A review on recent technological advancements in multi-ejector concept.

As a consequence of the coming into force of the EU F-Gas Regulation 517/2014, enormous technological developments have been experienced on the part of transcritical R744 supermarket refrigeration systems. These have led to the wide acceptance of multi-ejector based technologies as the most promising hydrofluorocarbon (HFC)-free solutions for commercial refrigeration sector. Approximately 50 stores have been equipped with a multi-ejector block. Furthermore, such an expedient is expected to offer significant electricity savings in other energy-demanding applications (e.g. hotels, gyms) as well, even in warm climates. This work summarizes the evolution of R744 multi-ejector enhanced parallel compression system architectures for supermarket applications. Additionally, their technological aspects as well as the potential energy benefits along with some relevant field/experimental measurements are also presented. Furthermore, the experience gained in the use of the multi-ejector concept in transcritical R744 heat pump technologies is summed up. At last, the persistent challenges needing to be faced are revealed.