Study on a Concentration Sensor with a Hot Wire to Measure the Composition of a Binary Gas Mixture

摘要

The present experimental study is an attempt to measure the concentration of jet diffusion. A hot-wire concentration sensor is used to measure the concentration of the components in a binary mixture of gases. King's equation, which gives the heat transfer from a fine wire heated by Joule heating in a gas flow with a low Reynolds number, includes two main parameters, velocity and thermal conductivity. The effect of velocity is suppressed by the passage of gases through a sonic nozzle. Thus, in the hot wire, the influence of thermal conductivity exceeds that of velocity. The concentration probe is calibrated using a helium jet and a carbon dioxide jet. The calibration curve is prepared using a helium-air mixture and a carbon dioxide-air mixture. The time constant of the probe is measured to be 0.74 ms for helium and 3.48 ms for carbon dioxide. The contours of velocity and concentration of helium and carbon dioxide gases are measured.