Numerical investigation of supersonic separator's performance in natural gas dehydration

In this study, a validated computational fluid dynamics code was established to investigate the condensation of a binary CH4–H2O mixture in a supersonic separator. The condensation parameters were numerically calculated, and then the influence of divergence angle, swirling intensity, and H2O mass fraction on efficiency was evaluated. The results showed that increasing the divergence angle raised the nucleation rate and moved the location of nucleation toward the throat. In addition, increasing the divergence angle enhanced the droplet number but it decreased the droplet radius. Because of these effects, an increase in the wetness fraction at the nozzle outlet by 5.7% was attained. Also, the results demonstrated that increasing the swirl intensity pushed the nucleation place toward the nozzle throat. It means that the more substantial the swirl intensity, faster the nucleation. Furthermore, the maximum nucleation rate was increased by enhancing the swirling intensity. The droplets number was increased by enhancing the swirl intensity, which caused to higher the wetness fraction by 1.2%. It was also found that although both methods improved the efficiency of the supersonic nozzle by increasing the water mass fractions, the inlet flow swirling method performed better than the divergence angle changing method. An optimal case was introduced by using the technique for order of preference by similarity to ideal solution method. The criteria were outlet wetness fraction, kinetic energy, and pressure loss ratio. Finally, the proper location for wet outlet was determined. The result showed that the supersonic separator that has a wet outlet closer to the throat is more efficient.