Why should the flowmeter be temperature and pressure compensated?
Vortex flowmeters need to compensate for temperature and pressure when measuring gases, mainly for the following reasons:
1. Compressibility of the gas
The gas has a large molecular spacing, is highly compressible, and its density is significantly affected by temperature and pressure. According to the ideal gas equation of state (where is the pressure, is the volume, is the amount of matter, is the molar gas constant, is the temperature), a change in temperature and pressure leads to a change in the volume and density of the gas while the amount of the substance is constant. For example, when the pressure increases, the gas molecules are compressed, the number of molecules per unit volume increases, and the density increases; As the temperature increases, the volume of the gas expands and the density decreases.
2. Ensure the accuracy of measurement
Differences from standard condition: Gases are usually settled in standard volume flow, while the actual measured temperature and pressure are often different from standard conditions. If the temperature and pressure are not compensated, the calculation is directly based on the measured volume flow, which will deviate greatly from the actual flow rate under standard conditions.
Limitations of the Flowmeter Measuring Principle: Vortex flowmeters calculate the flow rate by measuring the difference between the velocity and pressure of the gas at the vortex. When the temperature and pressure of a gas change, its density changes, and the actual mass flow rate will be different even if the vortex frequency is the same. If the flow rate and flow rate are calculated only based on the frequency of the detected vortex, and the density change is not taken into account, the measurement results will be inaccurate. For example, in the process of natural gas transportation, pipeline pressure fluctuations and ambient temperature changes frequently, if not compensated, the metered natural gas flow error will be large, affecting the accuracy of trade settlement and production process control.
3. Meet the needs of industrial applications
Improve the accuracy of production process control: In industrial production, many processes require precise control of gas flow to ensure product quality and production safety. For example, in chemical reactions, the flow rate of gases involved in the reaction needs to be accurately controlled, and accurate flow data can be ensured through temperature and pressure compensation, so as to stabilize the production process, improve the consistency of product quality, and avoid product quality problems or production accidents caused by inaccurate flow control.
Easy data comparison and statistics: Temperature and pressure may be different when measuring gas flow at different times and locations. Temperature and pressure compensation can uniformly convert the measurement results to the standard condition, make the data of different measurement points comparable, facilitate data statistics, analysis and management, and provide an accurate basis for production scheduling and energy accounting.
