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Thermal gas mass flow meter law and working principle
- 2019-06-03-

First, the thermal gas mass flow meter has the following technical advantages:

♦ True thermal gas mass flow meter, which does not require temperature and pressure compensation for gas flow measurement, and the measurement is convenient and accurate. A mass flow rate of the gas or a standard volume flow rate can be obtained.

♦ Wide range ratio, which can measure gas flow rate up to 100Nm/s bottom to 0.5Nm/s, which can be used for gas leak detection.

♦ Good seismic performance and long service life. The sensor has no moving parts and pressure sensing parts and is immune to the influence of vibration on the measurement accuracy.

♦ Easy to install and maintain. Non-stop production installation and maintenance can be achieved where field conditions permit.

♦ Digital design. The overall digital circuit measurement, accurate measurement and convenient maintenance.

♦ RS-485 communication, or HART communication, can realize factory automation and integration.

Second, the thermal gas mass flow meter is a meter that measures the flow using the principle of heat conduction.

The meter uses the constant temperature difference method to accurately measure the gas mass flow. The utility model has the advantages of small volume, high digitization degree, convenient installation and accurate measurement. The sensor consists of two reference-level thermal resistors (RTDs). A bridge loop is used, one is the speed sensor RH and the other is a temperature sensor RMG that measures the temperature change of the gas. When the two RTDs are placed in the gas to be measured, where the sensor RH is heated, the other sensor RMG is used to sense the temperature of the measured gas. As the gas flow rate increases, the gas stream carries more heat and the temperature of the sensor RH drops. The meter can measure flow under high temperature and high pressure conditions.

The thermal gas mass flowmeter has a determined mathematical relationship between the heating power P, the temperature difference ΔT (TRH-TRMG) and the mass flow rate Q according to the law of heating. P / ΔT = K1 + K2 f (Q) K3 K1, K2, K3 are constants related to the physical properties of the gas. The unique temperature difference measurement method of ZN series thermal gas mass flowmeter overcomes the large zero drift caused by water, oil and impurities in the gas when measuring the gas flow rate by the thermal gas mass flowmeter using the principle of constant temperature difference. The drawbacks of measurement. It can also be used to measure the mass flow of wet gases, such as real-time detection of gas volume (speed) in underground gas drainage, air supply, and exhaust systems.

Thermal gas mass flow meters are divided into: plug-in type and pipe type according to the installation method. Plug-in sensors are available for online installation and online maintenance. The installation process is to first weld the base with external thread on the outer wall of the pipe, install a 1-inch stainless steel ball valve on the base, and then use a special tool to make the pipe a hole with a diameter of 22mm. After punching, remove the special tool and finally the sensor. Installed on the valve and inserted into the center of the tube (the insertion position of the sensor is determined at the factory). Plug-in sensor for pipe diameter: DN80 ~ 6000mm (larger pipe diameter when ordering).

Third, the working principle of the thermal gas mass flowmeter:

The thermal gas mass flowmeter adopts the principle of thermal diffusion. The thermal diffusion technology is a technology with excellent performance and high reliability under severe conditions. The typical sensing element includes two thermal resistors (platinum RTD) and one is a speed sensor. One is a temperature sensor that automatically compensates for changes in gas temperature. When the two RTDs are placed in the medium, the speed sensor is heated to a constant temperature difference above ambient temperature and the other temperature sensor is used to sense the medium temperature. The mass flow of gas through the velocity sensor is calculated by the amount of heat transfer from the sensing element. As the gas rate increases, the amount of heat that the sensor delivers to the medium increases.

All products are designed with no moving parts and are not blocked by dirty media or media particles.

Wide range ratio of 100:1, sensitive to low flow, no multi-level measurement, suitable for various ranges on site.

There is almost no pressure loss, which overcomes the drawbacks of the traditional differential pressure method that cannot be measured due to low pipeline pressure.

Solve various practical problems of the user (such as the installation of straight pipe segments are not satisfied, the components change, the measurement results are not good, etc.). The component changes can be corrected, the sensor can be cleaned online, and the insertion length can be adjusted freely.

The sensor can be single/multiple to meet various requirements and high precision measurement.

Sensor plug-in or in-line mounting reduces installation costs and is suitable for a variety of pipe diameter measurements.

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Company Address:North Section of Yuanxin Road, Xinxiang City, Henan Province

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