Flammability limits of binary mixtures of ammonia with HFO-1234yf, HFO-1234ze, HFC-134a, and HFC-125

Flammability limits of binary mixtures of ammonia with HFO-1234yf, HFO-1234ze, HFC-134a, and HFC-125 were measured in dry air. The measurements were made in a 12 L spherical glass flask using ASHRAE method. It has been found that the flammability limits of ammonia and HFO-1234yf mixtures are extremely different from the values predicted by Le Chatelier's equation. Modification of Le Chatelier's equation was made by introducing Ellipse function to analytically express the flammability limits of the mixtures of arbitrary concentrations. HFO-1234ze is non-flammable in dry air, but becomes flammable if ammonia is added more than four percent. If the content of ammonia exceeds 20 percent, the values of flammability limits become very close to the corresponding ones for HFO-1234yf and ammonia. On the other hand, the flammable regions of ammonia mixed with each of HFC-134a and HFC-125 are much narrower than the mixtures of HFO-1234ze. Extension of the ellipse modified Le Chatelier's equation introduced in the above was made to successfully explain the flammability limits of these mixtures. (C) 2013 Elsevier B.V. All rights reserved.