Orifice meter presents a cheaper method to measure the rate of flow through the pipe. The expanding section of venturi meter returns the flow. For orifice meter cross sectional area to orifice meter s2 1. What is the difference between venturimeter and orificemeter. Fm 308 flow measurement by venturi and orifice meter. The water flow rate can be adjusted using the valves on the hydraulics bench. The venturi meter has a converging conical inlet, a cylindrical throat and a diverging recovery cone. For a venturi meter, the discharge coefficient is typically. Laboratory experiment on venturi meter and orifice meter. Bengtson orifice and venturi pipe flow meters for liquid.
I have this misconception about pressure drop of venturi meter and orifice meter. Energy losses through venturi, orifice, and rotameter flowmeters. The following figure shows the venturi meter with uniform cylindrical section before converging entrance, a throat and divergent outlet. The venturi meter is a piping component and should be handled with th e same safety precautions. Each has built in excel formulas to calculate unknowns like the pipe flow. The inlet section is a standard asme longradius nozzle with a throat diameter dv of 0. The orifice meter, the nozzle meter, and the venturi meter are the most common devices used to measure the instantaneous flowrate. As the name implies, it consists of an orifice plate which is the basic. The eccentric or more costly segmental orifice is used for more difficult fluids. If a pump forces the liquid through a tube connected to a system consisting of a venturi to increase the liquid speed the diameter decreases, a short piece of tube with a small hole in it, and last a venturi that decreases speed so the pipe gets wider again, the gas will be sucked in through the small hole because of changes in pressure. The reading of manometer h m is employed to get h, as discussed before. If wear was not a problem the orifice remained the meter of choice. Orifice flow meter s are ideal for measuring air and gas flows in combustion systems. Venturi meter is a device or component which is used for measuring the rate of flow of liquid through pipes.
One of the disadvantages of orifice meters is the large irreversible pressure loss across the orifice, which results in substantial pumping costs in case of large diameter pipes. Venturi meter presents a costlier method to measure the rate flow of fluid through the pipe. The throat length of these meters is equal to the throat diameter. Comprehensive teaching package as optional attachments. Use excel formulas for orifice, venturi meter and ideal. Both are used to measure the flow rate of gases and liquids. Use the tables on page 4 and 5 for sizing a flanged, carbon steel orifice. In general a orifice plates has turndown ratio between 3. This also work on the same principle as that of venturimeter. Most modern browsers have builtin pdf readers if you have problems opening this file in your browser, check your browsers or computer systems settings. Gaskets are provided to seal both sides of the plate. Fm 308 flow measurement by venturi and orifice meter objectives.
Install meter in the pipe line so that the flow directional arrow agrees with the direction of the. By employing the continuity equation and bernoullis principle, the volumetric flow rate through the orifice meter can be calculated as described previously for venturi meter. When the venturi meter is inclined, the potential head changes. The inlet diameter equals d 26 mm and the throat diameter d 16 mm. Screwed brass venturi vbs use the tables on pages 2 and 3 for sizing a threaded orifice. Orifice meter the venturi meter described earlier is a reliable flowmeasuring device.
Venturi meters are costly and used only when absolutely necessary. The concentric orifice plate flow meter reduces the pressure by forcing the fluid through a thin plated circular opening. It works on the basic principle of bernoullis equation. Select the orifice by either pressure drop or by flow. This is considered by many users to be the standard or classical venturi meter. Flow measurement in pipes and ducts ced engineering. Venturi tube has a smooth entry as well as a smooth exit. Each of these meters operates on the similar principle. The expansibility factor is applied to the flow equation in the same way as the discharge coefficient.
The proper method of installing a halmi venturi meter 2 caution. In simple language, this is defined as the sum of pressure energy, kinetic energy per unit volume and potential energy per unit volume equal in the same. To find the coefficient of discharge for orifice meter. Venturi meter vs orifice meter student cheresources. To define the quantity of gas measured, the base pressure must be defined. A schematic of the venturi meter is shown on the diagram at the end of the procedure. This pressure is set by contract, by governmental law or as an agreement of the measurement by the two parties. I have read about pressure recovery for both meters and found that there is always a permanent pressurehead loss dependent on the area ratio for orifice while for venturi, fluid slows down in a cone with smaller angle where kinetic energy is converted back to.
Excel templates can be downloaded to make venturi meter and orifice flow meter calculations in u. Energy losses through venturi, orifice, and rotameter. Determine that the meter is installed with the arrow on the nameplate and on the meter body pointing in the direction of the flow. For these reasons it is widely used, particularly for large volume liquid and gas flows. A small drain or vent hole is drilled in a standard orifice to vent gas or drain liquid. Pdf experimental investigation of the installation. However this meter is relatively complex to construct and hence expensive. Inserttype venturi flow meter installation and operation. It uses the same principle as a venturi nozzle, namely bernoullis principle which states that there is a. Due to the smooth transition to the throat and gradual transition back to full pipe diameter, the head loss through a venturi meter is quite low and the discharge coefficient is quite high. Various forms of construction of a venturi meter are employed, depending on size, but all are. Meters should have at least 10 pipe diameters of smooth, clean, straight pipe upstream and downstream for accurate readings. Unlike the orifice meter, the fluid jet after passing through the restriction throat of venturi expands to a large area gradually. A venturi can also be used to mix a liquid with a gas.
Tr 12 kgs 3 kgs 4 normally expressed as turndown ratio of 4. It has no projections into the fluid, no sharp corners and no sudden changes in contour. To find the coefficient of discharge for venturi meter. The proper method of installing a venturi meter 2 caution. This is a typical turndown ratio for a orifice plate. Venturi meter and orifice meter are the commonly used flow meters for measuring massvolumetric flow rate or velocity of the flowing fluid. An orifice meter is a conduit and a restriction to create a pressure drop. The pressure at the entrance to the meter is gauge and it is undesirable that the pressure should at any point, fall below absolute.
Discharge coefficient performance of venturi, standard. As we learned in the impact jet lab, the speed of a moving jet of water is proportional to the waters velocity. This is evident in a turbine flow meter, where the impact force of the water on the blades sets the rotor in motion. The pressure along the meter is obtained using the 11 pressure taps at the locations shown on the diagram. As the flow area in a pipe decreases, the flow velocity that is accompanied by a decrease in pressure. Venturi flow meter installation and operation manual. Schematic diagram of orifice plate the orifice flow meter consists of a 20mm bore tube with an orifice of 12mm. Venturi meter flow is measured using the differential pressure principle differential pressure integrated with time, so that it is used to any engineering parameters like flow rate. A venturi tube is a device which consists of a convergent inlet connected to a cylindrical throat which is in turn connected to a conical expanding section called the divergent exit. However, the same principle can be exploited with only minimal pressure loss with the use of a venturi meter. Calibration of an orifice plate flowmeter mechanical engineering department king saud university riyadh submitted by. It uses the same principle as a venturi nozzle, namely bernoullis principle which states that there is a relationship between the pressure of the fluid and the velocity of the fluid. Flow meter performance, validation and compliance to 40.
The venturi flow meter obtains a pressure differential by constricting the flow area and therefore increasing the velocity at the constriction, which creates a lower pressure according to bernoullis theorem. To determine the coefficient of discharge of the orifice meter 1. Unit operations of chemical engineering by mccabe and smith. Venturi meterconstruction, working, equation, application. Energy losses are less in a venturi meter whereas energy losses.
Venturi meter a cross section of the brass venturi meter tested is shown in figure 3. The principle of the method of measurement is based on the installation of a venturi tube into a pipeline in which a fluid is running full. The turndown ratio tr for an orifice meter with maximum flow of 12 kgs and a minimum flow of 3 kgs can be calculated as. This article contains three example excel templates that can be downloaded. Venturi meter and orifice meter are the commonly used flow meters for measuring massvolumetric flow rate or velocity of the flowing fluid an orifice plate is a device used for measuring flow rate. It consists of flat circular plate which has a circular hole, in concentric with the pipe. Flow measurement with orifice,venturi and rotameter engi. An orifice meter is basically a type of flow meter used to measure the rate of flow of liquid or gas, especially steam, using the differential pressure measurement principle. It is mainly used for robust applications as it is known for its durability and is very economical. The ratio of the orifice plate bore divided by the inside pipe diameter. There are many different meters used to measure fluid flow.
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