The impact of droplets

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How does water flow and pressure affect the extinguishing capacity?

To efficiently absorb heat, droplet size and spray pattern are essential. The surface of the water droplet absorbs and cools the heat radiation from the fire gases.

Many small droplets create a larger effective spray area per litre of water. Therefore, getting as large an effective surface area as possible is vital.

Depending on pressure and flow, the droplet size from a spray nozzle varies. For example, a conventional system has low pressure and a high water flow, which generates a good throw length but larger droplets than a system with high pressure and low water flow.

Cobra uses a pressure of 300 bar and a flow rate of 60 l/min, which results in many small droplets in a fine water mist, giving a large effective surface area. With its long throw length, Cobra can quickly cool the fire gases and reduce the temperature in the fire compartment.

A metaphorical explanation

A metaphorical explanation

The metaphor of a football pitch can be used to describe this fact in a more understandable and tangible way. In this example, the same amount of water is used in all illustrations.

Why droplet size and spray pattern matters
A given volume of water introduced at 8 bar will cover half a football goal.

Why droplet size and spray pattern matters
The same amount of water introduced at 40 bar will cover half the penalty field.

Why droplet size and spray pattern matters
The same given amount of water introduced by a Cobra at 260 bar will cover the whole football pitch field.

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