Flowmeter ini dikenal juga sebagai vortex shedding flowmeters atau oscillatory flowmeters, Flowmeter jenis Vortex biasa diaplikasikan hampir pada semua liquid dan gas bahkan steam, dan dibeberapa flowmeter sudah ditanamkan sensor temperature PT-100 sehingga untuk steam hasil bacanya sudah bisa berupa konversi ke satuan massa, dan untuk Compressed gas tinggal ditambah Presure transmitter yang diintegrasikan pada metering system.
Kelebihan Flowmeter jenis Vortex :
- Bisa mengukur hampir semua jenis liquid
- tidak ada benda yang bergerak atau berputar sehingga mengurangi resiko terjadinya Zero-point drift pada pembacaan
Minimum inlet and outlet runs with various flow obstructions
A = Inlet run
B = Outlet run
h = Difference in expansion
1 = Reduction
2 = Extension
3 = 90° elbow or T-piece
4 = 2 × 90° elbow, 3-dimensional
5 = 2 × 90° elbow
6 = Control valve
A = Inlet run
B = Outlet run
h = Difference in expansion
1 = Reduction
2 = Extension
3 = 90° elbow or T-piece
4 = 2 × 90° elbow, 3-dimensional
5 = 2 × 90° elbow
6 = Control valve
ALIA Votex Flowmeter
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The Vortex Flowmeter
Design Overview: At 11 a.m. on November 7th, 1940 the Tacoma Narrows suspension bridge in the state of Washington collapsed from wind-induced vibrations. The torsional motion of the bridge shortly before its collapse is an indication of the power of vortex shedding. The prevailing theory on the collapse of the bridge is that the oscillations were caused by the shedding of turbulent vortices in a periodic manner. Experimental observations have in fact shown that broad flat obstacles (also referred to as bluff bodies) produce periodic swirling vortices which generate high and low pressure regions directly behind the bluff body. The rate at which these vortices shed is given by the following equation:
f = SV/L
where,
f = the frequency of the vortices
L = the characteristic length of the bluff body
V = the velocity of the flow over the bluff body
S = Strouhal Number and is a constant for a given body shape
In the case of the Tacoma bridge, a wind speed of approximately 40 mph caused the formation of vortices around the 8-ft.-deep, steel plate girders of the bridge. This established vortices which were shed, according to the above equation, at approximately 1 Hz. As the structural oscillations constructively reinforced, the bridge began oscillating, building up amplitude, until it could no longer hold itself together.
Another less tragic example of the vortex principle can be seen in the waving motion of a flag. The flag pole, acting as a bluff body, creates swirling vortices behind it that give the flag its "flapping" quality in strong winds.
A practical application of vortex production can be found in the
design of the vortex flowmeter. In this design, a bluff body or bodies
is placed within the fluid stream. Just behind the bluff body, a
pressure transducer, thermistor, or ultrasonic sensor picks up the high
and low pressure and velocity fluctuations as the vortices move past the
sensor (Figure 5). These fluctuations are linear, directly proportional
to the flowrate and independent of fluid density, pressure, temperature
and viscosity (within certain limits). As given explicitly in the above
equation, the frequency of the vortices is directly proportional to the
velocity of the fluid. Vortex meters are very flexible and the
technology can be used for liquid, gas and steam measurements. This,
along with the fact that they have no moving parts, makes them a very
popular choice. Accuracies are typically in the ±1% range.
Generally speaking, in-line vortex meters are available in line sizes ranging from 1/2 to 16". Insertion vortex meters that are installed in the top or sides of a pipe can be used for even larger pipe sizes. This makes them versatile in a wide variety of applications (Figure 6).
One final remark concerns the Reynolds number limitations for these flowmeters. For vortex meters, vortices will not be shed under a Reynolds number of approximately 2000. From roughly 2000 to 10,000, vortices will be shed but the resulting fluctuations are non-linear in this range. Typically, a minimum Reynolds number of 10,000 is required in order get optimum performance from the vortex flowmeter. This number can vary from one design to another, so it is advisable to check with the manufacturer.
Advantages: The advantages of a vortex meter are many. They are summarized below:
In addition to the above, be aware that a minimum length of straight-run pipe is required upstream and downstream of the meter for the accurate creation of vortices within the flowmeter. Ten pipe diameters before and after the point of installation are typically recommended, but the minimum length could be greater if there are elbows or valves nearby. This is only a disadvantage if the installation area does not allow for this straight run of pipe.
Applications: Vortex meters have become extremely popular in recent years and are used in a variety of applications and industries. Below is a summary of some of the main uses of a vortex meter.
The Vortex Flowmeter
Design Overview: At 11 a.m. on November 7th, 1940 the Tacoma Narrows suspension bridge in the state of Washington collapsed from wind-induced vibrations. The torsional motion of the bridge shortly before its collapse is an indication of the power of vortex shedding. The prevailing theory on the collapse of the bridge is that the oscillations were caused by the shedding of turbulent vortices in a periodic manner. Experimental observations have in fact shown that broad flat obstacles (also referred to as bluff bodies) produce periodic swirling vortices which generate high and low pressure regions directly behind the bluff body. The rate at which these vortices shed is given by the following equation:
f = SV/L
where,
f = the frequency of the vortices
L = the characteristic length of the bluff body
V = the velocity of the flow over the bluff body
S = Strouhal Number and is a constant for a given body shape
In the case of the Tacoma bridge, a wind speed of approximately 40 mph caused the formation of vortices around the 8-ft.-deep, steel plate girders of the bridge. This established vortices which were shed, according to the above equation, at approximately 1 Hz. As the structural oscillations constructively reinforced, the bridge began oscillating, building up amplitude, until it could no longer hold itself together.
Another less tragic example of the vortex principle can be seen in the waving motion of a flag. The flag pole, acting as a bluff body, creates swirling vortices behind it that give the flag its "flapping" quality in strong winds.
 |
| Figure 5 As fluid moves around the baffles, vortices form and move downstream. The frequency of the vortices is directly proportional to the flowrate. |
Generally speaking, in-line vortex meters are available in line sizes ranging from 1/2 to 16". Insertion vortex meters that are installed in the top or sides of a pipe can be used for even larger pipe sizes. This makes them versatile in a wide variety of applications (Figure 6).
One final remark concerns the Reynolds number limitations for these flowmeters. For vortex meters, vortices will not be shed under a Reynolds number of approximately 2000. From roughly 2000 to 10,000, vortices will be shed but the resulting fluctuations are non-linear in this range. Typically, a minimum Reynolds number of 10,000 is required in order get optimum performance from the vortex flowmeter. This number can vary from one design to another, so it is advisable to check with the manufacturer.
- No moving parts to wear
- No routine maintenance required
- Can be used for liquids, gases, and steam
- Stable long term accuracy and repeatability
- Lower cost of installation than traditional orifice-type meters
- Available in a wide variety of temperature ranges from -300F to roughly 800F
- Bar-like bluff design allows particulates to pass through without getting clogged
- Available for a wide variety of pipe sizes
- Available in a wide variety of communication protocols
In addition to the above, be aware that a minimum length of straight-run pipe is required upstream and downstream of the meter for the accurate creation of vortices within the flowmeter. Ten pipe diameters before and after the point of installation are typically recommended, but the minimum length could be greater if there are elbows or valves nearby. This is only a disadvantage if the installation area does not allow for this straight run of pipe.
Applications: Vortex meters have become extremely popular in recent years and are used in a variety of applications and industries. Below is a summary of some of the main uses of a vortex meter.
- Custody transfer of natural gas metering
- Flow of liquid suspensions
- Higher viscosity fluids
- Steam measurement
- General water applications
- Chilled and hot water
- Water/glycol mixtures
- Condensate measurement
- Potable water
- Ultrapure & de-ionized water
- Acids
- Solvents
