CO2 supermarket refrigeration system for hot climates

CO2 single compression cycle is severely penalised when the hot sink temperature approaches the critical temperature; in this situation COP improvement can be obtained with a modified thermodynamic cycle. Parallel compression is a well known method to enhance efficiency and it was already considered as a possible solution for above 0°C supermarket refrigeration purposes. In this paper a theoretical analysis shows how it can actually be a realistic way for commercial refrigeration in hot climates. Technological aspects of multi-compressor systems with independent parallel compressors, as the volume ratio control between main compressors and parallel compressors are faced. The integration with water spray on gas cooler or evaporative cooling can further improve efficiency. Six-month data from a recent installation in Europe are presented, thus demonstrating that this solution is efficient, and it is also mature from a technological point of view so that it can be implemented when necessary.