열식 유량계의 운전온도 범위 확장을 위한 센서부 열전달 계수에 관한 연구

Abstract

In order to measure gas flux, there are some techniques based on volume flux and mass flux. The mass flux measurement is more favored to measure correctly gas flux under the extremely - high thermal or extremely - low pressure conditions. The thermal mass flow-meter is the representative technique to measure mass flux. In designing the flow-meter, it is important to calibrate convectional thermal coefficient affected by flow velocities around sensor and thermal changes. To analyze quantitatively the convectional mechanism around cylinders in high thermal external flow , experiments are conducted through installing 40m3/min blower at 100 mm duct for high thermal gases and heater able to bring ambient gas up to 200 ℃. By using control valves at the end point of duct, we controlled fluid velocities. By installing Pt 100 sensor to the heater, fluid temperature is controlled. In this experiment, convectional coefficients around cylinders are proportional to velocity to the power of 0.45 . A and B in the correlation equation coefficients behaved independently at 105 ℃