Equation 1 is the fundamental orifice meter equation. It can be found on page 25 of the 1985 standard and is actually a combination of equations (3) and (7) on that page. Equation 1 describes the theoretical basis, the physical and practical realities of an orifice flow meter. Equation 2, the factored equation, is based on or derived from ...

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.

EQUATIONS FOR FLOW THROUGH ORIFICES The following equations give an approximate flow through orifices and short tubes based on orifice size, pressures and gas involved. They are simple equations that provide only an estimate of flow rate and Aqua Environment Co. Inc. makes no representation or warrenties concerning these equations. An orifice plate is a device used for measuring flow rate, for reducing pressure or for restricting flow. Either a volumetric or mass flow rate may be determined, depending on the calculation associated with the orifice plate. It uses the same principle as a Venturi nozzle, namely Bernoulli's principle which states that there is a relationship between the pressure of the fluid and the velocity of the fluid. When the velocity increases, the pressure decreases and vice versa.

The orifice flowmeter consists of a thin, flat plate sandwiched between flanges or installed in a dedicated fitting. The plate has a precise, sharp-edged orifice, bored concentric with the pipe axis. The flow pattern contracts as it approaches the orifice—the contraction continuing to a distance of approximately one orifice diameter downstream. 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. Orifice plate sizing programs usually allow the user to select the flow equation desired. The orifice plate meter can be made of any material, although stainless steel is the most common. The thickness of the plate used ( 1/8-1/2") is a function of the line size, the process temperature, the pressure, and the differential pressure. Orifice Flow Calculation Data Sheet Calculating an Orifice Diameter It is difficult to accurately calculate the flow of a gas or liquid through a tiny orifice due to the effect of the leading edge of the orifice. In the case of a sharp-edged orifice, the effective diameter is 0.65 times the actual diameter. However, in the case of an orifice