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Unformatted text preview: Abstract: The need for the measurement of flow rates in pipe or channels is common to many industrial processes. It is the objective of this experiment to study some of the more common flow meters used for this purpose, in particular a Pitot tube, a Venturi, and an orifice meters. 5-runs were done for each flow meter. The Pitot tube was used to measure the average velocity. The average error in the velocity was 35.49 % . The error in flow rate measured by the orifice was 21.38 %. The average error in the venturi was 2.48% . However, the values of discharge coefficients were found experimentally to be 1.59 for the orifice with relative error of 156.4% , and to be 1.62 for the venturi with error of 65.3 % . Introduction: Several important types of fluid flow measuring devices are based on the frictionless form of Bernoulli’s equations. In most of chemical process there are gas or liquid flow. Where these need to be at specific limits and hence it’s required measuring its flows continuously. For this purpose there are many flow meters. Each one of them has different properties than others, which make it suitable for specific flow. Some of the common flow meter in industrial processes is the Pitot tube, a venturi tube, a plate orifice, an ISA nozzle, and a bypass flow meter. All the flow meters fond in this experiment use the measurement of a differential pressure as an indirect measure of flow rate. The various flow meters can be connected to an inverted manometer mounted on the rig. Normally the Pitot tube is used to measure the airspeed of airplanes and is often used for measuring the local velocity in pipes or ducts. But the venturi meter and orifice meters are more convenient and more frequently used for measuring flow in enclosed ducts or channels. 1 Theoretical Background: 1.Pitot Tube One of the most common devices for measuring detailed profiles in a flowing stream is the Pitot tube. H. Pitot (1:151) invented this device and its sketch diagram was shown in the laboratory manual. This device consists of two- pressure taps, one connected to the stagnation point at the tip of the tube and a second connected to the static pressure tap. Pitot tube is an instrument for measuring a “ point velocity. The analysis of Pitot tube is done by applying Bernoulli equation to the streamline leading to the stagnation point which lead to an equation of the following form: The pressure P3 is often measured through a tap at the wall since pressure in a cross section normal to the average flow is constant. Furthermore, experimental tests have shown that for a well-designed Pitot tube the friction effect is negligible, so that we read the pressure difference from the meter and calculate the velocity from equ. (1)....
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This note was uploaded on 11/07/2010 for the course CHEMICAL E 300 taught by Professor Ahmedghazal during the Spring '10 term at King Fahd University of Petroleum & Minerals.
- Spring '10