Thermoanemometer

Diagram of experimental drying tunnel (1) test section, (2) fan, (3) controller air flow, (4) heating element, (5) valve controller of gas, (6) thermometer of wet bulb, (7) thermoanemometer, (8) spheres, (9) video camera. 

The velocity of the air flow is measured most frequently by thermoanemometers. A sensitive semiconductor or resistance thermometric sensor is situated in the flow of the air sampled. The resistance of the sensor depends on the velocity of the air flow and the calibration is provided at a constant temperature with the help of a suitable flow meter. The disadvantage of the thermo-anemometers is the necessity for constant temperature for the period of particular sampling procedures and also the need for a time consuming calibration. Connection to a recorder is advantageous. 

The measurement of wj in Eq. (51) is usually made by thermoanemometer. As the length of the wire of this device is only several times smaller than the channel dimension in the packing in horizontal direction, the measurement of the real gas velocity in this case is not exact, i.e. the value of A is not ract either. The di d ssperimental error does not influence the value of the penetration depth. 

---