Table of Contents
What is move units?
Continuity of move equation
Common circulate unit metering methods in open channels
Eyeball methodology
Flow depth (Manning)
Main gear
Surface Velocity Meters
Transport time meters
Flow unit measurement strategies in full tube purposes
Venturi meters
Magnetic flowmeter
Turbine flowmeter
Conclusion
What is flow units?
Flow rate is the quantity of fluid that passes through a unit of time. In water sources, flow is commonly measured in cubic feet per second (cfs), cubic meters per second (cms), gallons per minute (gpm), or a selection of other models. The measurement of water resource flow is necessary for purposes similar to system control, billing, design and lots of other purposes. There are a quantity of methods to measure move in a water resource system. This article outlines some of the extra widespread methods of flow measurement and offers some helpful details about flow models measurement.
Continuity of flow equation
For water flowing in a pipe beneath steady-state situations (i.e., not varying with time), continuity means that water flowing into one end of the pipe must move out of the opposite end. This additionally signifies that the circulate in the pipe is the same at any level alongside the length of the pipe. The continuity equation could be expressed as
Flow = Velocity * Area
The idea of continuity in regular state conditions ends in the product of velocity * area being equal to a relentless at any point in the pipe. This is a useful precept for making move measurements, as proven below.
This is an instance of utilizing the continuity equation to calculate circulate. Velocity is measured at 10 feet per second and the cross-sectional area of the circulate is measured at 10 sq. toes. Flow fee = 10 ft per second * 10 square feet = 100 cubic ft per second.
Common circulate unit metering methods in open channels
Eyeball method
It is typically useful to estimate the circulate velocity and cross-sectional space by eye and then multiply the circulate velocity by the world to acquire the move velocity (continuity equation). A ruler or tape measure can be used to improve the accuracy of cross-sectional space measurements, and a stopwatch can be utilized to enhance velocity measurements by timing floating particles transferring a set distance. The eyeball technique can be used to estimate circulate when solely an “order of magnitude” of flow is required or when the move price is too low to be measured with a circulate meter.
Flow depth (Manning)
When the channel cross-sectional space and channel slope are identified and uniform move situations exist, the Manning’s equation can be used to calculate circulate 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 move conditions and depth, slope and channel friction coefficient (Manning’s n). Uniform flow implies that depth does not differ with the length of the conduit or channel. Flow measurements utilizing Manning’s equation for depth aren’t applicable to progressively altering circulate circumstances, similar to backwater conditions upstream of a dam or weir.
The depth flow methodology of flow measurement is more accurate than the “eyeball” technique. The primary challenge with depth-only circulate measurements is the potential for inaccurate Manning’s n estimates, cross-sectional areas, and non-uniform move circumstances. This technique is commonly used with ultrasonic circulate meters to estimate the circulate 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 assistance of complex river hydraulic fashions to account for complicated channel geometry and channel friction situations.
Main gear
The primary gadget is used to measure flow in open channels, utilizing buildings similar to flumes, weirs or dams, to measure move by measuring depth. The measured depth can then be converted to a circulate rate using an equation or rated curve equation.
Primary devices work by forcing the flow by way of a path of crucial depth, for example on the top of a weir or at the throat of a flume. In technical phrases, the critical depth is defined because the depth of the minimum specific energy state that results in a specific discharge. In apply, this minimum state of energy means that only one flow corresponds to the important depth. Therefore, measuring only the depth produces a measurement of the corresponding flux and is subsequently called a “primary” gadget.
Primary devices are a really handy technique of flow measurement because the depth could be measured from above the flow without the necessity to insert a sensor in the water. This makes primary flow meters extra dependable and simpler to keep up. A drawback of main devices is that they can cause head loss and backwater in the system. Primary gadgets are sometimes thought of to be the most accurate technique of measuring open channel circulate.
Surface Velocity Meters
An space 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 utilizing the geometry of the pipe or channel. The flow rate is then calculated by multiplying the circulate area by the speed utilizing the continuity equation, hence the title “AV meter”. Velocity is often measured using a Doppler sensor, which displays ultrasound waves again from particles in the fluid and uses the Doppler shift within 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 circulate in sewers as a result of the probes are comparatively small and they can be put in in current sewer pipes with out inflicting vital head loss within the pipe. This also permits them to be used for momentary or short-term circulate metering applications for sewer studies. one drawback of AV meters is that the sensor must be installed within the fluid. In sewers, this requires frequent maintenance to scrub the sensor. AV meters are sometimes thought-about less accurate than major move meters because main devices solely need to 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 accurately measure move in massive pipelines. They have been used with some success for open channel flow in water metering purposes. Transport time meters additionally use ultrasound like Doppler meters, but instead of bouncing the sound waves off particles in the water like Doppler circulate meters, they send ultrasound waves between two sensors separated from each other 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 pace of sound within the water is known, the speed of the water can be calculated based mostly on the offset in ultrasonic wave transmission time that occurs as a end result of velocity of the water.
Transmission time meters can be costly relative to Doppler move meters because of the many sensors and complicated installation involved. They may be extra correct as a outcome of capability to split the move into horizontal cross sections and measure the velocity of each part.
Flow unit measurement strategies in full tube purposes
Venturi meters
Venturi move meters use the Venturi effect to measure move in a full or pressurized pipe by using the converging section of the pipe to restrict the flow. According to the continuity equation, the cross-sectional space of the converging section is small and therefore the rate is higher in the throat. Due to energy conservation and Bernoulli’s principle, higher velocities within the throat end in a drop in throat pressure. The circulate price can then be decided by measuring the stress drop within the convergent part and calculating the circulate fee using Bernoulli’s equation. Venturi meters are extra widespread in water metering applications because the strain measurement ports can become clogged in wastewater functions.
pressure gauge 10 bar by making use of a magnetic field to the fluid passing through the pipe. ไดอะแฟรม ซีล 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 distinction is proportional to the speed of the water, and the continuity equation can then be used to calculate the circulate price.
An advantage of the magnetometer is that the metering part is similar diameter as the adjoining pipe, so the magnetometer causes no extra head loss. For essentially the most half, magnetometers are used for full (pressure) pipe purposes, but nowadays open channel magnetometers can be used.
Turbine flowmeter
A turbine move meter is a mechanical circulate meter that uses a rotating turbine in circulate to measure the move of water in a pipe. The velocity of the turbine is proportional to the velocity and the circulate price 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 some ways to measure circulate. Each technique has completely different advantages, disadvantages and accuracy in several purposes.
It is important to understand the traits of varied flow measurement strategies to assist choose the proper sort of flow metering on your utility or to correctly interpret the flow measurements of current flow meters. Tools like Apure (IoT-based water knowledge analysis) assist to look at measurements collected by move meters and perform diagnostics to grasp move meter performance and quickly course of and analyze the data. Contact us for technical or product service assist.
More articles on move meters:
Mass circulate rate vs volumetric move price
Relation between move and stress
Ultrasonic move meter working principle
Difference between move meter and circulate transmitter
All the numerous particulars to keep in mind that come with #keyword# could be enough to bring on a major headache. Once you have your resolve, and a firm photo of your goal in mind, just work through the steps one by one. Help with just about any subject matter can be found on the web. That said, the site that I advocate, that will offer you the most help at this point, is #links#.
Table of Contents
What is circulate units?
Continuity of move equation
Common move unit metering methods in open channels
Eyeball technique
Flow depth (Manning)
Main gear
Surface Velocity Meters
Transport time meters
Flow unit measurement methods in full tube purposes
Venturi meters
Magnetic flowmeter
Turbine flowmeter
Conclusion
What is circulate units?
Flow price is the amount of fluid that passes through a unit of time. In water assets, move is usually measured in cubic feet per second (cfs), cubic meters per second (cms), gallons per minute (gpm), or a wide selection of different items. The measurement of water resource circulate is essential for purposes such as system control, billing, design and many different applications. There are several ways to measure flow in a water resource system. This article outlines a number of the extra frequent methods of circulate measurement and provides some useful information about move units measurement.
Continuity of flow equation
For water flowing in a pipe beneath steady-state situations (i.e., not varying with time), continuity signifies that water flowing into one finish of the pipe must flow out of the opposite end. This additionally means that the move within the pipe is similar at any level along the length of the pipe. The continuity equation could 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 relentless at any level in the pipe. This is a helpful precept for making flow measurements, as proven below.
This is an instance of using the continuity equation to calculate flow. Velocity is measured at 10 feet per second and the cross-sectional area of the flow is measured at 10 square toes. Flow rate = 10 ft per second * 10 square toes = one hundred cubic toes per second.
Common circulate unit metering methods in open channels
Eyeball method
It is usually helpful to estimate the flow velocity and cross-sectional area by eye and then multiply the flow velocity by the realm to acquire 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 used to improve velocity measurements by timing floating particles shifting a set distance. The eyeball technique can be utilized to estimate move when solely an “order of magnitude” of move 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 area and channel slope are known and uniform move situations exist, the Manning’s equation can be used to calculate move by measuring depth solely. The Manning’s equation is an empirical equation that describes the relationship between move price in an open channel beneath uniform move circumstances and depth, slope and channel friction coefficient (Manning’s n). Uniform move implies that depth doesn’t range with the length of the conduit or channel. Flow measurements utilizing Manning’s equation for depth aren’t relevant to progressively altering flow conditions, corresponding to backwater circumstances upstream of a dam or weir.
The depth circulate methodology of move measurement is extra correct than the “eyeball” method. The major problem with depth-only circulate measurements is the potential for inaccurate Manning’s n estimates, cross-sectional areas, and non-uniform move circumstances. This method is usually used with ultrasonic move meters to estimate the flow 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 assistance of complicated river hydraulic models to account for complex channel geometry and channel friction situations.
Main gear
The primary gadget is used to measure move in open channels, using structures similar to flumes, weirs or dams, to measure circulate by measuring depth. The measured depth can then be transformed to a circulate price using an equation or rated curve equation.
Primary gadgets work by forcing the flow by way of a path of crucial depth, for instance at the top of a weir or on the throat of a flume. In technical terms, the crucial depth is outlined as the depth of the minimal specific energy state that ends in a specific discharge. In apply, this minimum state of energy means that just one circulate corresponds to the important depth. Therefore, measuring only the depth produces a measurement of the corresponding flux and is due to this fact known as a “primary” system.
Primary devices are a really convenient methodology of move measurement as a result of the depth could be measured from above the flow with out the want to insert a sensor within the water. This makes main circulate meters more dependable and simpler to maintain. A disadvantage of main devices is that they’ll trigger head loss and backwater in the system. Primary gadgets are often thought-about to be essentially the most accurate methodology of measuring open channel circulate.
Surface Velocity Meters
An space velocity meter is an open channel move meter that measures circulate by making two separate measurements of depth and velocity. The depth is converted 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 velocity using the continuity equation, therefore the identify “AV meter”. Velocity is usually measured using a Doppler sensor, which displays ultrasound waves back from particles within the fluid and uses the Doppler shift within 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 flow in sewers as a end result of the probes are comparatively small and they are often put in 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 applications for sewer studies. one disadvantage of AV meters is that the sensor must be put in in the fluid. In sewers, this requires frequent maintenance to scrub the sensor. AV meters are often considered less correct than main flow meters as a result of main gadgets solely need to measure depth and depth measurements are more correct than velocity measurements.
Transport time meters
Transport time meters were developed within the oil trade to accurately measure circulate in giant pipelines. They have been used with some success for open channel move in water metering applications. Transport time meters also use ultrasound like Doppler meters, but as an alternative of bouncing the sound waves off particles in the water like Doppler circulate meters, they send ultrasound waves between two sensors separated from one another by a sure distance alongside the length of the pipe and makes use of the transmission time of the sound waves to calculate the velocity of the water circulate. Because the pace 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 due to the speed of the water.
Transmission time meters can be costly relative to Doppler flow meters because of the many sensors and complex installation involved. They can be extra accurate because of the capability to split the move into horizontal cross sections and measure the velocity of each part.
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 limit the circulate. According to the continuity equation, the cross-sectional area of the converging section is small and therefore the speed is greater within the throat. Due to energy conservation and Bernoulli’s principle, higher velocities within the throat result in a drop in throat stress. The circulate rate can then be decided by measuring the strain drop within the convergent part and calculating the flow price using Bernoulli’s equation. Venturi meters are extra widespread in water metering purposes as a outcome of the pressure measurement ports can turn into clogged in wastewater applications.
Magnetic flowmeter
The electromagnetic circulate meter works by applying a magnetic field to the fluid passing via the pipe. This causes a small electron potential distinction that might be measured by the electrode sensor (due to Faraday’s law 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 fee.
An advantage of the magnetometer is that the metering section is similar diameter because the adjacent pipe, so the magnetometer causes no additional head loss. For the most part, magnetometers are used for full (pressure) pipe functions, but nowadays open channel magnetometers can also be used.
Turbine flowmeter
A turbine move meter is a mechanical flow meter that makes use of a rotating turbine in circulate to measure the circulate of water in a pipe. The velocity of the turbine is proportional to the velocity and the flow fee can then be calculated using the continuity equation. Turbine circulate meters are only used for water functions as a result of potential issues with wastewater solids assortment and clogging generators.
Conclusion
There are some ways to measure move. Each methodology has totally different benefits, disadvantages and accuracy in several applications.
It is essential to understand the traits of assorted move measurement techniques to assist select the proper type of flow metering in your application or to correctly interpret the circulate measurements of existing flow meters. Tools like Apure (IoT-based water knowledge analysis) assist to examine measurements collected by flow meters and carry out diagnostics to grasp move meter performance and rapidly course of and analyze the info. Contact us for technical or product service assist.
More articles on flow meters:
Mass circulate rate vs volumetric circulate rate
Relation between circulate and pressure
Ultrasonic circulate meter working precept
Difference between flow meter and flow transmitter