Abstract
A special CA thermo-pile with high sensitivity and fine frequency characteristics, of which the gain is flat to 10Hz, is developed as a sensor for measurement of temperature fluctuations.
The irregular temperature fluctuations produced around a heater are convected by air flow and detected by the two sensors provided along the flow. Using the distance between two sensors and a cross-correlation function of the two signals, the flow velocity is calculated.
The main features of this method for, the measurement of the air flow velocity are as follows:
(1) The method using temperature fluctuations is more advantageous than tracer injection methods, becausee it does not contami nate an object.
(2) In the region of 0.5m/s∼10m/s, measurement of the flow velocity is possible if the velocity is calibrated with a standard flow meter.
(3) This method requires some time interval for averaging times, since the correlation method is used to obtain the flow velocity.
(4) The relative error of this measurement is as small as ±5% when the product (vl) of the distance between two sensors (l) and the flow velocity (v) is greater than 0.12 for l=10cm, and 1.40 for l=30cm.
Moreover, when vl is smaller than the abovementioned values, the errors are systematic Thus this method is still useful with compensation.
The velocity measurement by this method is applicable in various fields of flow.
