Determination of flow direction by a globe-sensor containing thermal anemometers.

Conventionally used thermal anemometers are able to measure velocity, but cannot determine direction. In the present study, a new kind of thermal anemometer is presented which consists of a 38mm-diameter sphere with 12 NTC resistances on its surface. Each of them is a single Constant Temperature Anemometer which takes measurements of the local heat transfer on the surface depending on the position on the ball. The calibration of this sensor is taken in 325 different directions for 6 velocities by an automatic calibration system which provides curves of the heat transfer depending on the air flow angle. The simultaneous measurements of the 12 Constant Temperature Anemometers are compared with the data of the calibration and so the value and the angle of the air flow are determined. This se&or allows the measurement of air velocities over a range of 0.05m/s to 6m/s and of the flow angle over the entire room angle of 360°. So it is possible to obtain information on the value as well as the direction of the air velocity. This new measurement method makes a contribution to a better description of indoor air flow. Using this sensor, it is also possible to check the results of computer programs simulating indoor air flow.