The mechanisms of thermal diffusion and baro-diffusion effects on thermacoustic mixture separation

Thermoacoustic separation is a totally new method for separating gas mixtures and is also considered as an effective mean of separating even isotopes and azeotropes. In this paper, a two-dimensional numerical method based on the compressible SIMPLE algorithm has been developed to study the mechanisms of thermal diffusion and baro-diffusion effects on thermacoustic mixture separation. It is found that the numerical results are in good agreement with experimental data and theoretical predictions from published literatures. Furthermore, contributions of thermal diffusion and baro-diffusion to thermoacoustic separation are studied, respectively. It is shown that only the radial gradient can cause separation of mixture and thermal diffusion caused by radial temperature gradient performs as the main driving force of thermoacoustic separation. Thus, temperature, velocity, and concentration distributions along the radial direction have been studied to investigate the detailed process of thermoacoustic separation in the resonator. Under the combined action of sound wave and thermal diffusion, the heavy component is driven into pressure node during the expansion half cycle and the light component is driven into velocity node during the compression half cycle, making the mixture separated in the axis direction.