State of the art on the flammability of hydrofluoroolefin (HFO) refrigerants.

Hydrofluoroolefins (HFOs) have been attracting increasing attention over the recent decade, and some of them are regarded as candidates for next-generation refrigerants. In this paper, the flammability characteristics of forty-eight HFOs and blends have been relatively comprehensively and systematically summarized, for a variety of experimental conditions on the basis of the results reported in academic journal papers, professional books, conference proceedings, technical reports, patent applications, material safety data sheets, and presentations. The following flammability characteristics of HFOs are reviewed, including the lower flammability limit, upper flammability limit, burning velocity, minimum ignition energy, hot surface ignition temperature, autoignition temperature, thermal decomposition temperature, heat of combustion, product of combustion, etc. Besides, a new correlation equation has been suggested to roughly indicate the burning velocity and heat of combustion rankings of the fluorinated hydrocarbons once their basic molecular characteristics are known. In addition, the experimental methods, influencing factors, inerting mechanism, and developing tendency of the flammability of the HFO refrigerants are discussed. The details presented are expected to be useful for researchers working in the field of heating, ventilation, and air conditioning and refrigeration. [ABSTRACT FROM AUTHOR]