Useful information about circulate items

Table of Contents

What is circulate units?

Continuity of circulate equation

Common flow unit metering methods in open channels

Eyeball technique

Flow depth (Manning)

Main equipment

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 volume of fluid that passes through a unit of time. In water resources, flow is often measured in cubic feet per second (cfs), cubic meters per second (cms), gallons per minute (gpm), or quite lots of different items. The measurement of water resource circulate is essential for functions such as system management, billing, design and a lot of other applications. There are a number of methods to measure circulate in a water useful resource system. This article outlines a few of the more common strategies of move measurement and supplies some helpful information about flow units measurement.
Continuity of circulate equation

For water flowing in a pipe underneath steady-state situations (i.e., not varying with time), continuity signifies that water flowing into one finish of the pipe should flow out of the other end. This additionally implies that the flow in the pipe is the same at any level along the length of the pipe. The continuity equation can be expressed as

Flow = Velocity * Area

The idea of continuity in steady state conditions results in the product of velocity * area being equal to a constant at any point in the pipe. This is a helpful precept for making move measurements, as shown under.
This is an instance of using the continuity equation to calculate move. Velocity is measured at 10 toes per second and the cross-sectional area of the circulate is measured at 10 square toes. Flow fee = 10 feet per second * 10 square toes = a hundred cubic toes per second.
Common move unit metering strategies in open channels

Eyeball methodology

It is typically useful to estimate the move velocity and cross-sectional area by eye and then multiply the move velocity by the area to obtain the circulate velocity (continuity equation). A ruler or tape measure can be used to improve the accuracy of cross-sectional area measurements, and a stopwatch can be used to enhance velocity measurements by timing floating debris shifting a set distance. The eyeball method can be utilized to estimate move when solely an “order of magnitude” of circulate is required or when the move fee is just too low to be measured with a flow meter.
Flow depth (Manning)

When the channel cross-sectional space and channel slope are known and uniform flow conditions exist, the Manning’s equation can be utilized to calculate flow by measuring depth solely. The Manning’s equation is an empirical equation that describes the relationship between move price in an open channel under uniform flow situations and depth, slope and channel friction coefficient (Manning’s n). Uniform move signifies that depth does not vary with the size of the conduit or channel. Flow measurements utilizing Manning’s equation for depth are not relevant to gradually changing circulate situations, similar to backwater circumstances upstream of a dam or weir.
The depth circulate method of move measurement is more correct than the “eyeball” method. The primary challenge with depth-only move measurements is the potential for inaccurate Manning’s n estimates, cross-sectional areas, and non-uniform flow circumstances. This methodology is commonly used with ultrasonic flow meters to estimate the flow of a river by measuring only the water level of the river. Often in these causes, the river level/flow relationship is developed with the assistance of complex river hydraulic models to account for complex channel geometry and channel friction circumstances.
Main tools

The main device is used to measure move in open channels, utilizing buildings corresponding to flumes, weirs or dams, to measure flow by measuring depth. The measured depth can then be transformed to a flow rate utilizing an equation or rated curve equation.
Primary units work by forcing the circulate by way of a path of important depth, for instance at the top of a weir or on the throat of a flume. In technical phrases, the important depth is outlined as the depth of the minimal particular power state that results in a particular discharge. In apply, this minimal state of energy implies 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 gadgets are a very convenient technique of circulate measurement as a outcome of the depth can be measured from above the move with out the need to insert a sensor in the water. This makes main circulate meters more dependable and simpler to take care of. A drawback of primary gadgets is that they can trigger head loss and backwater in the system. Primary devices are sometimes thought-about to be the most accurate method of measuring open channel move.
Surface Velocity Meters

An space velocity meter is an open channel circulate meter that measures circulate by making two separate measurements of depth and velocity. The depth is transformed to a cross-sectional space utilizing the geometry of the pipe or channel. The move rate is then calculated by multiplying the flow area by the speed utilizing the continuity equation, therefore the identify “AV meter”. Velocity is often measured using a Doppler sensor, which reflects ultrasound waves again from particles within the fluid and uses the Doppler shift in the mirrored sound sign to estimate velocity. Some AV meters measure floor velocity optically to estimate velocity.
AV meters are sometimes used to measure open channel circulate in sewers as a outcome of the probes are relatively small and they can be put in in existing sewer pipes with out inflicting vital head loss in the pipe. This additionally allows them to be used for short-term or short-term circulate metering applications for sewer studies. one disadvantage of AV meters is that the sensor have to be put in within the fluid. In sewers, this requires frequent upkeep to scrub the sensor. AV meters are often considered less accurate than primary flow meters as a end result of primary devices only must measure depth and depth measurements are more correct than velocity measurements.
Transport time meters

Transport time meters have been developed within the oil trade to precisely measure circulate in giant pipelines. They have been used with some success for open channel circulate in water metering purposes. Transport time meters also use ultrasound like Doppler meters, but as an alternative of bouncing the sound waves off particles within the water like Doppler circulate meters, they ship ultrasound waves between two sensors separated from each other by a certain distance alongside the size of the pipe and uses the transmission time of the sound waves to calculate the speed of the water move. Because the velocity of sound in the water is understood, the pace of the water can be calculated primarily based on the offset in ultrasonic wave transmission time that occurs as a result of pace of the water.
Transmission time meters could be costly relative to Doppler circulate meters because of the many sensors and complicated installation concerned. They may be more correct due to the ability to separate the flow into horizontal cross sections and measure the speed of every part.
Flow unit measurement strategies in full tube functions

Venturi meters

Venturi flow meters use the Venturi effect to measure circulate in a full or pressurized pipe through the use of the converging section of the pipe to restrict the circulate. According to the continuity equation, the cross-sectional area of the converging section is small and due to this fact the velocity is higher in the throat. Due to energy conservation and Bernoulli’s principle, greater velocities in the throat result in a drop in throat pressure. The circulate price can then be determined by measuring the strain drop within the convergent section and calculating the circulate rate utilizing Bernoulli’s equation. Venturi meters are extra widespread in water metering functions because the pressure measurement ports can turn into clogged in wastewater purposes.
Magnetic flowmeter

The electromagnetic circulate meter works by making use of a magnetic field to the fluid passing by way of the pipe. This causes a small electron potential distinction that can be measured by the electrode sensor (due to Faraday’s legislation and electromagnetic induction). The magnitude of the electron potential distinction is proportional to the velocity of the water, and the continuity equation can then be used to calculate the move rate.
An benefit of the magnetometer is that the metering section is identical diameter because the adjoining pipe, so the magnetometer causes no extra head loss. For probably the most half, magnetometers are used for full (pressure) pipe purposes, however these days open channel magnetometers can be used.
Turbine flowmeter

A turbine circulate meter is a mechanical flow meter that uses a rotating turbine in move to measure the circulate of water in a pipe. The speed of the turbine is proportional to the rate and the move fee can then be calculated utilizing the continuity equation. Turbine flow meters are solely used for water purposes due to potential issues with wastewater solids assortment and clogging generators.
Conclusion

There are some ways to measure flow. Each method has completely different benefits, disadvantages and accuracy in different purposes.
It is important to grasp the traits of various flow measurement methods to assist select the right type of move metering for your utility or to properly interpret the flow measurements of existing move meters. Tools like Apure (IoT-based water data analysis) help to examine measurements collected by move meters and carry out diagnostics to understand circulate meter efficiency and rapidly process and analyze the info. Contact us for technical or product service support.
More articles on flow meters:
Mass circulate price vs volumetric flow fee

Relation between move and strain

Ultrasonic flow meter working principle

Difference between circulate meter and circulate transmitter
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Table of Contents

What is circulate units?

Continuity of circulate equation

Common move unit metering methods in open channels

Eyeball technique

Flow depth (Manning)

Main tools

Surface Velocity Meters

Transport time meters

Flow unit measurement strategies in full tube purposes

Venturi meters

Magnetic flowmeter

Turbine flowmeter

Conclusion

What is circulate units?

Flow fee is the volume of fluid that passes via a unit of time. In water resources, move is often measured in cubic toes per second (cfs), cubic meters per second (cms), gallons per minute (gpm), or a selection of other models. The measurement of water resource circulate is necessary for purposes corresponding to system control, billing, design and plenty of different purposes. There are several methods to measure circulate in a water resource system. This article outlines a few of the extra widespread methods of move measurement and offers some useful details about flow models measurement.
Continuity of move equation

For water flowing in a pipe underneath steady-state circumstances (i.e., not various with time), continuity means that water flowing into one finish of the pipe must flow out of the opposite finish. This additionally implies that the move in the pipe is identical at any point along the length of the pipe. The continuity equation may be expressed as

Flow = Velocity * Area

The idea of continuity in steady state situations ends in the product of velocity * area being equal to a relentless at any level within the pipe. This is a useful principle for making move measurements, as proven beneath.
This is an example of utilizing the continuity equation to calculate move. Velocity is measured at 10 ft per second and the cross-sectional space of the flow is measured at 10 square feet. Flow fee = 10 toes per second * 10 square ft = 100 cubic ft per second.
Common move unit metering strategies in open channels

Eyeball technique

It is sometimes helpful to estimate the circulate velocity and cross-sectional space by eye and then multiply the flow velocity by the realm to acquire the move 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 improve velocity measurements by timing floating debris transferring a set distance. The eyeball method can be utilized to estimate circulate when only an “order of magnitude” of move is required or when the move fee is too low to be measured with a flow meter.
Flow depth (Manning)

When the channel cross-sectional space and channel slope are recognized and uniform circulate situations exist, the Manning’s equation can be utilized to calculate flow by measuring depth solely. The Manning’s equation is an empirical equation that describes the connection between circulate rate in an open channel under uniform flow situations and depth, slope and channel friction coefficient (Manning’s n). Uniform flow signifies that depth does not vary with the length of the conduit or channel. Flow measurements utilizing Manning’s equation for depth aren’t applicable to progressively changing flow conditions, similar to backwater situations upstream of a dam or weir.
The depth flow technique of move measurement is extra correct than the “eyeball” methodology. The major problem with depth-only flow measurements is the potential for inaccurate Manning’s n estimates, cross-sectional areas, and non-uniform circulate circumstances. This methodology is often used with ultrasonic move meters to estimate the flow 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 help of advanced river hydraulic fashions to account for complex channel geometry and channel friction circumstances.
Main equipment

The major device is used to measure move in open channels, using buildings similar to flumes, weirs or dams, to measure flow by measuring depth. The measured depth can then be transformed to a circulate rate utilizing an equation or rated curve equation.
Primary gadgets work by forcing the flow through a path of critical depth, for instance on the high of a weir or on the throat of a flume. In technical terms, the crucial depth is outlined because the depth of the minimal specific energy state that leads to a specific discharge. In follow, this minimal state of energy implies that just one move corresponds to the critical depth. Therefore, measuring solely the depth produces a measurement of the corresponding flux and is subsequently known as a “primary” gadget.
Primary units are a very convenient method of circulate measurement as a result of the depth can be measured from above the move with out the necessity to insert a sensor within the water. This makes major move meters extra dependable and simpler to take care of. A drawback of main gadgets is that they can cause head loss and backwater within the system. Primary devices are sometimes thought of to be the most correct method of measuring open channel move.
Surface Velocity Meters

An space velocity meter is an open channel circulate meter that measures move by making two separate measurements of depth and velocity. The depth is transformed to a cross-sectional area utilizing the geometry of the pipe or channel. The move fee is then calculated by multiplying the move space by the velocity using the continuity equation, therefore the identify “AV meter”. Velocity is often measured using a Doppler sensor, which displays ultrasound waves back from particles in the fluid and makes use of the Doppler shift in the mirrored sound signal to estimate velocity. Some AV meters measure surface velocity optically to estimate velocity.
AV meters are often used to measure open channel circulate in sewers because the probes are comparatively small and they can be installed in current sewer pipes with out inflicting vital head loss in the pipe. This also allows them to be used for short-term or short-term circulate metering purposes for sewer research. one disadvantage of AV meters is that the sensor should be put in in the fluid. In sewers, this requires frequent upkeep to clean the sensor. AV meters are often considered less correct than main circulate meters as a end result of major gadgets solely must measure depth and depth measurements are extra accurate than velocity measurements.
Transport time meters

Transport time meters had been developed within the oil business to precisely measure move in large pipelines. They have been used with some success for open channel move in water metering purposes. Transport time meters additionally use ultrasound like Doppler meters, but as an alternative of bouncing the sound waves off particles within the water like Doppler move meters, they send ultrasound waves between two sensors separated from one another by a sure distance alongside the size of the pipe and uses the transmission time of the sound waves to calculate the velocity of the water circulate. Because the speed of sound in the water is known, the velocity of the water can be calculated based on the offset in ultrasonic wave transmission time that occurs due to the pace of the water.
Transmission time meters could be costly relative to Doppler move meters due to the many sensors and complicated set up involved. They could be extra accurate because of the capability to split the move into horizontal cross sections and measure the rate of each part.
Flow unit measurement methods in full tube purposes

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 subsequently the speed is greater within the throat. Due to vitality conservation and Bernoulli’s precept, greater velocities in the throat end in a drop in throat strain. The flow rate can then be determined by measuring the pressure drop within the convergent part and calculating the circulate fee using Bernoulli’s equation. Venturi meters are extra widespread in water metering functions because the strain measurement ports can turn into clogged in wastewater purposes.
Magnetic flowmeter

The electromagnetic move meter works by applying a magnetic area to the fluid passing by way of the pipe. This causes a small electron potential distinction that could 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 circulate price.
An benefit of the magnetometer is that the metering section is similar diameter because the adjoining pipe, so the magnetometer causes no further head loss. For the most half, magnetometers are used for full (pressure) pipe purposes, but nowadays open channel magnetometers can additionally be used.
Turbine flowmeter

A turbine flow meter is a mechanical move meter that uses a rotating turbine in flow to measure the move of water in a pipe. The pace of the turbine is proportional to the speed and the circulate rate can then be calculated using the continuity equation. Turbine flow meters are only used for water purposes because of potential problems with wastewater solids assortment and clogging turbines.
Conclusion

There are many ways to measure move. Each method has completely different benefits, disadvantages and accuracy in numerous purposes.
It is necessary to understand the traits of varied circulate measurement methods to help choose the right type of move metering in your software or to correctly interpret the circulate measurements of current flow meters. Tools like Apure (IoT-based water data analysis) assist to look at measurements collected by circulate meters and carry out diagnostics to know circulate meter performance and quickly process and analyze the information. Contact us for technical or product service help.
ไดอะแฟรม ซีล on circulate meters:
Mass flow price vs volumetric circulate rate

Relation between move and stress

Ultrasonic move meter working principle

Difference between flow meter and move transmitter

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