Application of Knudsen Thermal Force for Detection of CO2 in Low-Pressure Micro Gas Sensor

Abstract

Development of new techniques for detection of CO₂ gas is significant for decrease the dangers of CO₂. In this research, numerical simulations are performed to evaluate the performance of a new micro gas sensor (MIKRA) for the detection of CO₂ gas. This device works due to temperature difference inside a rectangular enclosure with heat and cold arms as the non-isothermal walls at low pressure condition. In this study, the pressure of CO₂ is varied from 62 to 1500 Pa correspond to Knudsen number from 0.1 to 4.5 to investigate all characteristics of the thermal-driven force inside the MEMS sensor. In order to simulate a rarefied gas inside the micro gas detector, Boltzmann equations are applied to obtain high precision results. To solve these equations, Direct Simulation Monte Carlo (DSMC) approach is used as a robust method for the non-equilibrium flow field. Our findings show that value of generated Knudsen force significantly different when the fraction of CO₂ in N₂–CO₂ mixtures is varied. This indicates that this micro gas sensor could precisely detect the concentration of CO₂ gas in a low-pressure environment. In addition, the obtained results demonstrate that the mechanism of force generation highly varies in the different pressure conditions.