![]() The principle of this flow measurement device was first documented by J.B. This is used for the density calculation and the high side input to the differential pressure measurement. The first pressure is measured at the Venturi's upstream location, P 1. With the velocity of the fluid and its density, one can calculate the flowrate.Ī Venturi requires two pressure and one temperature measurement to accurately determine flow. by knowing the pressure and cross-sectional area at two locations, one can calculate the velocity of the fluid. This increase in velocity results in a decrease in pressure which follows Bernoulli's equation. If the area at location A 2 is smaller than A 1, the fluid must travel faster to maintain the same volumetric flowrate. In a closed system mass can be neither created nor destroyed (law of conservation of mass, simply, what goes in, must come out), and as such, the volumetric flowrate at area A 1 must equal the volumetric flowrate at area A 2. The fluid now enters the throat of the Venturi with a new area A 2, which is smaller than A 1. ![]() If potential energy decreases at one location, the kinetic energy must proportionally increase at that location. ![]() Energy is conserved in a closed system, that is, the sum of potential and kinetic energy at one location must equal the sum of the potential and kinetic energy at any another location in the system. These properties form the potential and kinetic energy of the fluid at one location. In the image above, the fluid, either liquid or gaseous, enters the Venturi at the location with a cross-sectional area A 1, pressure P 1, and velocity v 1. Increase in fluid speed results in decrease in internal pressure. After the pressure difference is generated, the fluid is passed through a pressure recovery exit section where up to 80% of the differential pressure generated at the throat is recovered. The Venturi measures a fluid's flowrate by reducing the cross sectional flow area in the flow path and generating a pressure difference. The principle behind the operation of the Venturi flowmeter is the Bernoulli effect. With no moving parts or abrupt flow restrictions, the Venturi can measure fluid flowrates with a minimal total pressure loss. Due to its simplicity and dependability, the Venturi is among the most common flowmeters. The differential producing flowmeter or Venturi has a long history of uses in many applications. The Venturi Principle and Bernoulli's Equation The pressure drop can be measured and correlated with flow rate. Pipe flow measurement is often done with a differential pressure flow meter like the orifice, flow nozzle, and ventruri meter Venturi Meters are discussed in this article.įor each type, a constriction in the flow path causes a pressure drop across the meter. Measurement of the flow rate of a fluid flowing under pressure is carried out for a variety of purposes, such as billing for water supply to homes or businesses, or for monitoring or process control of a wide variety of industrial processes which involve flowing fluids. The other major category of flow is open channel flow, which occurs when there is a free liquid surface open to atmospheric pressure. The closed conduit is often circular, but may also be square or rectangular, such as a heating duct. The term pipe flow rate is often used to refer to flow rate for any closed conduit flow under pressure. Flowmetering allows energy costs to be allocated to a particular product, department or other user this usually resulting in a significant reduction in total energy costs. Where energy is used to provide process or space heating, it is fundamental to know where the costs associated with the energy are actually being incurred. A common example of this would be in steam injection systems for the animal feeds industry.too much steam and the product will not pellet.too little steam and the raw materials will not process and may damage the production machinery. Here the flowmeter is used to measure the rate of fluid or energy flow to allow the process to be controlled and so ensure that the end product is of the required quality. The installation of any flowmeter can be justified in one of two ways. ![]() carbon dioxide, nitrogen, liquors etc.) which are an integral part of the process, or to compressed air, water or steam which are fundamental to plant operation. This applies equally to gases and liquids (e.g. In many of today's industrial processes, it is essential to measure accurately the rate of fluid flow within a system as a whole or in part. ![]()
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