Understanding and using thermal sensitive anemometers
The basic principle of a thermosensitive anemometer:
1. A metal wire anemometer is a device that places a thin metal wire in a fluid and heats the wire with an electric current to a temperature higher than the temperature of the fluid. When the fluid flows through the metal wire in a vertical direction, it will take away some of the heat from the wire, causing the temperature of the wire to decrease.
2. According to the theory of forced convection heat exchange, a relationship can be derived between the dissipated heat Q and the velocity v of the fluid. The standard probe consists of two brackets tensioned with a short and thin metal wire. Metal wires are commonly made of metals with high melting points and good ductility, such as platinum, rhodium, and tungsten.
3. According to different uses, the head is also made into double, triple, diagonal, and V-shaped threads X-shaped, etc. In order to increase strength, metal film is sometimes used instead of metal wire, and a thin metal film is usually sprayed on a thermal insulation substrate, which is called a hot film probe. The probe must be calibrated before use.
4. Static calibration is carried out in a specialized standard wind tunnel, measuring the relationship between flow velocity and output voltage and drawing a standard curve; Dynamic calibration is carried out in a known pulsating flow field, or by adding a pulsating electrical signal to the heating circuit of the anemometer to verify the frequency response of the line anemometer. If the frequency response is poor, corresponding compensation circuits can be used to improve it.
The purpose of a thermosensitive anemometer is:
1. The application of anemometers is very extensive, and they can be flexibly applied in all fields. They are widely used in industries such as electricity, steel, petrochemicals, energy conservation, etc. There are other applications in the Beijing Olympics, such as sailing competitions, rowing competitions, field shooting competitions, etc. anemometers need to be used to measure.
2. There are many industries that require the use of anemometers, and recommended industries to use include offshore fishing, various fan manufacturing industries, industries that require exhaust systems, and so on.
3. The working principle of the thermal sensitive probe of the anemometer is based on the cold shock airflow taking away the heat on the thermal element. With the help of an adjustment switch, the temperature is kept constant, and the adjustment current is proportional to the flow rate.
4. When using a thermosensitive probe in turbulence, airflow from all directions simultaneously impacts the thermal element, which can affect the accuracy of the measurement results. When measuring in turbulence, the reading of the thermal anemometer flow velocity sensor is often higher than that of the rotary probe.
The above phenomena can be observed during pipeline measurement. According to different designs for managing pipeline turbulence, it may even occur at low speeds. Therefore, the anemometer measurement process should be carried out on the straight section of the pipeline.
