Dual tees or the combination of an elbow and tee in a plane can cause unpredictable behaviour in a measurement application – sometimes more than what’s initially discovered during the design and testing phases.
Because tees are known for their tighter radius of turn, they can cause several problems, from the flow disconnecting from the pipe wall, to generating vortices and causing intense turbulence, and more.
So this got us thinking…What is the true value of adding in a flow conditioner? And how much does it matter?
We set out to answer these questions by running a computational fluid dynamics (CFD) case study on flow conditioning by exploring the effects of typical real world piping configurations with and without a flow conditioner.
We were especially curious about what happens when you use an ultrasonic flow meter with different path configurations, including a:
- 4-path ultrasonic
- 4-path ultrasonic variation 2
- 8-path ultrasonic
- 15-path ultrasonic
And the results are in. Here’s the verdict:
What happens to a single elbow and tee without flow conditioning
In an application with no flow conditioning, measurements were taken at 10D downstream of the tee, resulting in a 10D total length meter tube.
First, we noticed dramatic behaviour in the flow that made the measurement quite challenging. The average flow velocity through the pipe was unstable at 5D from the meter inlet, and the average velocity varied by up to 1.6%.
Then as we moved further down the meter tube, the stability improved but only at the cost of requiring a much longer tube (20 pipe diameters). If that didn’t complicate things enough, we also saw problems from the impact of the velocity stability on flow velocity measured by the flow meter.
When we evaluated the performance of the meter installed 10D from the inlet, these were the results:
- The 4-path variation 1 meter has an average of 2.76% error
- The 4-path variation 2 meter has an average of -2.21% error
- The 8-path has an average of 1.84% error
- The 15-path has an average of 1.39% error
When looking at the total average error range (maximum error – minimum error), we noticed that:
- The 4-path variation 1 meter has a range of 3.91% error
- The 4-path variation 2 meter has a range of 5.80% error
- The 8-path has a range of 3.73% error
- The 15-path has a range of 2.29% error
What happens to a single elbow and tee with flow conditioning
By contrast, when we introduced CPA 55E into the equation, we got a whole new set of results that speak for themselves. Again, a 10D total length meter tube was used, with the measurements being taken at 10D from the tee, but a flow conditioner was now installed at the halfway point in the tube, 5D from the inlet.
The addition of a flow conditioner enhanced the measurement by significantly improving the flow state in the meter tube. The vortex shedding that we initially saw in our application without a conditioner was impressively reduced in this simulation, and the variance in the average flow velocity was much smaller, only about a 0.40% total range instead.
There was hardly any deviation from the 5D to 20D pipe lengths, which reinforced the idea that the flow behaviour remained consistent down the length of the meter tube, unlike the application without a flow conditioner.
When we look at the performance of the meter installed 10D from the inlet, the results are vastly better than with no flow conditioning.
- The 4-path variation 1 meter has an average of -0.24% error
- The 4-path variation 2 meter has an average of 0.32% error
- The 8-path has an average of -0.21% error
- The 15-path has an average of -0.14 % error
When looking at the total average error range (maximum error – minimum error), we noticed that:
- The 4-path variation 1 meter has a range of 2.35% error
- The 4-path variation 2 meter has a range of 2.21% error
- The 8-path has a range of 2.36% error
- The 15-path has a range of 1.49% error
When we look at the performance of the meter installed 10D from the inlet, the results are vastly better than with no flow conditioning.
To see the full results and how flow conditioners improve flow state both in the lab and in the real world, check out our latest case study.
The Bottom Line
These simulations make it very clear: when faced with an upstream piping installation such as an elbow & tee, the use of a CPA 55E flow conditioner both improves the state of velocity flow in the pipe, and improves the quality of measurement from the ultrasonic meter itself.
When focusing on the state of the average pipe flow velocity, the addition of the CPA 55E reduces the variance in the velocity by up to 75% at 10 diameters from the meter tube inlet!
When looking at the specific performance of an ultrasonic flow meter, the use of a CPA 55E flow conditioner helps reduce the different meter errors by 85-92% and reduces the overall range of the error variance by 35-63%!
At Canada Pipeline Accessories, we build right and we build to last. Contact us for a free consultation, and we’ll help you solve your measurement & mixing problems today.
