Heat transfer and wall effect of flame arrester

Most flame arresters are composed of many small channels or pores of solid material, because this is conducive to the passage of gas, and the requirements for these channels or voids should be as small as possible, small enough to put out the flame. The working principle of flame extinguishing is heat transfer and wall effect.

1. Heat transfer effect

Because the flame arrester is composed of many small channels and gaps, when the flame enters these small channels, many small flame streams will be formed. At this time, the heat transfer area of the channel is very large, and the flame exchanges heat through the channel wall to reduce the temperature, and then the flame is naturally extinguished when it falls to a certain temperature. According to experiments, whenever the thermal conductivity of the flame arrester material is increased to 460 times, the flame extinction diameter is only changed by 216%, which mainly shows that the material is secondary. On the other hand, heat transfer is one of the reasons for extinguishing the flame, but it is not the main reason.

2. Wall effect

Combustion and explosion is not a direct reaction between molecules, but by the excitation of external energy, molecular bonds are destroyed, resulting in activated molecules, activated molecules and split into short life but very active free radicals, free radicals collide with other molecules, generate new products, but also produce new free radicals and continue to react with other molecules. When the combustible gas passes through the narrow channel of the fire blocking element, the collision probability between free radicals and the channel wall increases, and the number of free radicals participating in the reaction decreases. When the channel of the flame arrester is narrow to a certain extent, the collision between the free radicals and the channel wall is dominant, and the reaction cannot continue due to the sharp reduction in the number of free radicals, that is, the combustion reaction cannot continue to propagate through the flame arrester.