3 replies to this topic

Hi all,
Do we have a constrain on the coriolis flow meter that the liquid passing through it must be its laminar state?Or it can measure the flow rate even in turbulent conditions?

[gvdlans]

I have never hear of such a constraint, and also don't see why the liquid flow should be laminar when looking at the Coriolis measurement principle (see for example Coriolis Flowmeters Overview ). I do know that Coriolis meters can have problems with 2-phase flow (vapour bubbles in the liquid).

[djack77494]

Coriolis meters should be able to handle laminar or turbulent flows. I have heard claims that they can also handle two phase flows, but I remain very skeptical of the latter claim.
Doug

[Art Montemayor]

Coriolis flow meters have long been used very successfully on single-phase fluids at laminar or turbulent flow conditions.

However, bear in mind that liquids containing bubbles (air or gas) can cause dynamic changes to a Coriolis flow meter. These dynamic changes are not present in a single-phase fluid and they lead to significant measurement errors.

According to Micro-Motion, Inc. (a major supplier of Coriolis meters) Coriolis meters are not sensitive to flow profile and other disturbances that affect other metering technologies. For instance, since the fundamental measurement of delta T comes from the relative values of each of two tubes in bent-tube designs, swirl upstream of the meter doesn’t impact the measurement because it doesn’t mater how much flow goes through one tube or the other. Accuracy is not degraded even when one tube is completely plugged. A significant problem occurs with U-tube type meters that are subjected to flow rates too low to sweep bubbles out of the tubes. If the fluid velocity is less than approximately 0.6 m/sec, air will “hang up” in tube regions where the flow is against gravity. The solution is to keep flow rate high enough such that fluid velocity can purge the sensor of air. A rate of 20% of meter nominal flow (1 m/sec in the flow tube) or higher is adequate to completely purge the meter of bubbles and give good performance.

A significant problem with any 2-phase flow is found to occur at zero flow rate. When the flow is stopped, the multiple phases separate by gravity, prompting an imbalance in the tube. This imbalance causes an apparent meter zero change. Work on signal processing improvements to address this problem is currently a significant area of research.