The Study Of The Magneto-hydrodynamic Characteristics Of Thermal Magnetic Type Oxygen Sensor

The oxygen sensor plays an important role in evaluation oxygen content in the mixture ofindustrial production processes, such as chemical engineering, gas splitting, glass productionprocess, and other processes protection gases are used. Its applications are widening withimprovement of technology. Thermal magnetic type oxygen sensor uses the paramagneticcharacteristic of oxygen gas, still occupies a very important position in the current oxygenconcentration analysis. This kind of sensor can satisfy all kinds of requirements of tracingoxygen. As a branch of oxygen measurement instrument, it is a mature technology. Comparedto other electrochemical sensors, this type sensor has the advantage of no running loss,continuously measuring for a long time and a longer service life. Thus, the thermal magnetictype oxygen sensor is widely used in almost all cases that the concentration of oxygen gasaffects greatly the quality of the products and the efficiency of production. The thermalmagnetic type oxygen sensor based on the convection produced by the magnetization force inparamagnetic gases under non-uniform magnetic field and temperature field. The sensingmechanism is very complicated. In order to improve the accuracy, it is necessary to study thesensing mechanism in details. Thus, this paper uses a numerical method to study the magneto-hydrodynamic characteristics of thermal magnetic oxygen sensor.The contents of present study include: to develop a numerical to determine the magneticfield produced by the complex geometry permanent magnets; to establish the mathematicalmodel of the thermal magnetic type oxygen sensor; to develop a numerical method; to analyzemagneto-hydrodynamic characteristics of gas containing oxygen. Through these works, thesensing mechanism of the thermal magnetic type oxygen sensor is analyzed in details.The results show that only when the pressure difference between the inlet and the outletof the tube is less than0.014Pa, the thermal magnetic convection is obvious, thermalmagnetic convection increasing average flow velocity of fluid flowing through the test tube,under the condition of constant heating, thermal magnet convection slightly increases heattransfer coefficient. These factors decrease the wall temperature greatly, and the decrease ofthe wall temperature is strongly related to the oxygen concentration of the mixture gases.Thus, increasing average flow velocity and enhancing heat transfer are the sensingmechanisms of the sensor. When the oxygen concentration of the fluid changes from0%to100%, the average flow velocity of fluid increases about70.7%; the temperature of the tubewall has a variation of15.03°C, the relationship between the wall temperature change and theoxygen concentration can be in a good linearity if the oxygen concentration region is dividedinto two regions:0-30%and30%-100%, the linearity of this relationship is5.05%in theregion0-30%, and5.66%in the region30%-100%. If change of the electricity resistance of the wire is used to transform the temperature change, the corresponding resistance change isof1.5, the resolution of the sensor is about0.0067%for the configurations studied.