The power of water mist

Why is water mist so effective and how does it work? Find here a brief summary of how water mist works for firefighting, ...
#Fire #Dust #Academy #10 years EmiControls

The common denominator for all our solutions is water mist. We took advantage of the fact that tiny droplets dramatically increase the surface area of the used water used.

But why is water mist so effective in a wide variety of applications? And how does it work? We have briefly summarized the modes of action of water mist in firefighting, gas suppression and dust control here.

Firefighting: The advantage of such smaller droplets is that they create a larger water surface and can, therefore, form a larger surface area to absorb heat. The fine mist also has a lower sedimentation speed and can envelop the burning object. It can often even reach into hidden sources of fire that cannot be reached with traditional hoses.
From a physical and thermodynamical point of view, there are several mechanisms, acting simultaneously, by which water mist extinguishes fire. Primarily the water mist efficiently cools the fire plume and the fuel surface, extracting a significant high quantity of heat out of it. This happens thanks to the high latent heat of evaporation (2442J/g) of water. In addition, the water mist displaces and dilutes the oxygen and the fuel vapor in the flame. This happens thanks to the very high expansion rate of water mist (1700 times) when it evaporates to steam. Finally, as a secondary mechanism, water mist also absorbs radiant energy and therefore acts as a thermal barrier, preventing surrounding surfaces (or the fuel itself) from being heated by radiation.

Gas Suppression: Water can naturally absorb gas, but water mist can do it much faster and more efficiently. The finer the water droplets are sprayed, the higher is the water surface created, for the water surface is inversely proportional to the droplet size. The water surface is the interface where the absorption process of gas into water happens. Therefore fine water mist creates a condition where the absorption of gas happens easier and quicker. Once the gas has been absorbed by the water, it can be collected and treated in a controlled way. 

Dust Suppression: The water droplets atomized into fine water mist, combine with the dust particles in the air to make them heavier and bring them down to the ground. The size of the water drops is essential for efficient dust control: the water droplets need to be similar in size to the dust particles to allow them to adhere to them. This means that larger droplets combine with larger dust particles and smaller droplets with smaller particles.

Small Droplets, Big Impact. Since 2011