Method for measuring wind speed in high and low temperature test chambers
There are several methods for measuring wind speed in high and low temperature test chambers, including:
1. The oldest instrument is the wind cup anemometer, which is mostly used in the meteorological field. The cross arm of the wind cup rotates at different speeds under different wind speeds to determine the size of the wind speed. The wind cup anemometer has a wide range of applications. Nowadays, many sizes of wind cup anemometers can measure air velocity in small volumes such as test chambers, without the use of small anemometers.
2. A thermometer is a special type of glass thermometer designed based on the cooling effect of flow. The measurement principle is to determine the wind speed at a certain point by the time it takes to cool the first heated thermometer to a certain temperature (such as cooling from 38 degrees to 35 degrees). However, since the thermometer must be reheated after each measurement, this method is more cumbersome.
The measurement principles of hot wire anemometers and hot ball anemometers are also designed based on the convective cooling effect. These two anemometers provide a quantitative electrical power to the measuring component during measurement, so that the measuring component reaches a predetermined standard temperature. When air flows through the component, the temperature of the component decreases, and the speed of the air can be determined based on the extent of the component's decrease. The hot wire measuring component is made of platinum wire winding, In many cases, the measurement component of a hot bulb anemometer is a negative temperature coefficient resistance. Due to the existing small size and small thermal capacity components, the thermal time constant of the measurement component can be obtained very small. At the same time, it can measure the airflow velocity on a very small cross-sectional area, which is particularly useful for low wind speeds. Currently, the temperature measurement range applied is between -30 degrees and 100 degrees. In hot wire anemometers, The cooling effect of the hot wire component depends on the angle between the spool and the airflow direction. When the airflow is equal to the hot wire direction, the cooling effect is the worst. By rotating the hot wire anemometer to measure the component, the airflow direction can be accurately determined.
Wind cup anemometers and thermometers can only be used in large laboratories where people can enter, while hot wire anemometers and hot bulb anemometers can be used in small high and low temperature test chambers.
