What is a Thermal Mass Flow Meter?
Thermal mass flow meter is a direct mass flow meter mainly used to measure gas mass flow. When the gas is heated on the surface, it can measure the heat transfer to work. The amount of heat transfer is directly proportional to the amount of gas molecules connected to the heating surface. This means that flow measurement has nothing to do with the temperature and pressure of the gas.
In many research and production processes, the important variable is mass rather than volume. Volumetric flow measurement is not as reliable as mass flow measurement because of the effect of temperature or pressure changes on the density of a fixed volume of gas.
Since its introduction in the mid-1970s, the instrument has undergone considerable development, from analog to digital, from small flows to large flows, from laboratory and equipment applications to industrial environments and even hazardous area applications. There is a suitable thermal mass flow meter for almost all gas applications.
Working Principle of the Thermal Mass Flow Meter
The working principle of a thermal mass flow meter adopts the theory of heat decentralization. Under this theory, the heat absorbed by the fluid in the pipeline is directly proportional to its quality flow. In a typical thermal flow meter, the gas flowing through the heat will absorb heat and cool the source.
- Heat Transfer
As the gas flows through the heating element, heat is transferred from the heating element to the gas. - Temperature Difference
The rate of heat loss is proportional to the mass flow rate of the gas. - Measurement
By measuring the temperature difference between the heating element and the gas, the flow rate can be determined.
In the measuring section where the gas passes, there are two thermal resistors, one of which is used for temperature detection and the other as a heater. The temperature sensing element detects the gas temperature, and the heater maintains a constant temperature difference between its temperature and the temperature of the measured gas by changing the current.
When the gas flow rate increases, the cooling effect is greater, and the current required to maintain a constant temperature between the thermal resistors is also greater. This heat transfer is proportional to the gas mass flow rate, that is, the supply current and the gas mass flow rate have a corresponding functional relationship to reflect the gas flow rate.
Read more about: Thermal mass flow meter calculation formula.
Benefits of Thermal Mass Flow Meter
Thermal mass flow meters offer many advantages including direct mass flow measurement without the need for pressure or temperature correction, high sensitivity at low flows, high turn-down ratios, easy installation, low-pressure drop, no moving parts, high reliability, and cost-effectiveness for a wide range of gas applications.
- Application Flexibility: Thermal mass meters are suitable for a wide range of applications, whether you are looking for specific gas measurements or require a thermal air flow meter.
- Wide Rane Ratio: Can measure gas flow rate as high as 100Nms and as low as 0.5Nm/s, can be used for gas leak detection.
- No Moving Parts: Thermal flow meters are easier and less expensive to maintain than flow meters with moving parts.
- High Sensitivity at Low Flows: They can accurately measure very low flow rates, making them ideal for applications that require precise monitoring of small amounts of gas.
- Very Low Pressure Drop: Thermal mass flow meters have negligible pressure drop, making them a top choice for a wide range of pipe and duct sizes.
Application of Thermal Mass Flow Meter
Thermal mass flow meters are used for direct mass measurement of industrial gases. In gas metering applications in any industry, high turndown ratios or low-pressure losses are important. Thermal mass flow meters can offer a real alternative to traditional measurement technologies.
The thermal measurement principle is widely used in industry and has been successfully applied to many gas flow applications including:
- Oxygen, nitrogen, hydrogen, chlorine, natural gas, liquefied gas, flare gas, compressed air, and multi-component gas measurement.
Aeration and krypton gas measurement in biogas and water treatment. - Gas flow in cement, cigarette, and glass factory production process, carbon dioxide gas flow in the beer production process, gas flow in semiconductor chip production process, and gas flow in the solvent recovery system.
- Blast furnace gas, coke oven gas, flue gas, air in gas process, calciner flue gas, and combustion gas in coal-fired boilers.
- Flue gas flow (speed) measurement of chimney exhaust (CEMS).
- Primary air, secondary air, ventilation or exhaust system flow in mines, and gas flow (speed) measurement in heating, ventilation, and air conditioning systems of power plant blast furnaces.
Featured Types
A thermal gas mass flow meter measures gas flow using the principle of thermal diffusion. Sino-Inst’s thermal gas mass flow meters are available in insertion and inline pipe section types.
Insertion Thermal Mass Flow Meter for Large Pipes
Insertion Thermal Mass Flow Meter is suitable for flow measurement of large diameter gas pipelines. Easy to install and economical to use. Pipe range: diameter above DN65.
- True mass flow meter. No temperature or pressure compensation is required for gas flow measurement. The mass flow rate or standard volume flow rate of the gas can be obtained;
- The measuring range ratio is wide (greater than 100:1), easy to load and unload, and easy to use;
- Measuring medium: various gases (except acetylene gas);
- Pipe range: diameter above DN65;
- Supply type: integrated structure, split structure;
- Display content: temperature, instantaneous flow, cumulative flow;
- Power supply: 24V power supply or 220V power supply;
- Output: 4～20mA, 485 communication;
Pipe Type Thermal Gas Mass Flow Meter
- Real mass flow meter. There is no need for temperature and pressure compensation for gas flow measurement, and the measurement is convenient and accurate. The mass flow rate or standard volume flow rate of the gas can be obtained.
- Wide range ratio, capable of measuring gases with flow rates as high as 100Nm/s and as low as 0.5Nm/s. Can be used for gas leak detection.
- Good seismic resistance and long service life. The sensor has no moving parts and pressure sensing parts and is not affected by vibration on measurement accuracy.
- Easy to install and maintain. If site conditions permit, non-stop installation and maintenance can be achieved. (Special customization required).
- Digital design. Overall digital circuit measurement, accurate measurement, and easy maintenance.
- Using RS485 communication or HART communication, factory automation and integration can be realized.
- The power supply is optional AC220V, DC24V or AC220VDC24V dual power supply.
Thermal Mass Flow Meter-Controller
There is also a type of thermal mass flow meter that is specifically used to measure small gas flows. In addition, this type of thermal mass flow meter can also add flow control functions.
How to Choose a Thermal Flow Meter According to the Price?
When choosing a thermal mass flow meter, it is important to first understand the requirements of your application and select a meter that matches your needs.
- Accuracy Level:
Evaluate how much accuracy your application really needs. If high accuracy is not critical, a meter with slightly less accuracy but a lower price may be a better fit. - Flow Range:
Consider the range of flows you need to measure. Meters designed for a wider flow range may be more expensive than those with a narrower range. - Fluid Type:
Different fluids may require specialized sensors, which can affect price. - Temperature and pressure:
High-temperature and high-pressure thermal mass flow meters generally need to be customized separately. The cost will be relatively high. - Features and Functionality:
Advanced features such as data logging, communication protocols, or built-in diagnostics may increase costs. - Brand and Reputation:
Reputable manufacturers may have higher prices due to quality control and technical support. - Compare Quotes from Multiple Suppliers:
Get price comparisons from different manufacturers to find the best product for your needs.
Thermal gas mass flow meters directly measure and display the mass flow rate or normalized volume flow rate of gas without any additional pressure and temperature compensation. Support 4-20mA, pulse signal output, RS485 communication, or HART communication to achieve factory automation measurement and control.
Sino-Inst has a variety of thermal mass flow meters to choose from. Our thermal gas mass flow meter can measure various gases (unstable media such as acetylene and boron trichloride cannot be measured). It is helpful for industrial gas flow management and department consumption allocation, experiments, and research. If you need to purchase a gas mass flow meter, please feel free to contact our sales engineer!
