In
fire protection engineering
Fire protection engineering is the application of science and engineering principles to protect people, property, and their environments from the harmful and destructive effects of fire and smoke. It encompasses engineering which focuses on fi ...
, the K-factor formula is used to calculate the
volumetric flow rate
In physics and engineering, in particular fluid dynamics, the volumetric flow rate (also known as volume flow rate, or volume velocity) is the volume of fluid which passes per unit time; usually it is represented by the symbol (sometimes ). I ...
rate from a
nozzle
A nozzle is a device designed to control the direction or characteristics of a fluid flow (specially to increase velocity) as it exits (or enters) an enclosed chamber or pipe.
A nozzle is often a pipe or tube of varying cross sectional area, ...
. Spray nozzles can for example be
fire sprinkler
A fire sprinkler or sprinkler head is the component of a fire sprinkler system that discharges water when the effects of a fire have been detected, such as when a predetermined temperature has been exceeded. Fire sprinklers are extensively used ...
s or
water mist nozzles, hose reel nozzles, water monitors and deluge fire system nozzles.
Calculation
K-factors are usually calculated in
metric unit
The metric system is a system of measurement that succeeded the decimalised system based on the metre that had been introduced in France in the 1790s. The historical development of these systems culminated in the definition of the Internat ...
s internationally.
Metric units
Using metric units, the volumetric flow rate of a nozzle is given by
, where ''q'' is the flow rate in
litre
The litre (international spelling) or liter (American English spelling) (SI symbols L and l, other symbol used: ℓ) is a metric unit of volume. It is equal to 1 cubic decimetre (dm3), 1000 cubic centimetres (cm3) or 0.001 cubic metre (m3 ...
s per minute ( l/min ), ''p'' is the
pressure
Pressure (symbol: ''p'' or ''P'') is the force applied perpendicular to the surface of an object per unit area over which that force is distributed. Gauge pressure (also spelled ''gage'' pressure)The preferred spelling varies by country a ...
at the nozzle in
bar
Bar or BAR may refer to:
Food and drink
* Bar (establishment), selling alcoholic beverages
* Candy bar
* Chocolate bar
Science and technology
* Bar (river morphology), a deposit of sediment
* Bar (tropical cyclone), a layer of cloud
* Bar (un ...
and ''K'' is the ''K-factor'' is given in units of
.
US customary units
K-Factors have also previously been calculated and published using the
United States customary units
United States customary units form a system of Units of measurement, measurement units commonly used in the United States and Territories of the United States, U.S. territories since being standardized and adopted in 1832. The United States cust ...
of
pound per square inch
The pound per square inch or, more accurately, pound-force per square inch (symbol: lbf/in2; abbreviation: psi) is a unit of pressure or of stress based on avoirdupois units. It is the pressure resulting from a force of one pound-force applied to ...
(psi) and
gallon
The gallon is a unit of volume in imperial units and United States customary units. Three different versions are in current use:
*the imperial gallon (imp gal), defined as , which is or was used in the United Kingdom, Ireland, Canada, Aus ...
per minute (gpm). Within the United States, US measurements are still often used instead of metric.
Unit confusion
Care should be exercised not to intermix K-factors from metric and Imperial/US units, as the resulting factors are not equivalent or interchangeable.
Sprinkler manufacturer who lists both types of K-factors
/ref> In case of mix-ups, results can be catastrophal.
References
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Fire protection