Application of Knudsen thermal force for detection of inert gases

Abstract

Recently, detection and analysis of gas mixtures have become significant for purifications and separation of the natural gas mixture. In the present work, Direct Simulation Monte Carlo (DSMC) method is applied to evaluate the performance of a new micro gas sensor (MIKRA) for mass analysis of three inert gases (Helium, Neon and Argon). This sensor applied the Knudsen force induced by temperature difference at the low-pressure condition to diagnose the main components of the mixture. Since this sensor works in low-pressure condition, Boltzmann equation is used to attain accurate outcomes. To solve these equations, Direct Simulation Monte Carlo (DSMC) approach is used as a robust method for the non-equilibrium flow field. This study performed comprehensive studies to disclose the primary process of force production and applied this for the analysis of the gas mixture. Hence, effects of the main parameter such as temperature gradient and the gap of arms are expansively examined in different ambient pressures. Furthermore, the influence of various mixtures of the (Helium, Neon and Argon) on force generation is also investigated. Our findings show that value of generating Knudsen force significantly varies when the component of the mixture is changed. According to obtained results, the Knudsen force declines as the molecular weight of the gas decreases. In addition, the induced force is highly proportional to the molecular weight rather than other characteristics. Therefore, the Knudsen force is a reliable method for the mass analysis of the mixtures. Keywords: Knudsen force, Mass analysis of gas mixture, DSMC, Low-pressure gas actuators, MEMS