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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.
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.
The proportionality coefficient is the dimensionless "Darcy friction factor" or "flow coefficient". This dimensionless coefficient will be a combination of geometric factors such as π , the Reynolds number and (outside the laminar regime) the relative roughness of the pipe (the ratio of the roughness height to the hydraulic diameter ).
The baseline Coefficient of Discharge values should be within the 95% confidence interval for the RG orifice equation (i.e. the coefficient of discharge equation as provided by AGA-3). Select values of upstream meter tube length, and flow conditioner location, to be used for the performance evaluation.
Churchill equation [24] (1977) is the only equation that can be evaluated for very slow flow (Reynolds number < 1), but the Cheng (2008), [25] and Bellos et al. (2018) [8] equations also return an approximately correct value for friction factor in the laminar flow region (Reynolds number < 2300). All of the others are for transitional and ...
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. Mathematically the flow coefficient C v (or flow-capacity rating of valve) can be expressed as
The orifice plate formula in this article is an adaptation of the formula for a Venturi meter, where a pressure tap does exist in a plane of maximum fluid velocity. The formula below the line "Solving for Q:" in this article is the same as the last formula in this section: Venturi effect#Flow_rate .
A restrictive flow orifice (RFO) is a type of orifice plate.They are used to limit the potential danger, damage, or wastage of an uncontrolled flow from, for example, a compressed gas cylinder [1] [2] They are generally not limiting the flow during normal operation but if a fault or failure occurs causing uncontrolled flow the orifice will present a restriction, limiting the flow.