Table of Contents
What is circulate units?
Continuity of flow equation
Common move unit metering methods in open channels
Eyeball methodology
Flow depth (Manning)
Main equipment
Surface Velocity Meters
Transport time meters
Flow unit measurement methods in full tube functions
Venturi meters
Magnetic flowmeter
Turbine flowmeter
Conclusion
What is circulate units?
Flow fee is the quantity of fluid that passes by way of a unit of time. In water sources, move is often measured in cubic ft per second (cfs), cubic meters per second (cms), gallons per minute (gpm), or a wide selection of different items. The measurement of water useful resource circulate is essential for applications corresponding to system management, billing, design and many different purposes. There are several methods to measure move in a water resource system. This article outlines some of the more common strategies of move measurement and offers some helpful information about flow models measurement.
Continuity of circulate equation
For water flowing in a pipe underneath steady-state circumstances (i.e., not varying with time), continuity signifies that water flowing into one end of the pipe should move out of the opposite end. This additionally means that the move in the pipe is identical at any level alongside the length of the pipe. The continuity equation can be expressed as
Flow = Velocity * Area
The idea of continuity in regular state situations ends in the product of velocity * space being equal to a constant at any level in the pipe. This is a useful precept for making move measurements, as shown below.
This is an instance of utilizing the continuity equation to calculate flow. Velocity is measured at 10 ft per second and the cross-sectional space of the flow is measured at 10 square feet. Flow price = 10 feet per second * 10 sq. toes = 100 cubic feet per second.
Common flow unit metering methods in open channels
Eyeball methodology
It is sometimes useful to estimate the circulate velocity and cross-sectional area by eye and then multiply the circulate velocity by the realm to obtain the circulate velocity (continuity equation). A ruler or tape measure can be utilized to improve the accuracy of cross-sectional space measurements, and a stopwatch can be utilized to improve velocity measurements by timing floating particles transferring a set distance. The eyeball technique can be used to estimate move when solely an “order of magnitude” of move is required or when the move fee is merely too low to be measured with a flow meter.
Flow depth (Manning)
When the channel cross-sectional area and channel slope are identified and uniform flow situations exist, the Manning’s equation can be utilized to calculate move by measuring depth only. The Manning’s equation is an empirical equation that describes the relationship between circulate rate in an open channel under uniform circulate conditions and depth, slope and channel friction coefficient (Manning’s n). Uniform flow implies that depth doesn’t vary with the length of the conduit or channel. Flow measurements utilizing Manning’s equation for depth are not relevant to steadily altering circulate circumstances, similar to backwater situations upstream of a dam or weir.
The depth move methodology of flow measurement is more correct than the “eyeball” method. The primary problem with depth-only flow measurements is the potential for inaccurate Manning’s n estimates, cross-sectional areas, and non-uniform move circumstances. This methodology is often used with ultrasonic move meters to estimate the move of a river by measuring only the water degree of the river. Often in these causes, the river level/flow relationship is developed with the assistance of advanced river hydraulic models to account for complicated channel geometry and channel friction conditions.
Main equipment
The main system is used to measure move in open channels, utilizing constructions similar to flumes, weirs or dams, to measure move by measuring depth. The measured depth can then be transformed to a flow fee utilizing an equation or rated curve equation.
Primary gadgets work by forcing the circulate through a path of critical depth, for instance at the top of a weir or on the throat of a flume. In technical terms, the important depth is outlined as the depth of the minimal particular power state that leads to a particular discharge. In follow, this minimum state of vitality means that just one flow corresponds to the critical depth. Therefore, measuring only the depth produces a measurement of the corresponding flux and is subsequently known as a “primary” system.
Primary units are a very handy method of flow measurement because the depth may be measured from above the move without the necessity to insert a sensor within the water. This makes major flow meters extra reliable and simpler to hold up. A disadvantage of primary gadgets is that they can trigger head loss and backwater within the system. Primary gadgets are sometimes considered to be essentially the most correct methodology of measuring open channel move.
Surface Velocity Meters
An space velocity meter is an open channel flow meter that measures circulate by making two separate measurements of depth and velocity. The depth is converted to a cross-sectional area utilizing the geometry of the pipe or channel. The move fee is then calculated by multiplying the flow area by the velocity utilizing the continuity equation, hence the identify “AV meter”. Velocity is usually measured utilizing a Doppler sensor, which displays ultrasound waves back from particles within the fluid and makes use of the Doppler shift within the reflected sound sign to estimate velocity. Some AV meters measure surface velocity optically to estimate velocity.
AV meters are sometimes used to measure open channel circulate in sewers as a end result of the probes are relatively small and they are often put in in existing sewer pipes with out inflicting vital head loss within the pipe. This additionally allows them for use for temporary or short-term circulate metering applications for sewer research. one drawback of AV meters is that the sensor must be put in within the fluid. In sewers, this requires frequent maintenance to wash the sensor. AV meters are often considered less correct than main move meters because major gadgets only need to measure depth and depth measurements are more accurate than velocity measurements.
Transport time meters
Transport time meters had been developed in the oil trade to precisely measure circulate in massive pipelines. They have been used with some success for open channel circulate in water metering functions. Transport time meters also use ultrasound like Doppler meters, however instead of bouncing the sound waves off particles in the water like Doppler move meters, they ship ultrasound waves between two sensors separated from one another by a sure distance along the size of the pipe and makes use of the transmission time of the sound waves to calculate the velocity of the water flow. Because the speed of sound in the water is thought, the velocity of the water may be calculated based on the offset in ultrasonic wave transmission time that occurs as a result of pace of the water.
Transmission time meters can be expensive relative to Doppler move meters due to the many sensors and complicated set up involved. They could be more accurate because of the ability to split the move into horizontal cross sections and measure the rate of every part.
Flow unit measurement strategies in full tube functions
Venturi meters
Venturi flow meters use the Venturi effect to measure flow in a full or pressurized pipe by using the converging part of the pipe to restrict the flow. According to the continuity equation, the cross-sectional area of the converging part is small and due to this fact the speed is greater in the throat. pressure gauge 10 bar to vitality conservation and Bernoulli’s precept, greater velocities within the throat end in a drop in throat strain. The move price can then be determined by measuring the pressure drop in the convergent section and calculating the flow price using Bernoulli’s equation. Venturi meters are more widespread in water metering functions because the strain measurement ports can turn out to be clogged in wastewater purposes.
Magnetic flowmeter
The electromagnetic flow meter works by applying a magnetic subject to the fluid passing by way of the pipe. This causes a small electron potential difference that can be measured by the electrode sensor (due to Faraday’s regulation and electromagnetic induction). The magnitude of the electron potential difference is proportional to the speed of the water, and the continuity equation can then be used to calculate the flow rate.
An advantage of the magnetometer is that the metering section is similar diameter as the adjacent pipe, so the magnetometer causes no additional head loss. For probably the most part, magnetometers are used for full (pressure) pipe applications, however these days open channel magnetometers can also be used.
Turbine flowmeter
A turbine circulate meter is a mechanical move meter that uses a rotating turbine in flow to measure the move of water in a pipe. The speed of the turbine is proportional to the rate and the circulate rate can then be calculated utilizing the continuity equation. Turbine circulate meters are solely used for water functions due to potential problems with wastewater solids collection and clogging generators.
Conclusion
There are many ways to measure flow. Each method has completely different benefits, disadvantages and accuracy in different functions.
เกจวัดแรงดัน is important to understand the characteristics of assorted circulate measurement strategies to help choose the best sort of circulate metering in your software or to properly interpret the move measurements of present flow meters. Tools like Apure (IoT-based water data analysis) help to look at measurements collected by flow meters and perform diagnostics to know move meter efficiency and shortly course of and analyze the information. Contact us for technical or product service assist.
More articles on circulate meters:
Mass flow rate vs volumetric move fee
Relation between move and pressure
Ultrasonic circulate meter working principle
Difference between flow meter and circulate transmitter
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Table of Contents
What is flow units?
Continuity of move equation
Common flow unit metering strategies in open channels
Eyeball methodology
Flow depth (Manning)
Main tools
Surface Velocity Meters
Transport time meters
Flow unit measurement strategies in full tube functions
Venturi meters
Magnetic flowmeter
Turbine flowmeter
Conclusion
What is flow units?
Flow rate is the amount of fluid that passes through a unit of time. In water sources, circulate is commonly measured in cubic feet per second (cfs), cubic meters per second (cms), gallons per minute (gpm), or quite a lot of different units. The measurement of water resource flow is important for applications similar to system control, billing, design and many different purposes. There are several ways to measure move in a water resource system. This article outlines a few of the extra frequent strategies of flow measurement and provides some useful details about circulate models measurement.
Continuity of move equation
For water flowing in a pipe under steady-state conditions (i.e., not varying with time), continuity signifies that water flowing into one end of the pipe must circulate out of the opposite end. This also implies that the move within the pipe is the same at any point alongside the length of the pipe. The continuity equation can be expressed as
Flow = Velocity * Area
The concept of continuity in steady state conditions results in the product of velocity * space being equal to a continuing at any level within the pipe. This is a useful precept for making move measurements, as shown under.
This is an instance of using the continuity equation to calculate flow. Velocity is measured at 10 ft per second and the cross-sectional space of the move is measured at 10 square ft. Flow fee = 10 ft per second * 10 sq. feet = a hundred cubic feet per second.
Common move unit metering methods in open channels
Eyeball methodology
It is usually helpful to estimate the flow velocity and cross-sectional area by eye after which multiply the flow velocity by the realm to acquire the flow velocity (continuity equation). A ruler or tape measure can be utilized to enhance the accuracy of cross-sectional space measurements, and a stopwatch can be utilized to enhance velocity measurements by timing floating debris shifting a set distance. The eyeball technique can be used to estimate move when solely an “order of magnitude” of move is required or when the flow rate is simply too low to be measured with a move meter.
Flow depth (Manning)
When the channel cross-sectional space and channel slope are recognized and uniform move circumstances exist, the Manning’s equation can be used to calculate flow by measuring depth solely. The Manning’s equation is an empirical equation that describes the relationship between flow price in an open channel beneath uniform flow situations and depth, slope and channel friction coefficient (Manning’s n). Uniform circulate signifies that depth doesn’t range with the length of the conduit or channel. Flow measurements using Manning’s equation for depth are not applicable to steadily changing flow conditions, similar to backwater circumstances upstream of a dam or weir.
The depth flow method of move measurement is more accurate than the “eyeball” method. The primary problem with depth-only move measurements is the potential for inaccurate Manning’s n estimates, cross-sectional areas, and non-uniform flow situations. This technique is commonly used with ultrasonic circulate meters to estimate the move of a river by measuring solely the water stage of the river. Often in these causes, the river level/flow relationship is developed with the help of complex river hydraulic models to account for advanced channel geometry and channel friction conditions.
Main gear
The primary gadget is used to measure flow in open channels, utilizing buildings corresponding to flumes, weirs or dams, to measure circulate by measuring depth. pressure gauge measured depth can then be transformed to a circulate rate utilizing an equation or rated curve equation.
Primary units work by forcing the move by way of a path of critical depth, for example on the high of a weir or on the throat of a flume. In technical phrases, the critical depth is outlined as the depth of the minimum specific vitality state that ends in a particular discharge. In follow, this minimal state of vitality implies that just one move corresponds to the critical depth. Therefore, measuring only the depth produces a measurement of the corresponding flux and is therefore called a “primary” system.
Primary units are a really handy methodology of flow measurement because the depth may be measured from above the move without the necessity to insert a sensor within the water. This makes primary flow meters more dependable and easier to take care of. A disadvantage of primary devices is that they can cause head loss and backwater in the system. Primary gadgets are often considered to be probably the most accurate methodology of measuring open channel circulate.
Surface Velocity Meters
An area velocity meter is an open channel circulate meter that measures flow by making two separate measurements of depth and velocity. The depth is transformed to a cross-sectional space using the geometry of the pipe or channel. The flow fee is then calculated by multiplying the move area by the rate using the continuity equation, hence the title “AV meter”. Velocity is usually measured using a Doppler sensor, which displays ultrasound waves again from particles within the fluid and makes use of the Doppler shift in the reflected sound signal to estimate velocity. Some AV meters measure floor velocity optically to estimate velocity.
AV meters are often used to measure open channel move in sewers because the probes are comparatively small and they are often put in in existing sewer pipes with out inflicting important head loss within the pipe. This also allows them to be used for temporary or short-term move metering functions for sewer research. one drawback of AV meters is that the sensor must be installed within the fluid. In sewers, this requires frequent upkeep to clean the sensor. AV meters are often considered much less correct than main circulate meters as a end result of primary devices only have to measure depth and depth measurements are more accurate than velocity measurements.
Transport time meters
Transport time meters have been developed within the oil business to precisely measure circulate in large pipelines. They have been used with some success for open channel move in water metering functions. Transport time meters additionally use ultrasound like Doppler meters, but as an alternative of bouncing the sound waves off particles in the water like Doppler flow meters, they send ultrasound waves between two sensors separated from each other by a sure distance alongside the size of the pipe and makes use of the transmission time of the sound waves to calculate the rate of the water flow. Because the velocity of sound in the water is thought, the speed of the water could be calculated based mostly on the offset in ultrasonic wave transmission time that occurs due to the speed of the water.
Transmission time meters could be expensive relative to Doppler circulate meters as a end result of many sensors and sophisticated set up involved. They could be more accurate due to the capacity to split the flow into horizontal cross sections and measure the velocity of every section.
Flow unit measurement methods in full tube functions
Venturi meters
Venturi circulate meters use the Venturi impact to measure flow in a full or pressurized pipe by using the converging part of the pipe to restrict the move. According to the continuity equation, the cross-sectional space of the converging section is small and subsequently the rate is larger in the throat. Due to power conservation and Bernoulli’s principle, larger velocities in the throat result in a drop in throat stress. The circulate price can then be decided by measuring the pressure drop in the convergent section and calculating the move rate using Bernoulli’s equation. Venturi meters are extra widespread in water metering purposes because the stress measurement ports can become clogged in wastewater applications.
Magnetic flowmeter
The electromagnetic move meter works by applying a magnetic field to the fluid passing by way of the pipe. This causes a small electron potential difference that may be measured by the electrode sensor (due to Faraday’s law and electromagnetic induction). The magnitude of the electron potential difference is proportional to the speed of the water, and the continuity equation can then be used to calculate the move price.
An advantage of the magnetometer is that the metering part is the same diameter as the adjacent pipe, so the magnetometer causes no extra head loss. For the most half, magnetometers are used for full (pressure) pipe applications, but these days open channel magnetometers can additionally be used.
Turbine flowmeter
A turbine move meter is a mechanical circulate meter that makes use of a rotating turbine in move to measure the circulate of water in a pipe. The speed of the turbine is proportional to the speed and the move fee can then be calculated utilizing the continuity equation. Turbine move meters are solely used for water applications due to potential issues with wastewater solids collection and clogging turbines.
Conclusion
There are many ways to measure move. Each technique has completely different advantages, disadvantages and accuracy in numerous functions.
It is important to know the traits of varied circulate measurement strategies to help choose the best type of flow metering for your utility or to correctly interpret the circulate measurements of current flow meters. Tools like Apure (IoT-based water knowledge analysis) assist to look at measurements collected by flow meters and perform diagnostics to know circulate meter performance and rapidly course of and analyze the info. Contact us for technical or product service support.
More articles on circulate meters:
Mass flow price vs volumetric move fee
Relation between circulate and pressure
Ultrasonic circulate meter working principle
Difference between circulate meter and move transmitter