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Flow Sensors- Electronic Device to Measure Accurate Flow Rate

Flow sensors, also known as flow meters, measure the flow of liquids or gases such as air passing through a pipe. The measurements help monitor industrial processes such as machinery operations to achieve efficiency and effectiveness on the performance. Flow sensors also help measure air intake in the engines and adjust the delivery of fuel on injectors to obtain a specific mixture of fuel required for an engine to operate. The medics also use flow sensors in getting the correct oxygen rate for patients who suffer from respiratory diseases.

Flow sensors work by using electrical and mechanical subsystems to measure fluids’ physical characteristics and calculate their flow. Various types of fluids behave when placed on the flow sensor. Therefore the type of the fluid will determine which flow sensor type to use. Mainly four types of flow sensors in demand that are used by each and every industry accordingly. which flow sensor type to use.

Advantages & Disadvantages of various Flow sensors like electromagnetic flow sensor, orifice flow sensor, turbine flow meter, Coriolis mass flow sensors, thermal mass flow sensors, variable area flowmeter, vortex flow sensors, etc. In this article, we are going to explain four types of flow sensors, In which explain their description, advantages, disadvantages, and applications.

Types of Flow Sensors

Types of flow sensors are generally classified into three main groups, namely;

1. Mass flow sensors
2. Positive displacement flow sensors
3. Velocity flow sensors
4. Differential Pressure Flow Sensors

Mass Flow Sensors

Mass flow sensors, also known as mass airflow sensors, measure the mass flow of air getting into the air intake system in an internal combustion engine. It also determines the amount of fuel an engine should have to enhance ignition through a fuel-air mixture.
One can also use a mass flow sensor to measure the energy transfer from a heated surface to the fluid flowing in the pipe. The two types of mass flow sensors include hot wire and the vane meter, commonly used in the automotive industry.

Applications of mass flow sensors

Mass flow sensors are essential in injecting fuel on the engines and ensures efficiency in the combustion process in the automotive industry. It also supplies the information on the onboarding computers that brings about the proper levels of fuel injection.

Used in the Automotive industry

Used in medical applications

Mass flow sensors help deliver ventilators or anesthesia by performing on the same concept of heat loss in automotive. It also monitors the gas flow rates required in mitigating the risk of patients who have respiratory complications by providing a quick response time for the doctor to do what is required.

Used in leak testing

Mass airflow sensors help detect leaks in pipes and feature the magnitude of the leak. Therefore it is suitable to measure hazardous and flammable gases to provide a quick and efficient response to any leak.

Used in analytical industries

Mass flow sensors help identify unknown compounds in gas chromatography by tracing the information about flow rate on the separation columns and the injection process in the machine.

Advantages

i)Mass flow sensors help in robust measurements like in automotive industries.
ii) They have got a variety of design options.
iii) Mass flow sensors have no moving parts; hence easy to handle and maintain.

Disadvantages

i)Some mass flow sensors like thermal require calibration.
ii) They have got less intake of air.
iii) The sensor may fail to function due to contamination.

Positive Displacement flow sensors

Positive displacement flow sensors are the only flow sensors that provide a direct measurement of fluid volume moving through the pipe using the rotating parts to pass the known volume of the fluid before allowing another fluid amount to pass through the device. The rotational velocity is always directly proportional to the flow rate.

Examples of positive displacement flow sensors include vane, oval gear, rotor, oscillating piston, multi-piston, and nutating disk.

Applications

i)Used in the water and wastewater industry.
ii) Used in the oil and gas industry.
iii) Used in the food and beverage industry.
iv) Used in pulp, paper, and chemical industry.
v) Used in the pharmaceutical industry.

Advantages

i)They have a long life and low maintenance costs.
ii) They can work on dirty and viscous liquids.
iii) There is a direct readout of measurement.
iv) They have good accuracy and provide repeatability.

Disadvantages

i)They are expensive and more difficult, especially in large pipe diameters.
ii) Sudden flow change, which causes inactivity, may damage the moving parts.
iii) They are restricted to fluids with high viscosity.

Velocity Flow Sensors

Velocity flow sensors work by holding the fluid’s velocity through the sensor to get the flow rate. Examples include electromagnetic and mechanical (propeller and turbine) flow sensors.

Applications

Velocity flow sensors are generally used in aircraft to determine the speed of air by measuring vapors and air in different industrial applications such as useless water treatments. They do this using a pitot device which turns the kinetic energy into potential flow energy.

Advantages

i) A Velocity flow meter such as mechanical use less energy but are always short and co-effective in their operations.
ii) They can check measurements under low/high temperatures and pressure.
iii) They can measure flows of liquid with a contamination degree without pressure drops in the channels.

Disadvantages

i) The moving parts of the flow meter can be subjected to wear and tear.
ii) High/Low maintenance costs.
iii) Some of the flow sensors do not work with non-conductive liquids, e.g., electromagnetic.

Differential Pressure Flow Sensors

A fluid’s velocity is directly related to the fluid’s pressure.
Differential pressure flow sensors measure the pressure of the fluid. This flow sensor measures pressure at two different velocities while maintaining fluid density. For all types of differential pressure flow sensors, a single pressure sensing node is required ― like a pitot tube ― sits on the end of the path of the channel. A nozzle in orifice diameter stimulates the liquid, which is measured again at a higher speed. Once the differential flow sensor defines the difference in pressure, In this situation, we can apply the Bernoulli equation to find the liquid velocity. Finally, we can use that liquid velocity to determine the overall flow rate through the channel.

All these flow sensors have different degrees of efficiency and system pressure loss. Differential pressure flow sensors are the most simple and popular type of flow sensors due to their appearance and versatility.

Advantages:

  • Universally suitable for fluids, gases, and steam.
  • Also available in extreme situations, e.g., viscosity, due to a variety of versions
  • Computations are possible in extreme situations.
  • It is a perfect flow sensor device that is suitable for excessive temperatures and pressures
  • Range varies possible.
  • Low-pressure drop for nozzles gives an accurate result.

Limitations:

Smaller span due to square root relation between flow rate and differential pressure|
Damaged by Density and pressure changes
Inlet and outlet section is covered a large area.
Costly installation and its fitting
Costly Maintenance
Edge sharpness for orifice plates must be ensured, therefore no solids or contamination

Conclusion

Flow sensors have helped in enhancing the technological environment for multiple applications in many industries. The flow sensors can manage the flow rate even at low/high temperatures and pressures, always a pro. These flow sensors devices are useful for both domestic and industrial purposes.

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