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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.
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.
All gases flow from higher pressure to lower pressure. Choked flow can occur at the change of the cross section in a de Laval nozzle or through an orifice plate. The choked velocity is observed upstream of an orifice or nozzle. The upstream volumetric flow rate is lower than the downstream condition because of the higher upstream density.
An orifice is any opening, mouth, hole or vent, as in a pipe, a plate, or a body Body orifice, any opening in the body of a human or animal; Orifice plate, a restriction used to measure flow or to control pressure or flow, sometimes given specialised names: Calibrated orifice, used to control pressure or flow
A flow limiter or flow restrictor is a device to restrict the flow of a fluid, in general a gas or a liquid. [1] Some designs use single stage or multi-stage orifice plates to handle high and low flow rates. Flow limiters are often used in manufacturing plants as well as households. Safety is usually the main purpose of using a flow limiter.
Venturi tubes are more expensive to construct than simple orifice plates, and both function on the same basic principle. However, for any given differential pressure, orifice plates cause significantly more permanent energy loss. [2]
The coefficient of contraction is defined as the ratio between the area of the jet at the vena contracta and the area of the orifice. C c = Area at vena contracta/Area of orifice. The typical value may be taken as 0.611 for a sharp orifice (concentric with the flow channel). [2] [3] The smaller the value, the greater the effect the vena ...
The Dall tube is a shortened version of a Venturi meter, with a lower pressure drop than an orifice plate. As with these flowmeters the flow rate in a Dall tube is determined by measuring the pressure drop caused by restriction in the conduit. The pressure differential is typically measured using diaphragm pressure transducers with digital readout.