Nozzles for fire/ explosion prevention systems

Engineering consideration 2 - Getting fine droplets

Breaking any fluid into small droplets takes energy. The finer the droplets required the greater the energy required.   In most nozzles the energy used for atomisation comes from the potential energy of the fluid itself.  This potential energy is essentially a function of flow rate/pressure.  If we ratchet up the fluid pressure more energy becomes available for atomisation but at the same time increased pressure will naturally increase flow rate.

If, as in the case of of fire prevention systems, low flow rates must be maintained then we can see that the product of fine sprays at sufficiently low flow rates might be problematic.  A simple solution is to reduce the spray orifice size.  By forcing fluid through very small orifice at high pressure much of the potential energy is used up breaking apart the liquid in to a fine mist spray pattern.  A potential downside of this approach is clogging of the very small spray orifice. 

Another method of achieving very fine sprays at relatively low flow rates is to impact the fluid on a pin after it exits the orifice.  This impingement method is highly energy efficient meaning that good levels of atomisation can be achieved at even low pressures.