According to such a phase-out program, two main strategies are outlined. The former deals with the development of new equipment working with natural refrigerants, hydrocarbons
(HCs) and new generation low GWP fluids (Calm, 2008).
The latter deals with the retrofitting of the existing plants switching their working refrigerant to a lower GWP fluid. According to such a latter strategy, the recent literature studies the replacement of ozone depleting CFC-12 and HCFC-22 to HFCs, HCs and HFC/HC mixtures. Further experimental studies are focused on the retrofitting of HFCs with lower GWP HFCs, HCs and hydrofluoroolefins/hydrofluoroolefin-based mixtures. A review of such retrofitting operations is in Table 2.
Some of these contributions show that an optimized retrofitting of the existing refrigeration systems may improve their efficiency and reduce the environmental impact without significant investments in the system re-design. Finally, about the technological innovations and use of renewable energy in the refrigeration, several scientific contributions analyze the performances of different fluids within heat pump and heat pipe (Esen, 2004; Esen and Esen, 2005; Palm, 2008).