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Mass Flow Controller Introduction - Focus on Microfluidic Control Technology

Mass flow controller, the principle is as follows:
“Two pairs of heaters are placed in a thinner diameter induction tube and are controlled at the same temperature. When the fluid flows, the gas brings some of the upstream heat to the downstream, while the downstream heater takes the temperature of the heat from above. At this time, the flow rate is measured using the principle that the temperature difference between the upper and lower heaters is proportional to the mass flow rate of the fluid." (Appendix: qm = KCpA △ T Cp Constant pressure specific heat capacity A measuring tube winding (ie heating system) and Thermal conductivity coefficient between ambient heat exchange systems; K --- meter constants
Imagine ... placing two sets of electric heaters, connecting two electric heaters with one wire, and sitting at the right-angled cross line at the midpoint of the line, it is warm. The two electric heaters dissipate the same amount of heat. You sit in the middle of the same distance from the two electric heaters and receive heat from both sides. This is where the temperature is high. In this hot season, when you say this, it's really unbearable... At this time, put an electric fan on the side, and the heat emitted by the side near the fan is blown to the farther electric heater. You sit. The place will feel a bit cooler. The faster the fan blows, the cooler it will be. This is the same as in the thermal sensor tube. The strength of the fan (air volume) = the flow rate of the gas. Conversely, if you want to detect flow, you can say "measure the amount of heat that moves between two electric heaters as the gas flows through."
Gas mass flow controller use
1. Fuel gas mass flow measurement control for boilers and crackers;
2. Measurement of mass flow of petrochemicals, oil production, and flare gas;
3. Combustion furnace air mass flow measurement control; gas turbine hydrogen mass flow and control;
4. Food processing and beverage gas mass flow and control;
5. Water plant cl2 mass flow control;
6. High purity gas mass flow measurement when producing semiconductors;
7. Mass flow measurement of catalysts and chemical additives;
8. Pump protection control, pump seal, lubrication pool leak detection;
9. Air-conditioning system control;
10. The instrument uses air, process air, nitrogen, and other mass flow measurements.
11. Gas Analyzer, Atmosphere Sampler
12. Leakage monitoring
13. Gas Distribution System
14. Laboratory Gas Measurement
15. Medical Applications
16. Fuel Cells
17. Apply gas: Air, O2, N2, He, Ar, CO2, H2, CH4, C3H8, N2O, SF6, C3H6, CO, C4H10, etc.
In actual use, it is found that when the input gas is different, the value displayed by the control does not correspond to the actual value. In fact, the reason is very simple, because in the MFC industry, there is a parameter called CF, that is, the gas conversion coefficient (hereinafter referred to as CF). In the MFC industry, N2 (nitrogen) is defined as the standard gas M. The C2 value of N2 is 1.00, and other gases are centered on nitrogen and are distributed around 0.1 to 1.4.
Typical gases with a CF greater than 1.00 are the monoatomic gases He (helium), Ar (argon), Kr (tantalum), and Xe (tantalum). Gases similar to N2 include 02 (oxygen), H2 (hydrogen), and F2 (fluorine). Below 0.5 there are SF6, WF6, SiCl4 and so on. If it is a mixture of several gases, simply analyze the ratio and use the respective CF value.

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