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In fire protection engineering, the K-factor formula is used to calculate the volumetric flow rate from a nozzle. Spray nozzles can for example be fire sprinklers or water mist nozzles, hose reel nozzles, water monitors and deluge fire system nozzles.
For law-enforcement-grade pepper spray, values from 500,000 up to 5 million SHU have been reported, [1] [13] but the actual strength of the spray depends on the dilution. [3] This problem can be overcome by stating the water content along with the Scoville value. One way to do so is the "D-value", defined as total mass divided by dry mass. [14]
In a nozzle or other constriction, the discharge coefficient (also known as coefficient of discharge or efflux coefficient) is the ratio of the actual discharge to the ideal discharge, [1] i.e., the ratio of the mass flow rate at the discharge end of the nozzle to that of an ideal nozzle which expands an identical working fluid from the same initial conditions to the same exit pressures.
For example, because flue-gas desulfurization systems must deal with heavy particulate loadings, open, simple designs (such as venturi, spray chamber and moving bed) are used. Also, the liquid-to-gas ratio for the absorption process is higher than for particle removal and gas velocities are kept low to enhance the absorption process.
When a nozzle is used for cleaning, the impact or pressure is called impingement. As with all spray patterns, the unit impact decreases as the distance from the nozzle increases, thereby increasing the impact area size. The spray impact, , depends on the volumetric flowrate Q and pressure drop according to the equation below. The nozzle type ...
As an example calculation using the above equation, assume that the propellant combustion gases are: at an absolute pressure entering the nozzle p = 7.0 MPa and exit the rocket exhaust at an absolute pressure p e = 0.1 MPa; at an absolute temperature of T = 3500 K; with an isentropic expansion factor γ = 1.22 and a molar mass M = 22 kg/kmol.
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The hydraulic calculation procedure is defined in the applicable reference model codes such as that published by the US-based National Fire Protection Association (NFPA), [2] or the EN 12845 standard, Fixed firefighting system – Automatic sprinkler systems – Design, installation and maintenance.