Refrigerant Transitions...Again PDF

This paper reviews the progression of refrigerants from inception of mechanical refrigeration to the present. It divides historical and current refrigerants into separate generations and discusses the selection criteria distinguishing them. The four generations include slightly overlapping periods based on whatever worked (1830s-1930s), improved safety and durability (1931-1990s), stratospheric ozone protection (1990s-2010s), and attention to global warming (2012-?). The paper discusses the primary refrigerants employed in each period and goes on to examine the viability of the imminent fourth generation, responding to limits and anticipated limits to acceptable refrigerant global warming potential (GWP). The paper presents factors challenging or likely to challenge the fourth generation refrigerants. Among the potential driving factors are efficiency, momentum, prices, litigation and liability, unforeseen suitability issues, local impacts, and political naivete. The paper summarizes impacts from these concerns, individually or in combination, and their potential to necessitate a subsequent fifth generation. Notwithstanding the controversial and uncertain nature of predictions, the paper suggests an approach to selecting future refrigerants in the absence of ideal choices and of new chemical families that might better approach them. Despite what many practitioners now consider the second transition during their careers, retiring still new but now familiar candidates (or a third transition including the earlier advent of fluorochemicals), the paper concludes that industry must choose between forward-looking selections, which go beyond minimum mandates, or face refrigerant transitions...again.