# Flow coefficient

Flow coefficient

The flow coefficient of a device is a relative measure of its efficiency at allowing fluid flow. It describes the relationship between the pressure drop across an orifice, valve or other assembly and the corresponding flow rate.

Coefficent of discharge is ratio between the actual flow rate to Theoretical discharge.

In mathematical terms, the "flow coefficient" Cv is the volume (in US gallons) of water at 60°F that will flow per minute through a valve with a pressure drop of 1 psi across the valve.

Numerically this definition can be expressed as:

$C_v = F sqrt\left\{dfrac\left\{SG\right\}\left\{Delta P$

The use of the flow coefficient offers a standard method of comparing valve capacities and sizing valves for specific applications that is widely accepted by industry. The general definition of the flow coefficient can be expanded into equations modeling the flow of liquids, gases and steam as follows:

For gas flow, in a pneumatic system, the CV for the same assembly can be used with a more complex equation. [ Swagelok CV Flow Coefficient [http://www.swagelok.com/downloads/webcatalogs/EN/MS-06-84.PDF "Swagelok CV Flow Coefficient", ] Absolute pressures (psia) must be used for gas rather than simply differential pressure.

For air flow at room temperature, when the outlet pressure is less than 1/2 the absolute inlet pressure, the flow becomes quite simple (although it reaches sonic velocity internally). With CV = 1.0 and 200 psia inlet pressure the flow is 100 standard cubic feet per minute (scfm). The flow is proportional to the absolute inlet pressure so that the flow in scfm would equal the CV flow coefficient if the inlet pressure were reduced to 2 psia and the outlet were connected to a vacuum with less than 1 psi absolute pressure (1.0 scfm when CV = 1.0, 2 psia input).

=Definitions=Cv = Flow coefficient or flow capacity rating of valve.

F = Rate of flow (US gallons per minute).

SG = Specific gravity of fluid (Water = 1).

ΔP = Pressure drop across valve (psi).

References

Wikimedia Foundation. 2010.

### Look at other dictionaries:

• linkage flow coefficient — srauto sieties faktorius statusas T sritis radioelektronika atitikmenys: angl. linkage flow coefficient; linkage flux factor vok. Hopkinsonscher Streufaktor, m; verketteter Flußfaktor, m rus. коэффициент потокосцепления, m pranc. coefficient d… …   Radioelektronikos terminų žodynas

• coefficient d'Hopkinson — srauto sieties faktorius statusas T sritis radioelektronika atitikmenys: angl. linkage flow coefficient; linkage flux factor vok. Hopkinsonscher Streufaktor, m; verketteter Flußfaktor, m rus. коэффициент потокосцепления, m pranc. coefficient d… …   Radioelektronikos terminų žodynas

• Flow measurement — is the quantification of bulk fluid movement. Flow can be measured in a variety of ways. Positive displacement flow meters acumulate a fixed volume of fluid and then count the number of times the volume is filled to measure flow. Other flow… …   Wikipedia

• Coefficient De Traînée — Un mobile se déplaçant dans un fluide pesant subit de la part de ce fluide une distribution de pression dont la résultante s oppose à sa marche. La composante de cette résultante selon la direction du mobile est appelée traînée. L intensité de la …   Wikipédia en Français

• Coefficient de trainee — Coefficient de traînée Un mobile se déplaçant dans un fluide pesant subit de la part de ce fluide une distribution de pression dont la résultante s oppose à sa marche. La composante de cette résultante selon la direction du mobile est appelée… …   Wikipédia en Français

• Flow stress — is defined as the instantaneous value of stress required to continue deforming the material to keep the metal flowing. It is the Yield Strength of the metal as a function of strain, which can be expressed: [1] Yf = Ke^nYf = Flow stress, MPaK =… …   Wikipedia

• Coefficient — For other uses of this word, see coefficient (disambiguation). In mathematics, a coefficient is a multiplicative factor in some term of an expression (or of a series); it is usually a number, but in any case does not involve any variables of the… …   Wikipedia

• Coefficient de traînée — Un mobile se déplaçant dans un fluide pesant subit de la part de ce fluide une distribution de pression dont la résultante s oppose à sa marche. La composante de cette résultante selon la direction du mobile est appelée traînée. L intensité de la …   Wikipédia en Français

• Coefficient of performance — The coefficient of performance or COP (sometimes CP), of a heat pump is the ratio of the change in heat at the output (the heat reservoir of interest) to the supplied work. Contents 1 Equation 2 Derivation 3 Improving COP 4 …   Wikipedia

• coefficient of viscosity — noun a measure of the resistance to flow of a fluid under an applied force • Syn: ↑absolute viscosity, ↑dynamic viscosity • Hypernyms: ↑coefficient …   Useful english dictionary