What: The phase down of high-GWP refrigerants in the mid- and long-terms requires trade-offs between GWP and flammability. Efforts are being made to pursue natural refrigerants such as propane (R290) in residential applications (e.g., mini-split systems) especially in Europe and Asia, but in the U.S. there are still several barriers to be overcome to adopt mildly- and flammable-refrigerants. This lecture provides an overview of the state-of-the-art flammable refrigerant in heat pump applications for residential and commercial buildings, outlines current regulatory limitations and provides an outlook on research activities.
