Vortex flow meters have many applications from water to gas, but one of the most common is for steam flow measurement. Although multivariable pressure transmitters are still the most popular choice, some new vortex flow meters have advanced features that make them more appealing for certain applications.
Here, we shall talk about the working principle of vortex flow meters and how is it applicable in the measurement of steam flow.
To know about the types of flow meters in the industry, you can read our article on flow meter types
Vortex flow meter applications
Vortex flow meters operate under the vortex shedding principle, where an oscillating vortexes occur when a fluid such as water flow past a bluff body. On the downside, they have certain unavoidable limits, like pressure drop and installation needs. On the upside, you get flexibility, accuracy, and advantages like steam quality measurement.
The history of vortex flow meters
It all began in 1513, when the great Leonardo da Vinci created the first draft of vortices downstream of objects shedding flow. A few years later in 1878, Czech Vincenc Strouhal developed a scientific form to explain the eddies created after bluff bodies Basically, a wire stretched tight in a jet of air will vibrate, and its frequency is directly proportional to the velocity of the air jet.
This equation will find the Strouhal number, the relationship between the velocity of flow, vortex shedding frequency, and diameter of the bluff body. In 1912, the physicist Theodore von Kárman used this concept in flow measurement, and we now call his description of the Kárman vortex street.
The vortex flow meter’s working principle
All vortex flow meters have an obstacle, called the bluff body, in front of the measuring sensor. When flow goes through the pipe, the bluff body creates eddies in the vortex street.
The frequency on each side of the bluff body is directly proportional to the flow velocity and volume flow. However, this phenomenon requires a minimum Reynolds number to generate those frequencies.
What does Reynolds number mean? Well, it has to do with inertial and viscous forces and can forecast the turbulence in the flow.
Bluff body types
Vortex flow meters use bluff bodies to break up the flow enough to create eddies. Bluff body types and shapes will vary among vendors. Vendors even have patents for them, because some will result in flow meters offering less pressure loss, others in lower measuring range, and so on.
Want to read about the Coriolis flow meter, you can check out our article on Coriolis
Volume and mass flow meters
The vortex flow meter can measure a variety of fluid products. However, the meter itself measures volume flow. So to measure mass, we have additional features to allow accurate measurement.
When we need just the numbers for volume flow, the meter can measure that directly. For instance, if we have water flow in an application that doesn’t have the conductivity an electromagnetic flow meter needs, then we can use a vortex flow meter.
For mass flow, a vortex flow meter must have a component to calculate the measurement as well as a temperature sensor. In some applications, you need a pressure transmitter too. Some vendors build all of these into their vortex meters, and others may only include a couple and have the rest as add-ons. If one needs mass flow, then you should check what your vortex meter has to do that.
The best vortex flow meters on the market
Below are some of the main vendors of vortex flow meters. To know more, you can read our article on the best Vortex flow meters
Foxboro is a household name in the instrumentation world, owned by Schneider today. The 83S is a universal flow meter, so we can apply it in many processes.
Endress+Hauser Prowirl F 200
Endress+Hauser has included a lot of fancy features in this meter, the “steam specialist.” We reviewed this product, and you can read that here. E+H also has different models to fit your flow application.
Another household name in instrumentation, Yokogawa didn’t launch many new features with this meter, but it promises reduced costs in a plant, which always sounds good.
If you need help choosing the right flow meter for your application, take a look at our new flow smart assistant.
To know more about vortex flow meters, you can get in touch with our engineers!