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.