Coriolis Mass Flow Meter is one of the few types of Flow Measurement and the most accurate type of flow measurement, before we discuss more deeply it’s good for readers to understand first from common things such as, definition, how to work, and the benefits of coriolis mass flow meter, let’s discuss
Definition of Coriolis Mass Flow Meter
Coriolis Mass Flow Meter is a type of flow meter that is mainly used in mass-related processes such as chemical reactions, heat transfer, etc. In all these processes, accurate flow measurement is a prerequisite.
There are many types of mass flow gauges available in the industry. However, the most widely used type is the Coriolis meter. Another type available is the thermal type mass flow meter.
The Coriolis gauge works on the Coriolis Effect, therefore so named. Coriolis meters are considered true mass gauges because they tend to measure the rate of flow mass directly while other flow metering technologies measure volumetric flow.
Also Read: Glass Tube Flow Meter: Definitions, Working Principles, and Applications
Since the mass does not change, no adjustment is required for the various characteristics of the fluid. Therefore, the Coriolis meter operates linearly. This type of meter is present in various designs.
The most common types of units of Coriolis mass flow meters:
- U-shaped flow tube
- sensor assembly
- electronic unit
In this meter unit, the liquid passes through a U-shaped tube that vibrates in angular harmonic oscillations. The Coriolis force will then damage the tube and the vibrational component is further added to the oscillating tube. This additional vibrational element results in phase shifts or rotations in some parts of the tube. A Coriolis meter is shown in the image below:
This resulting phase shift that is directly proportional to the rate of fluid mass flow is measured with the help of sensors. This measurable information is then transferred to an electronic unit where it is converted into a voltage proportional to the rate of mass flow.
Due to the construction properties of the coriolis mass flow meter sensor that is able to work at extreme temperatures of cold to heat and is able to work on high fluid pressures. Therefore, coriolis flow meters are very appropriate to be used by fluids that have expensive prices where less accurate accuracy can cause large losses both in terms of cost and quality of products.
Coriolis Flow Meter measures the mass of the fluid, not the volume so that if there is a liquid fluid flowing in the pipe that passes through the flow meter coriolis will be calculated mass so that if there is a mixture of air then the weight of air detected and calculated by the flow meter coriolis can be ignored mass.
Coriolis flow meters made from stainless steel are very suitable for use in various beverage and chemical industries because in addition to qualifying food grade requirements also have a fairly good resistance to the effects of liquids and corrosive environments.
How The Coriolis Mass Flow Meter Works
The coriolis meter has positive and negative coriolis acceleration into the measurement process, as illustrated in the image above where the fluid is flowed through two curved tubes. The excitation force of the oscillation is aimed at the tube through miniature velocity transducers or electric coils thus causing vibrations measured by magnetic sensors.
Coriolis flow meters vibrate at very small amplitudes, usually less than 0.1 inches (2.5 mm). This frequency is close to the device’s natural frequency, which is usually around 80 Hz. When there is no flow, the vibrating tube and the sine wave output of each hall-effect transducer is in phase. When the flow begins, the fluid flows through the tube thus inducing rotation or rotation to the tube due to the acceleration of the Coriolis Effect, which operates in opposite directions on either side of the given force.
For example, when the flow meter tube moves upwards during the first spin, the fluid flowing to the resists meter is forced up and presses the tube. Instead, the fluid flowing out of the resists meter with its vertical movement decreases thus pushing the tube. This action causes the flow meter tube to rotate. As it moves downwards during the two-round vibration cycle, the tube rotates in the opposite direction. This twisting results in a phase difference (time lag) between the inflow and outbound side, and this phase difference is directly affected by the mass passing through the tube.
Working Principles of Coriolis Mass Flow Meter
Note:
Note that the amplitude of vibration and rotation is very small compared to the size of a U-shaped tube. The graphic above is deliberately made redundant for illustrative purposes.
The effects of Coriolis on small parts of the liquid ∂ m are:
During rotation, the tube provides an upward retaining force for the fluid, or the fluid pushes the tube down. On the outlet side, the Coriolis style acts in the opposite direction.
For this problem, we assume that the tube has a perfect “U” shape, with a cross-sectional area of A. The length and width of each is l and d. The Coriolis effect, which acts in opposite directions on the sides of the in and out channel, produces a twisting moment, or Tc.
The K factor can be introduced to compensate for the more common “U” form, where Qm = ρAV is the flow rate.
The equations governing this spin are:
Where Iin the is the inertia of the U-shaped tube, Cin the is the attenuation coefficient, Kin the θ is the angle of spin, and t is time.
Knowing that the Coriolis flow meter vibrates in the shape of a U to produce rotation, the real angular velocity of Ω is the vibrating frequency function of ω.
Assuming that the term damping Cin the ignored, the equation twists into:
The specific solution (steady-statesolution) from the rotary angle is:
Furthermore, the angular velocity of the U-shaped tube is Ωl,and the displacement between these two angles is θ d/2. Therefore, the Ƭ time lag between the two corners is:
By measuring the time lag of Ƭ,the rate of mass flow can be obtained:
In vibration analysis, it is customary to use natural frequencies as a basis and normalize the term frequency against it. The natural frequencies of the U-shaped tube system are:
Note:
Note that Iin the includes the mass of the fluid in the tube.
then the mass flow meter becomes:
Until this development we already know and know more about the coriolis flow meter ranging from its understanding to the workings of the coriolis meter.
Also Read: Flow Meter Working Principles
Key Features of Coriolis Mass Flow Meter
- Coriolis gauges can be applied to a variety of applications ranging from adhesives and coatings to liquid nitrogen.
- The typical affordability of a Coriolis-designed curve tube varies from 100:1 to 200:1 while for straight tube meters the range is limited to about 30:1 to 50:1. In addition, the accuracy of the straight tube meter is low.
- In the case of Coriolis meters, no compensation is required for variations in temperature and pressure. Also mass measurements are insensitive to changes in viscosity and density.
- They are very helpful for handling fluids whose viscosity changes according to speed while temperature and pressure remain constant.
- These are called universal meters, because they are capable enough to measure almost any liquid, liquid and gas. They can measure all fluid flows such as Newtonian, non-Newtonian gases and are quite dense as well.
- They can be used to measure the density of liquids as well.
- There is no reynolds number limit combined with the Coriolis flow meter.
- They are also not affected by deformation in the speed profile.
Advantages of Using Coriolis Flow Meter
- Coriolis flow meters are able to measure a variety of fluids that often do not correspond to other flow measurement devices. The operation of the flow meter does not depend on the Reynolds number; Therefore, a very malignant liquid can also be measured. The Coriolis flow meter can measure the flow rate of Newtonian fluids, all types of non-Newtonian fluids, and porridge. Compressed gases and cryogenic liquids can also be measured by several designs.
- The Coriolis flow meter provides direct mass flow measurement without the addition of external measurement instruments. While the volumetric flow rate of a fluid will vary with changes in density, the rate of fluid mass flow does not depend on changes in density.
- The Coriolis flow meter has incredible accuracy. Basic accuracy is usually in the order of 0.2%. In addition, linear flow gauges across its flow range.
- The flow meter range is usually in the order of 20:1 or greater. The Coriolis flow meter has been successfully applied at a flow rate 100 times lower than its full-scale flow rate.
- The Coriolis flow meter is capable of measuring mass flow rate, volumetric flow rate, fluid density, and temperature—all from a single instrument.
- The operation of a flow meter is an independent flow characteristic such as turbulence and profile. Therefore, straight flow requirements upstream and downstream and flow conditioning are not required. They can also be used in installations that have a pulsating flow.
- Coriolis flow gauges do not have an internal barrier that can be damaged or clogged by slurry or other types of particles in the flow. Entrained gases or gas slugs in the liquid will not damage the flow meter. No moving parts, the witch will wear out in need of replacement. This design feature reduces the need for routine maintenance.
- Flow meters can be configured to measure flow in either forward or backward directions. In respectful flow there will still be a time or phase difference between the flow detectors, but the relative difference between the two detector signals will be reversed.
- Coriolis flow meter design is available, allowing for use in sanitary applications, and for measurement of shear sensitive fluids. Materials are available to allow measurement of corrosive liquids.
Disadvantages of Using Coriolis Mass Flow Meter
- Coriolis flow gauges are not available for large pipes. The largest Coriolis flow meter available today has a maximum flow rating of 25,000 lb/min (11,340 kg/min), and comes with a 6-inch (15 cm) flange. When a greater flow rate must be measured, two or more flow meters are required to be installed in parallel.
- Some flow meter designs require very high fluid speeds to achieve a large amount of time or phase differences between flow detector signals. This can result in a very high pressure drop in the flow meter.
- Coriolis flow gauges are expensive. However, the cost of a Coriolis meter is often comparable to (or below) the cost of a volumetric meter plus a densitometer used together to determine the rate of mass flow.
- The Coriolis flow gauge has difficulty measuring the rate of low-pressure gas flow. Applications with pressures of less than 150 psig are marginal with flow meter designs available today. Low-pressure gases have a low density, and their mass flow rate is usually very low. To produce enough mass flow rate to provide enough Coriolis force to be measured, the velocity of the gas must be very high. This in turn can lead to a very high drop in pressure on the meter.
Other Benefits of Coriolis Flow Meter
- Better accuracy than most other flow meter technologies.
- Can be used in a variety of liquid conditions (the list of liquids can be seen below)
- Able to measure the flow of hot liquids (example: Liquid sulfur) and cold (example: Liquid nitrogen)
- Decrease in low pressure
- Suitable for two-way flow
Also Read: Rheonik Mass Flow Meter
Thus the article about “Coriolis Mass Flow Meter: Definition, How It Works, and Benefits” hopefully can answer the questions that are in the minds of readers, hopefully useful.