Swirl Flowmeter vs. Vortex Flowmeter: Key Differences

This article explores the differences between swirl flowmeters and vortex flowmeters, two types of devices used to measure fluid flow rates. While both operate on similar principles, their construction and performance characteristics differ.

Swirl Flowmeter

• Image Alt: Swirl Flowmeter

Swirl flowmeters are versatile instruments suitable for measuring the flow of various liquids, gases, and steam. They bear resemblance to vortex flowmeters but feature a distinct construction. Like vortex flowmeters, swirl flowmeters can be used for direct mass flow measurement of dry saturated steam.

Here’s how they work:

• Principle: They operate on the principle of pressure variations caused by interrupting the fluid flow with an obstruction, similar to the vortex principle.
• Swirl Generation: The flow passes through fixed spiral vanes. This creates a spiral flow pattern across the entire pipe.
• Flow Rate Measurement: The frequency of fluid rotation is directly related to the flow rate. A sensor detects the speed of this rotation, and the information is sent to the flowmeter’s electronic circuits.
• Performance: Swirl flowmeters are known for their accuracy and robustness, functioning well in harsh process and environmental conditions. They typically offer accuracy on the order of +/- 0.2%.

Vortex Flowmeter

• Image Alt: Vortex Flow Meter

Vortex flowmeters leverage a natural phenomenon that occurs when fluid flows around a bluff (or non-streamlined) object.

• Principle: As fluid flows past the object, vortices (swirling patterns) are shed alternately downstream, similar to a flag flapping in the breeze. The frequency of this “shedding” is proportional to the fluid velocity. The more frequent the shedding, the higher the flow rate.
• Components: A vortex flowmeter consists of a flow tube and a transmitter. The flow tube itself has a body, a shedder (the bluff object), and sensors.
• Performance and Installation: Vortex flowmeters are commonly used with liquids, gases and steam with accuracy requirements of about +/- 0.75%.
  • Pipe Sizes: Typically available for pipe sizes from 2” to 20”.
  • Fluid Compatibility: Suitable for both clean and dirty water.
  • Pressure Loss: They exhibit low to medium pressure loss.
  • Accuracy: Accuracy is around +/- 1% of full scale.
  • Straight Pipe Requirements: They need straight pipe lengths upstream of about 10 times the diameter and downstream about 5 times the diameter.
  • Cost: They are typically low to medium in cost.

Core Differences Summarized

In summary, swirl flowmeters offer higher accuracy and are better suited for high-viscosity fluids and installations with limited straight pipe runs compared to vortex flowmeters. Both types of flowmeters play important roles in various industrial measurement applications.