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Orifice plate showing vena contracta. An orifice plate is a thin plate with a hole in it, which is usually placed in a pipe. When a fluid (whether liquid or gaseous) passes through the orifice, its pressure builds up slightly upstream of the orifice [1] but as the fluid is forced to converge to pass through the hole, the velocity increases and the fluid pressure decreases.
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.
The most common method of measuring gas flow is via differential pressure across an orifice plate inserted into a flow metering pipe. As the differential pressure is not directly proportional to the gas flow rate, a flow computer algorithm is required to convert the differential pressure reading into a flow rate (may include square root ...
Orifice plate includes derivation of non-choked gas flow equation. de Laval nozzles are venturi tubes that produce supersonic gas velocities as the tube and the gas are first constricted and then the tube and gas are expanded beyond the choke plane. Rocket engine nozzles discusses how to calculate the exit velocity from nozzles used in rocket ...
An orifice plate is a plate with a hole through it, placed perpendicular to the flow; it constricts the flow, and measuring the pressure differential across the constriction gives the flow rate. It is basically a crude form of Venturi meter, but with higher energy losses. There are three type of orifice: concentric, eccentric, and segmental. [7 ...
A simplified version of the definition is: The k v factor of a valve indicates "The water flow in m 3 /h, at a pressure drop across the valve of 1 kgf/cm 2 when the valve is completely open. The complete definition also says that the flow medium must have a density of 1000 kg/m 3 and a kinematic viscosity of 10 −6 m 2 /s , e.g. water.
An orifice gas meter consists of a straight length of pipe inside which a precisely known orifice plate creates a pressure drop, thereby affecting flow. Orifice meters are a type of differential meter, all of which infer the rate of gas flow by measuring the pressure difference across a deliberately designed and installed flow disturbance.
An orifice plate meter has a practical turndown ratio of 3:1. A turbine meter has a turndown ratio of 10:1. Rotary positive displacement meters have a turndown ratio of between 10:1 and 80:1, depending on the manufacturer and the application. Diaphragm meters are considered to have a turndown ratio of 80:1.