Velocity Measurement of Air Flow Using Temperature Fluctuation

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Other Title
  • 温度ゆらぎを利用した気体の流速測定

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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.<br>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.<br>The main features of this method for, the measurement of the air flow velocity are as follows:<br>(1) The method using temperature fluctuations is more advantageous than tracer injection methods, becausee it does not contami nate an object.<br>(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.<br>(3) This method requires some time interval for averaging times, since the correlation method is used to obtain the flow velocity.<br>(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.<br>Moreover, when vl is smaller than the abovementioned values, the errors are systematic Thus this method is still useful with compensation.<br>The velocity measurement by this method is applicable in various fields of flow.

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