Numerical study of the sensing mechanism of the oxygen concentration sensor based on thermal magnet convection

Magnetic oxygen concentration analyzer based on thermal magnet convection is suitable for automatic measurement of the oxygen concentration in all kinds of industrial gases. In this paper, the sensing mechanism of the analyzer is numerically studied. The studied analyzer includes a horizontal circular tube, and an external magnet field produced by two permanent magnets. The results show the sensing mechanism of the analyzer is that thermal magnet convection greatly increases the average velocity of fluid flow through the tube and increases slightly the heat transfer coefficient. As results the wall temperature decreases, and this temperature decrease is strongly related with oxygen concentration. If the wall temperature is measured, the concentration of oxygen can be obtained. It is found that only when the pressure difference between the inlet and the outlet of the tube is less than 0.014 Pa, the thermal magnetic convection is obvious. The relationship between the wall temperature change and the oxygen concentration can be in a good linearity if the oxygen concentration region is divided into two regions: 0-30% and 30%-100%. The resolution of the sensor based on thermal magnetic convection is about 0.0067% for the configurations studied.