Measuring Gas Flow — Different Sensor Types
Across various industrial applications, medical devices, and aerospace processes, different gases are being compressed due to excessive heat or sudden cold. When they are placed under pressure, some potential negative outcomes regarding safety, maintenance, production consistency, and efficiency might arise. In order to accurately measure gas flow and maintain the rates of gases at a sufficient and functional level, various industries use gas flow meters.
Βut, what is a flow meter and where it can be used?
The purpose of a flow meter is to measure, as precisely as it could, the rate that a constant gas flows in a pipe. The measured and accurate result could make it possible that any operation would function safely and with compliance with the environmental laws.
Examples
How does a flow sensor work?
Well, we mainly use the Combined Gas Law along with three gas laws; Boyle’s Law, Charles’ Law, and Gay-Lussac’s Law.
PV/T = k
with “P” being the pressure, “V” the volume, “T” the temperature, and “k” a constant
When the combined gas law is used along with Avogadro’s law, it results in the ideal gas law. The combined gas law has no owner or discoverer. The above law combination can also be provided with the following formula:
P1V1/T1 = P2V2/T2
- Further Reading: An Overview of Gas Flow Measurement
Difficulties & challenges in gas flow measurement
Not every operation is feasible, as many challenges may arise. That is why you have to keep in mind any measurement you might face and requires your attention like:
- Need for straight — run operation: Some straight-run requirements may not be available in crowded production sites and process plants, so they should be considered.
- Durability to hazards: High flow conditions of many gases may damage flow meters/sensors during upset conditions.
- Exact calibration to any process: Since many gas turbine and compressor applications require flow meter calibrations, the gas flow meter is essential for undisturbed operations.
- Compatibility to the size: You should consider the suitability of the size for each implement, either small or large that could fit proportionally.
- Applicability to low and high flows: Any gas flow measurement should provide precise results at any flow level.
Different types of gas flow sensors
Considering the fact that there are more than one technologies and application a gas flow meter can be incorporated, you can find at least 8 measurement technologies. Each one has its pros and cons and great attention should be given when you choose the one for you. It could save you from extra costs and most importantly losing time.
1. Thermal Dispersion Flow Sensor
Thermal flowmeters are common meters that use heat to measure the flow rate of a fluid. In the middle of its structure, there is a heating element with other two temperature sensors, one on its right and one on its left side. While the gas starts to flow, heat is transferred and measured by the two sensors. Due to that, it can provide accurate and reliable results.
Applications Some of their typical applications include measurement and totalization of compressed air or gases and greenhouse gas emissions.
2. Paddle Wheel Type
As its name indicates, paddlewheel flowmeters use the mechanical energy of the fluid to rotate a paddle wheel in the flow stream. When the fluid moves faster, the paddlewheel spins proportionally faster and can be sensed mechanically, and transmits a pulse signal.
Applications: In applications like fume scrubbers, reverse osmosis and in various other fields, paddlewheel flow meters can be of great use.
3. Coriolis Mass Flow Meter
The main working principle of Coriolis flowmeters is the use of a vibrating tube where the flow of gas can cause changes in frequency, or phase shift proportional to the mass flow rate.
Applications: Different industrial sectors where the measurement of sanitary and relative clean gases is needed.
4. Electromagnetic Flow Meters
With an electromagnetic coil that can be found within those meters, a magnetic field is generated, along with electrodes that detect and measure the gas flow by using Faraday’s Law of induction.
Applications: In various industries, like food industries, chemical applications, natural gas supplies, and power utilities as they are not affected by diversities in pressure, density, and temperature.
5. Vortex Type Flow Meter
The technology used in vortex gas flow meters is a column-shaped shedder that obstructs the flow path and keeps it around while it generates vortices proportional to each other. This way, the number of vortices makes it possible to measure flow.
Applications: Systems like in power generation and heat-supply regarding compressed air, saturated steam, or at high temperatures, etc.
6. Floating Element Type
In order to use this instrument, you have to understand its method. It usually involves float in a tapered pipe. As the fluid is forced to pass in between the tapered pipe and the float, we get a differential pressure, and the float moves.
Applications: Various applications such as chemicals, compressed air, gases, etc.
7. Ultrasonic Flow Meter Type
Ultrasonic flow sensors usually measure the volumetric flow rates of a wide variety of gases relying on ultrasound and the Doppler Effect. This technology is extremely accurate and is independent of pressure, temperature, and viscosity.
Applications: Ultrasonic flow sensors have many applications, spanning from process flow to custody flow.
8. Differential Pressure Flow Meter
Differential pressure sensors can provide flow measurements through piezoresistive pressure sensors with welded metallic membrane using Bernoulli’s equation. For instance, on the occasion that the pressure might log high flow rate results, might be because of the high-pressure drop.
Further Reading: What’s piezoresistive pressure technology?
Applications: Many industries, such as power supply, food and beverage, medical, aerospace, and HVAC are quite compatible.
Before making your choice
Keep in mind the location of the manufacturer’s installation requirements before your final decision about the gas flow meter you want. Along with the prerequisites, you should never forget the maintenance that each technology may need and the costs to make it possible.
Please view the original article, along with diagrams and more information about gas flow measurement at https://esenssys.com/gas-flow-meter-types/.
