Mist or fog spray nozzles

The full cone or hollow cone pattern produced by many nozzles will break down into a fog/mist after a certain distance from the orifice. If a cone pattern is needed then this breakdown into a true mist is not desirable. But for some applications the breakdown of the spray into a true homogenous fog is the required result. As such, there are a number of nozzles that are designed to specifically produce this effect. A mist pattern is characterised by having a low flow rate of very small droplet sizes with virtually no impact. Typically this pattern will be used for evaporative cooling, moistening or humidifying applications. Fog, mist or spray? Whether a given discharge is classified as a fog, mist or a spray depends up on the mean droplet size. Dry fogs will have Sauter mean droplet sizes of between 10-20 microns Wet fogs will have Sauter mean droplet sizes of between 20 and 30 microns Mists with have Sauter mean droplet sizes of between 30 and 60 microns Anything above 60 microns would be spray A hydraulic nozzle will produce finer and finer droplets as liquid pressure is raised. So a nozzle that produces a mist at 5 bar pressure may well produce a fog spraying at 15 bar pressure. This means the term fog nozzle and misting nozzle are generally interchangeable as the same nozzle may well be able to produce both a mist or a fog depending on the operating pressure.

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