Effect of temperature and humidity on the flammability limits of hydrocarbons

In this study, the flammability limits of R290 and R600a were measured in different environmental conditions. All the experiments were performed on a self-made experimental rig at temperature ranging from 5 to 55 degrees C and relative humidity of air ranging from 0 to 100%. The results showed that the temperature dependences for the flammability limits of both R290 and R600a can be predicted by linear model precisely. The humidity dependences for the flammability limits of R290 and R600a were distinctive, which was increased slowly for lower flammability limits (LFLs) but changeable for the upper flammability limits (UFLs). Meanwhile, it was found that the flammability limits of both R290 and R600a became sensitive with the relative humidity changing. A special case for the water vapor influencing on the flammability limits of hydrocarbons was found, especially for UFLs. It has maximum and minimum values in the experimental curve of UFLs when the relative humidity increased from 0 to 100%, which revealed that water vapor does not inhibit the combustion of hydrocarbons simply.