Basic principle

The thermal mass flow meter measures the mass flow of the fluid by measuring the temperature field change when the fluid flows through the pipe heated by the external heat source, or by using the relationship between the energy required for the fluid temperature to rise and the mass of the fluid when the fluid is heated. This flow meter is mainly used to measure the mass flow of gas, and has the characteristics of high accuracy, high repeatability and high reliability.

 

Specific implementation method

Constant temperature difference method:

Sensor structure: The sensor part in the thermal mass flow meter usually consists of two reference-level thermal resistors (such as platinum resistance temperature sensor), one as a heater (speed sensor) and the other as a temperature sensor. The two thermal resistors are placed in the pipeline to measure the temperature and flow rate of the fluid.

 

Working principle: When working, the heater is heated to a temperature higher than the fluid temperature (T2), and the temperature sensor measures the temperature of the fluid (T1). The difference between the two temperatures ΔT (T2-T1) is maintained at a constant level. When the fluid flows through the pipeline, it takes away some of the heat from the heater, causing T2 to drop. In order to keep ΔT constant, the control system increases the power supply current of the heater to compensate for the heat taken away by the fluid. The faster the fluid flows, the more heat is taken away, so the more current needs to be added. This increase in current is proportional to the mass flow rate of the fluid, thus achieving the measurement of the fluid flow rate.

 

Energy balance method:

Another way to achieve this is to calculate the mass flow rate of the fluid by measuring the energy required to raise the temperature of the fluid by a certain value. However, this method is not common in thermal mass flow meters, and is more used in theoretical analysis and research.

 

Advantages and applications

Advantages: Thermal mass flow meters have the advantages of low pressure loss, large flow range, high accuracy, high repeatability and high reliability. At the same time, it has no moving parts, so it has a long service life and low maintenance costs. In addition, it can also be used for monitoring and control of extremely low gas flows.

Application: Thermal mass flow meters are widely used in many industrial fields, such as coal gas flow measurement in steel plants and coking plants; boiler air flow measurement; and fluid flow measurement in chemical, petroleum, pharmaceutical, food and other industries. In these fields, thermal mass flow meters can provide accurate and reliable flow data, providing strong support for the control and optimization of production processes.

 

Precautions

When using a thermal mass flow meter, the following points should be noted to ensure the accuracy of the measurement results:

 

Make sure that the connecting bolts of the pipeline are tightened and there is no leakage at the connection.

The applied pressure cannot be greater than the maximum working pressure specified by the flow meter.

When measuring harmful gases, pay attention to protective measures to avoid inhaling the gas.

When plug-in installation connection, the connection should be sealed with sealant to prevent leakage.

When inserting and removing the flow meter, make sure that the two probes do not touch the pipe wall or ball valve to avoid damaging the flow meter.

 

If you want to know the specific selection and quotation of thermal mass flow meter, please consult CIXIFM winny:

Email:sales01@cxflowmeter.com

whatsapp:008618049841995