An Overview of Gas Flow Measurement - Chemical Engineering

13 May.,2024

 

An Overview of Gas Flow Measurement - Chemical Engineering

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Gas-measurement technologies

There are two basic types of flowmeters: liquid and gas. Liquid is primarily measured in terms of volumetric flowrate, while gas is a mass-flow measurement because of the unique properties of gases when compared to liquids. While some volumetric technologies can measure gas flowrates, there can be problems with totalized flow. Generally, the best choice is mass-flow sensing technology when measuring air or other gases — especially in critical applications.

Coriolis. The principle of operation for Coriolis flowmeters relies on a vibrating tube where the flow of fluid causes changes in frequency, phase shift or amplitude, which is proportional to the mass flowrate. Coriolis meters are highly accurate and are frequently used in custody transfer applications, but they are on the expensive side and require labor-intensive inline applications.

Differential pressure. Differential pressure (DP) meters and sensors come in several designs, including orifice plates, pitot tubes and Venturis. The typical DP meter designs require the fluid to move through or past two points of reference, creating a differential pressure rate that is equivalent to the rate of flow using the Bernoulli equation with some modifications. If the gas is dirty, there can be orifice clogging issues that require frequent maintenance in order to maintain accuracy.

Ultrasonic. Flowmeters designed with ultrasonic flow-sensing technology rely on ultrasound and the Doppler effect to measure volumetric flowrate. In ultrasonic flowmeters, a transducer emits a beam of ultrasound to a receiving transducer. The transmitted frequency of the beam is altered linearly by particles or bubbles in the fluid stream. The shift in frequencies between the transmitter and receiver can be used to generate a signal proportional to the flowrate.

Optical. Flowmeters designed with optical sensing rely on laser technology and photo detectors. This technology requires the presence of particles in the gas stream. These particles scatter the light beam, and the time it takes for these particles to travel from one laser beam to the other laser beam can be used to calculate the gas velocity and volumetric flowrate. These meters have good accuracy and wide turndown, but are traditionally expensive.

Thermal dispersion. Flowmeters with thermal-dispersion sensors provide direct mass-flow measurement. Two thermowell-protected platinum resistance temperature detector (RTD) sensors are placed in the process stream. One RTD is heated while the other senses the actual process temperature. The temperature difference between these sensors generates a voltage output, which is proportional to the media cooling effect. This information can be used to measure the gas mass flowrate without the need for additional pressure or temperature transmitters.

In measuring flow accurately, second only to selecting the proper flow sensing technique is the method of calibration. There are two methods used in calibrating gas flowmeters, as follows:The direct method, where the meter is calibrated to a specific pure process gas or to the actual components of a mixed gas in use.

The air equivalency method, where the meter is calibrated using air, and then the calibration is adjusted with a pre-defined correction factor.

It is important to ask your supplier about the method of flowmeter calibration. Users should know if manufacturers contract out for calibration and if so, with whom, or if they operate their own calibration laboratory with direct-method calibration test stands and equipment that is traceable in accordance with NIST and ISO/IEC 17025 standards.

How to Measure Flow Rate of Gases with a Digital Flow ...

Exploring Use Cases and the Benefits of Oxygen and CO2 Digital Mass Flow Meters from Kelly Pneumatics

Introduction:

The accurate measurement of gas flow rates is essential for numerous industrial and scientific applications. One of the most reliable and precise methods for measuring gas flow is through the use of a digital mass flow meter. In this blog post, we’ll discuss how digital flow meters work, several use cases for these devices, and explore the utility of the Oxygen and CO2 Digital Mass Flow Meters available from Kelly Pneumatics. We will also provide an overview of these products, explaining their functionality and potential use cases.

Understanding Digital Mass Flow Meters:

A digital mass flow meter is a device that measures the mass flow rate of gases in real-time. Unlike volumetric flow meters, mass flow meters are unaffected by changes in temperature or pressure, ensuring accurate and consistent measurements. Digital flow meters utilize various technologies, such as thermal sensing or Coriolis effect, to measure the flow rate of gases. These devices offer a range of benefits, including high precision, fast response times, and compatibility with numerous gas types.

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Use Cases for Digital Mass Flow Meters:

Gas Delivery Systems: In industries that require precise gas mixtures, such as semiconductor manufacturing, digital mass flow meters ensure accurate gas flow rates and help maintain the desired gas concentration.

Environmental Monitoring: Monitoring and controlling greenhouse gas emissions and air pollution levels require precise measurement of gas flow rates. Digital mass flow meters can measure various gases, including CO2 and oxygen, to track and regulate emissions.Medical Applications: Accurate gas flow measurements are critical in medical applications, such as respiratory therapy, anesthesia delivery, and oxygen therapy. Digital mass flow meters ensure the delivery of the correct gas concentrations for patient safety and treatment effectiveness.

Laboratory Experiments: In research and development settings, digital mass flow meters are essential for accurately controlling and measuring gas flow rates during experiments, ensuring consistent and reliable results.Industrial Process Control: Many industrial processes, such as chemical synthesis or combustion, require precise control of gas flow rates to maintain optimal conditions and ensure product quality.

The brewing and fermentation industry is another area where precise CO2 and oxygen flow measurement is crucial. During fermentation, yeast consumes sugar and produces CO2 and alcohol as byproducts. Monitoring and controlling the CO2 levels within fermentation tanks is essential for maintaining optimal yeast performance and ensuring the desired taste and quality of the final product. Similarly, oxygen flow control is critical in the initial stages of fermentation, as it promotes yeast growth and improves fermentation efficiency. Using digital mass flow meters for CO2 and oxygen in these applications ensures precise control over gas levels, resulting in consistent and high-quality outcomes.

Aquaculture is another industry where accurate CO2 and oxygen flow measurement plays a significant role. In fish farms and other aquatic environments, maintaining appropriate oxygen and CO2 levels is crucial for the health and well-being of the organisms. Oxygen flow measurement helps ensure that the aquatic species receive adequate oxygen levels, which is especially important in high-density fish farming systems where oxygen can be depleted rapidly. Simultaneously, monitoring and controlling CO2 levels is essential, as high concentrations of CO2 can cause stress and negatively impact the growth and health of aquatic organisms. By employing digital mass flow meters for oxygen and CO2, aquaculture facilities can maintain ideal conditions for their aquatic species, resulting in improved productivity and healthier organisms.

Oxygen and CO2 Digital Mass Flow Meters from Kelly Pneumatics:

Kelly Pneumatics, a renowned provider of high-quality pneumatic products, offers advanced digital mass flow meters designed for measuring oxygen and CO2 flow rates. These devices are designed to deliver accurate, reliable, and consistent measurements for various applications.

The Oxygen and CO2 Digital Mass Flow Meters from Kelly Pneumatics utilize thermal sensing technology to measure gas flow rates. These meters offer a fast response time and a wide flow rate measurement range, making them suitable for numerous applications. The digital mass flow meters are designed to be user-friendly, with an easy-to-read display and straightforward installation.

Functionality:

These digital mass flow meters measure the flow rate of gases based on the principle of heat transfer. A heated sensor element is placed in the gas flow path, and as the gas flows over the sensor, it causes heat to be transferred from the sensor to the gas. The flow rate of the gas can be determined by measuring the temperature difference between the heated sensor and a reference temperature sensor.

Potential Use Cases:

The brewing and fermentation industry is another area where precise CO2 and oxygen flow measurement is crucial. During fermentation, yeast consumes sugar and produces CO2 and alcohol as byproducts. Monitoring and controlling the CO2 levels within fermentation tanks is essential for maintaining optimal yeast performance and ensuring the desired taste and quality of the final product. Similarly, oxygen flow control is critical in the initial stages of fermentation, as it promotes yeast growth and improves fermentation efficiency. Using digital mass flow meters for CO2 and oxygen in these applications ensures precise control over gas levels, resulting in consistent and high-quality outcomes.

Aquaculture is another industry where accurate CO2 and oxygen flow measurement plays a significant role. In fish farms and other aquatic environments, maintaining appropriate oxygen and CO2 levels is crucial for the health and well-being of the organisms. Oxygen flow measurement helps ensure that the aquatic species receive adequate oxygen levels, which is especially important in high-density fish farming systems where oxygen can be depleted rapidly. Simultaneously, monitoring and controlling CO2 levels is essential, as high concentrations of CO2 can cause stress and negatively impact the growth and health of aquatic organisms. By employing digital mass flow meters for oxygen and CO2, aquaculture facilities can maintain ideal conditions for their aquatic species, resulting in improved productivity and healthier organisms.

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