Applied methods for assessing flammability risks of HFO refrigerants.

Abstract

This is the 17 slide PowerPoint presentation of Kondziolka, Briggs and Zhang's paper. Manufacturers worldwide are developing substitutes for refrigerants with high global warming potential (GWP) to address climate change concerns. Since 2007, we have used fault tree analysis (FTA) and Computational Fluid Dynamics (CFD) modeling to evaluate the safety of hydrofluoroolefin (HFO) refrigerants in the automotive and stationary sectors, an approach that has proven acceptable to several regulatory bodies. In this paper we describe the overall approach we have used, illustrated by several case examples involving HFO refrigerants (e.g., HFO-1234yf and HFO-1234ze(E)). This includes a description of open source CFD software to assess and visualize refrigerant dispersion. We also discuss the challenges of FTA parameterization when quantitative data are scarce, particularly as regards human factors. Finally, we share our experience using probabilistic tools for evaluating FTA uncertainty and comparative approaches for placing risks in context for the benefit of regulatory authorities.