Slotted orifice flowmeter (original) (raw)

Comparison of orifice and slotted plate flowmeters

Flow Measurement and Instrumentation, 1994

The performance of a standard 13 = 0.50 orifice flowmeter is compared to the same flowmeter with a slotted orifice plate replacing the standard orifice plate. The slotted orifice plate has the same total open area as the standard plate and consists of three concentric rings, each of which contains several radial slots. The flow upstream of both orifice plates is preconditioned using a concentric pipe device to produce a wide range of axial velocity profiles without swirl. The discharge coefficient of the standard plate varies from the base value by-1% to +6%, while that of the slotted orifice plate varies by only-0.25%. When swirl is generated upstream of the orifice plates, the discharge coefficients vary by 5% and 2% for the standard and slotted orifice plates, respectively. These data indicate that the slotted orifice flowmeter is superior to the standard orifice flowmeter in maintaining its calibration over a wide range of inlet flow conditions. The slotted orifice plate can be a 'drop in' replacement for a standard orifice plate.

A numerical study of an orifice flowmeter

Flow Measurement and Instrumentation, 2012

An orifice flowmeter used for the measurement of the extensional viscosity has been numerically analyzed by means of the finite volume method. A good agreement with experimental data reported previously in the literature was found. Flow fields, in particular the streamline maps, showed that an excess of pressure is required for removing or minimizing the effect of the flow structures generated downstream the orifice such as vortices and dead zones when using abrupt contractions (8:1). For that reason, a new die geometry based on a semihyperbolic profile was proposed and successfully tested with Newtonian and non-Newtonian fluids resulting in a better performance orifice flowmeter.

Fundamentals of Orifice Meter Measurement Fundamentals of Orifice Meter Measurement

Fluid meters are divided into two functional groups-One measures quantity (Positive Displacement); the other measures rate of flow (Inferential.) All fluid meters, however, consist of two distinct parts, each of which has different functions to perform. The first is the primary element, which is in contact with the fluid, resulting in some form of interaction. This interaction may be that of imparting motion to the primary element; the fluid may be accelerated etc. The second or secondary element translates the interaction between fluid and primary element into a signal that can be converted into volume, weights or rates of flow and indicates or records the results. For example, a weigher uses weighing tanks as its primary element and a counter for recording the number of fillings and dumpings as its secondary element. In an orifice meter, the orifice together with the adjacent part of the pipe and the pressure connections, constitute the primary element, while the secondary element consists of a differential pressure device together with some sort of mechanism for translating a pressure difference into a rate of flow and indicating the result, in some cases also recording it graphically and integrating with respect to the time. This same combination of primary and secondary elements will be observed in almost all other types of meters. Positive Displacement (Quantity Meters)-Some of the more common positive displacement meters are: Weighers, Reciprocating Piston, Rotating Piston, Nutating Disk, Sliding and Rotating Vanes, Gear and Lobed Impeller, and the meter most commonly used to sell small quantities of gas at relatively low flow rates, the Bellows meter. Inferential (Rate Meters)-(a) Orifice Plates-The most commonly used rate or inferential meter is the thin-plate, concentric orifice; a detailed discussion is covered in later paragraphs. (b) Flow Nozzles & Venturi Tubes-Flow Nozzles and Venturi Tubes are primary rate devices which will handle about 60% more flow than an orifice plate for the same bore under the same conditions, and can therefore handle higher velocity flows. If a differential limit is chosen, then a smaller bore nozzle or Venturi may be used to measure the same flow. They are more expensive to install and do not lend themselves to as easy size change or inspection as orifice plates. (c) Pitot Tubes-A Pitot or impact tube makes use of the difference between the static and kinetic pressures at a single point. A similar device which is in effect a multiple pitot tube, averages the flow profile. (d) Turbine Meters-A Turbine meter is one in which the primary element is kept in rotation by the linear velocity of the stream in which it is immersed. The number of revolutions the device makes is proportional to the rate of flow. (e) Swirlmeters, Vortex Shedding Meters, Rotometers, Mass Flow Meters, etc.-These are devices that have applications in flow measurement. The manufacturers should be contacted for detailed information. What is an Orifice Meter? An orifice meter is a conduit and a restriction to create a pressure drop. An hour glass is a form of orifice. A nozzle, venturi or thin sharp edged orifice can be used as the flow restriction. In order to use any of these devices for measurement it is necessary to empirically calibrate them. That is, pass a known volume through the meter and note the reading in order to provide a standard for measuring other quantities. Due to the ease of duplicating and the simple construction, the thin sharp edged orifice has been adopted as a standard and extensive calibration work has been done so that it is widely accepted as a standard means of measuring fluids. Provided the standard mechanics of construction are followed no further calibration is required. An orifice in a pipeline is shown in figure 1 with a manometer for measuring the drop in pressure (differential) as the fluid passes thru the orifice. The minimum cross sectional area of the jet is known as the "vena contracta." How does it work? As the fluid approaches the orifice the pressure increases slightly and then drops suddenly as the orifice is passed. It continues to drop until the "vena contracta" is reached and then gradually increases until at approximately 5 to 8 diameters downstream a maximum pressure point is reached that will be lower than the pressure upstream of the orifice. The decrease in pressure as the fluid passes thru the orifice is a result of the

Beta ratio, swirl and Reynolds number dependence of wall pressure in orifice flowmeters

Flow Measurement and Instrumentation, 1990

Experimental work has been performed in an effort to gain a better understanding of the flow field inside orifice flowmeters and the pressure field generated on the walls of the pipe and orifice plate. As a part of a larger study, extensive wall pressure measurements have been made on the pipe wall from four pipe diameters upstream of the orifice plate to six pipe diameters downstream, as well as on both the upstream and downstream faces of the orifice plate. These measurements were performed for Reynolds numbers of 54 700; 91 I00 and 122800; for beta ratios of O.50 and 0.75 with air as the working fluid. An adjustable swirl plate was installed, which was used to impart varying amounts of swirl into the flow upstream of the orifice plate. For each swirl case, Pitot and static pressure probes were used to characterize the upstream flow field while the pipe wall and orifice plate surface pressures were measured.

Design and Development of Orifice Plate Flowmeter

Accurate and stable gas flows are very important in different applications like, the performance study of vacuum pumps, gauge calibration, leak detection and advance research in low pressure physics. Primary Orifice Plate Flowmeter (OPF) has been designed and developed indigenously. This flowmeter consists of two orifice plates. Orifice-1 (O 1 ) acts as a flow restriction, while orifice-2 (O 2 ) enables continuous pumping mode. By varying upstream pressure 1

Installation effects upon orifice flowmeters

Flow Measurement and Instrumentation, 1992

An experimental study has been undertaken to quantify the effect of the inlet velocity distribution upon the coefficient of discharge, Cd. A two inch (50.8 mm) diameter orifice run was operated at a Reynolds number of 91 000 with a beta ratio, ~, of 0.75. The upstream pipe section was replaced with a one inch pipe mounted concentrically inside the two inch pipe. The mass flowrate was held constant by an array of sonic nozzles upstream of the concentric pipes and was split between the two. By varying the ratio of the flow split, various inlet velocity profiles were generated. The results show that the change in coefficient of discharge is related to first-, second-and third-order moments of momentum: shows the same relationship. This paper proposes the use of this correlation to develop criteria for correcting the discharge coefficient given the variation of the inlet velocity profile from "fully developed' fow. The velocity profile can be measured at the upstream flange tap location with the orifice plate removed, and that profile can be used to generate the moment of momentum to be used to correct the coefficient of discharge.

Response of a slotted orifice flow meter to an air/water mixture

Flow Measurement and Instrumentation, 2001

Flow measurements using differential pressure meters are common in industrial applications. In such cases, the flow of gas is often accompanied by conditions that can lead to liquid condensation. As a consequence, flow measurements basically involve gas-liquid mixture metering. For this reason, errors occur in the metering equipment resulting from the variations in the characteristics of the continuous phase that is present in the flow. In addition, the existence of a dispersed phase leads to the development of flow disturbance and pressure pulsations. Therefore, new methods and tools are being sought to enable the measurements of gas-liquid mixture flows that will offer a suitable accuracy of measurement in the instances of flow interference in the form of a liquid phase. This paper reports the results of a study into the application of orifice plate meters for gas-liquid mixture flow metering. The analysis of the influence of the geometry of an orifice meter on the measurement of a two-phase mixture flow was carried out for this purpose. Experimental tests were carried out by application of a standard orifice and three slotted orifice meters with various designs. The experiments included the measurements of air flow containing small amounts of dispersed water in the form of droplets. The analysis also involved the level of differential pressure that is obtained as a result of applying orifice meters, and the level of the permanent pressure loss caused by the installation of an orifice plate. The results of the research were compared with the results obtained for the standard orifice.

Upstream velocity profile effects on orifice flowmeters

Flow Measurement and Instrumentation, 1994

The effects of upstream velocity profile on the performance of orifice flowmeters were studied. Non-swirling maldistributed axial velocity profiles were obtained using a concentric pipe flow conditioner. Orifice flowmeters with/3 ratios of 0.43, 0.50, 0.60, 0.70 and 0.75 were installed downstream of the flow conditioner and operated at a Reynolds number of 54 700 in a 50.4 cm pipe. Increasing the flow along the centreline of the pipe decreased the pressure drop across the orifice plate, resulting in increased discharge coefficients. The opposite was observed as the flow along the pipe centreline was decreased. The errors increased with increasing/3 ratio. A swirl generator was installed upstream of the/3 = 0.43 and 0.50 orifice plates. The swirl produced effects opposite to the axial velocity. The change in discharge coefficient increased with decreasing /3 ratio.

Characteristics of flow through orifice-meter

JES. Journal of Engineering Sciences/JES. Journal of engineering sciences, 2024

Flow measurements in pipes and open channels are critical for successful water resource management as the economic value of water has increased. Orifice meters are typically used as flow-measuring devices in pipes because they are cheap and simple compared to other devices. Also, orifices are used as energy dissipation methods in water hammer protection devices and hydroelectric power tunnels. Although traditional circular orifice meters have been extensively studied, many points need to be studied. So, experimental and numerical research is carried out to study the effect of orifice geometry on energy loss and the discharge coefficient. The experimental tests are carried out using two different types of orifice plates: circular and triangular, for each one the cross-sectional area is changed four times. The orifice is installed on a 10 cm diameter transparent pipe. The flow rate is changed ten times for each orifice ranging from 13.8 to 49.2 m3/hr. A general correlation equation for the coefficient of discharge is deduced. It was found that the triangular orifice shapes are better than the circular orifice shapes in terms of performance, with reduced head loss and a larger discharge coefficient. By using computational fluid dynamics techniques, the flow behavior through the orifice is analyzed by ANSYS Fluent software. The numerical results confirmed the experimental ones where the pressure head loss for the triangular orifice is lower than the circular orifice and vena contracta is located at a distance equal to half the pipe diameter downstream of the orifice plate.

An improved flow evaluation scheme in orifices of different aspect ratios

Ultrasound in Medicine & Biology, 1997

An accurate and reliable method of regurgitant flow calculation is currently unavailable. The goal of thii study was to define a new general method of flow calculation for orifices of different aspect ratios. The success of the method relies on matching the imaged flow field distribution obtained by color ilow mapping (CFM) to a three-dimensional (3D) numerical Bow field distribution of known geometry. The flow field in three orillces of identical cross-sectional area with aspect ratios of 1 (circular), 2 and 4 (elliptical) was evaluated by: (a) CFM, (b) 3D echocardiographic imaging, and (c) 3D finite element modeling (FEM). The orifice shape and size were accurately estimated by 3D echocardiographic imaging. FEM showed that the normalized centerline velocity profile of the flow field depends on the orilice aspect ratio. CFM provided a good description of the centerline profile for each case. For a given distance from the orifice center, the equivelocity contour surface area increases with increasing aspect ratio. A simple flow calculation scheme was developed to calculate regurgitant flow independent of orifice shape. This improved method showed better results than previous studies and may prove to be advantageous when analyzing in viva flow fields with complex geometries. 0 1997 World Federation for Ultrasound in Medicine & Biology.