Modern heaters are significantly different from the old. They are reliable, have a wider dynamic range and do not need time for the dismantling for verification. Although everything remained inside, as it was: pressure sensors, temperature and expenses and heat computers. The main component is the flow sensor, and the choice of the device depends on the flow rate of the component.
On large -diameter pipelines, flow meters are used that measure steam consumption, measuring the pressure drops on the narrowing device. They use an ultrasound or electromagnetic method for measuring fluid flow rate.
Electromagnetic expenses do not have mobile parts, differ in a wide dynamic range and high accuracy of flow measurement, do not depend on changes in the pressure, viscosity and temperature of the working environment, do not present special requirements for the flow profile and areas without hydraulic resistance, in addition, they can be removed and installed, Without stopping the coolant. At the same time, they are expensive, complex, consume a lot of electricity, do not give the opportunity to measure the consumption of condensate and non -conductive media.
Ultrasonic dimensions, like electromagnetic, are not equipped with mobile parts, have a wide dynamic range and high accuracy of expenses, at the same time can measure condensate and demineralized medium, are relatively inexpensive and can be used with patch primary cost sensors. From the minuses, we note that they need to compensate for the indications of measuring temperature, pressure and viscosity of the working environment, are difficult to install, make high requirements for areas where there are no hydraulic resistances, and their work may also be violated if a large amount of precipitation is postponed on the inner surface of the pipe.
Ultrasonic measurements can be carried out temporary, frequency, correlation or doppler methods.
The temporary method is based on ultrasound signals that are sent by stream and against it to the acoustic channel of the device. The difference in the signal passes determines the flow rate of the fluid. When using the frequency method, two signals are analyzed, which go by stream or against it. The period of repetition of the signals is equal to the spread of ultrasound, and the variable frequency is proportional to the flow rate. These methods allow to ensure high speed of flow meters and high measurement accuracy. At the same time, the quality of measurement depends on the properties of the fluid, the distribution of velocity by the fluid flow and the correct installation of primary converters.
The main principle of correlation methods is the definition of the time during which the heterogeneity of the flow moves between the two sections of the pipeline. The fluid speed is similar to the appearance of approximate modulation signals in different sections. These methods are almost independent of the properties of the fluid, the state of liquids, etc.D., But in this case, it takes more time to reaction to change in consumption.