efficiency in vapour compression cycles. An estimation of water consumption will be presented both for dry and humid hot climates. Some water consumption measurements, collected in a recent installation in Australia, are presented.