https://www.relabspray.comRELAB Spray Tech | Applicatons, Industries.enMon, 20 Apr 2026 21:42:19 +0800https://www.relabspray.com/en/technology/flow-rate-and-spray-angle/nozzle-discharge-coefficient-k-factor/https://www.relabspray.com/en/technology/flow-rate-and-spray-angle/nozzle-discharge-coefficient-k-factor/176Nozzle Discharge Coefficient K-factorRELAB<![CDATA[Nozzle discharge coefficient, K-factor]]><![CDATA[Spray nozzles are designed to produce certain spray characteristics, most notable of which is the relationship between fluid flow rate and inlet pressure.]]>https://www.relabspray.com<![CDATA[<p>Spray nozzles are designed to produce certain spray characteristics, most notable of which is the relationship between fluid flow rate and inlet pressure. In attempting to gain some commonality between various manufacturers, styles and capacities, it became readily accepted by the fire protection industry to use the nozzle discharge coefficient (or K-factor) for system design.</p> <p><img src="/files/pic/32556.jpg" alt="k-factor formula" width="368" height="182" /></p> <table width="200" border="0" cellpadding="1" cellspacing="1"> <tbody> <tr> <td>K = Nominal discharge coefficient (K-factor);<br /> Q = Fluid flow rate; <br /> P = Fluid pressure;</td> </tr> </tbody> </table> <p>The &quot;K&quot; discharge coefficient equation is based on a basic derivation involving the Bernoulli and Continuity equations. Though the Bernoulli equation is a functional and robust tool, it has inherent limitations on its use and only yields correct results with all assumptions are met.</p> <p>For the most part, in practice, violations of these assumptions are of little real concern. Unfortunately, many types of real commercial nozzles tend to exhibit unusual flow behavior when closely scrutinized. Though most hydraulic nozzles and nearly all sprinklers follow a normal hydraulic curve, highly engineered sprays, as opposed to standard deflection type sprinklers, often contain complex internal and external geometries used to form the distinctive spray patterns.</p> <p>Most commercial full cone type nozzle designs have an internal vane that imparts radial velocity seen at the orifice exit. As pressure and throughput increase, the nozzle flow rate can be lessened due to internal energy losses and the turbulence induced by the vane, and hence the discharge coefficient appears to be smaller. Complicating matters, friction losses due to turbulent flow are rarely linear in fluid mechanics, and difficult to calculate.</p>]]>