The Coriolis Effect

By Uche Umekwe

What Is The Coriolis Effect?The Coriolis effect is named after

Gustave-Gaspard Coriolis, a French mathematician and engineer who first described the phenomena.

The Coriolis Effect can be defined as an apparent deflection of moving objects when they are viewed from a rotating frame of reference.

Coriolis Effect In Practice

Example A – Merry Go Round, thrown ball.

(A) (B) (C)

(Dot Physics, 2015)

Coriolis Effect In Practice

Example B – Merry Go Round, water jet.

(A)(B)

(C)

Fixed tube along radius

Coriolis Flow MeterA Coriolis mass flow meter

works on the principle of measuring the mass of a fluid using the Coriolis Effect.

This is achieved by subjecting a fluid flowing in a pipe to Coriolis acceleration.

Although it is not possible for a meter to rotate (yet) a rotating frame reference can be produced via oscillation or by inducing vibration in a tube.

 

(www3.emersonprocess.com, 2015)

How A Coriolis Flow Meter Works

Fluid flow away from the axis of rotation results in a force to maintain angular momentum.

When fluid is moving through the tubes, Coriolis forces are induced causing the flow tubes to twist in opposition to each other.

How A Coriolis Flow Meter Works

At rest (no flow) there is no Coriolis effect and the uniform vibration of the tubes create a symmetrical waveform.

The twisting effect due to Coriolis forces causes a “phase shift” between the previously symmetrical waveform.

The time difference between the sine waves is measured (ΔT) and is directly proportional to the mass flow rate.

Practical Flow Metering ApplicationsBenefits

Multivariable Measurements

Can be used to measure various parameters including:-

Mass Flow.Volumetric Flow. Density.Temperature.% Solids.

Measures flow at different single phases i.e. liquids, Gases and Slurries.

Practical Flow Metering ApplicationsBenefits

Easy to Install and Maintain

Can be applied to all flow patterns.

No moving parts therefore less wear and tear expected.

Measures reverse flow as well as forward.

Practical Flow Metering ApplicationsBenefits

High AccuracyMicro Motion 2-Wire Coriolis Flow and Density Meter specifications:

+/- 0.15% of rate Liquid Mass Flow.+/- 0.10% of rate Liquid Volume Flow.+/- 0.35% of rate Gas Flow.

Practical Flow Metering ApplicationsLimitations

Entrained Gas

Lower accuracy for two phase flow.

Entrained gas causes decoupling effects which is high at low viscosity.

Pattern (2005)

Practical Flow Metering ApplicationsLimitations

Flashing

Unable to use in flashing applications e.g. flash separation.

Flashing within the flow meter can cause the tubes to become out of balance.

Practical Flow Metering ApplicationsLimitations

Sensitivity

Sensitive to vibration close to operating frequency.

Sensitive to pulsations close to operating frequency.

Potential erosion due to abrasive particles.

Any Questions?ReferencesChipkin.com, (2015). Coriolis Mass Flowmeters | Chipkin Automation Systems. [online] Available at: http://www.chipkin.com/mass-flowmeters/ [Accessed 1 Apr. 2015].

Dot Physics, (2015). RP 10: Centripetal Force, Centrifugal Force – what’s the deal?. [online] Available at: http://scienceblogs.com/dotphysics/2009/12/31/rp-10-centripetal-force-centri/ [Accessed 1 Apr. 2015].

Pattern, T. (2005). Keep metering problems from bubbling up. Chemical Processing. [online] Available at: http://www.chemicalprocessing.com/articles/2005/583/ [Accessed 31 Mar. 2015].

(Micro Motion TUTOR - Coriolis Flow Measurement Technology Tutorial. [online] Available at: http://www3.emersonprocess.com/micromotion/tutor/28_flowoprinccurvtubevib.html [Accessed 1 Apr. 2015].

OMEGA Complete Flow and Level Measurement Handbook and Encyclopaedia, OMEGA Press, 1995.