A comparative study of gas flow patterns and gas-liquid separation performance in two types of swirl tubes

Guide-vane swirl tubes are widely employed as compact centrifugal separators in gas–liquid systems. This study presents a systematic comparative investigation of reverse-flow swirl tubes (RST) and uniflow swirl tubes (UST) to delineate their respective flow characteristics and separation performance under identical geometric conditions. A combined approach of CFD simulations and experimental measurements was employed, with the numerical model being validated against pressure-drop data. At V in = 7.5 m/s and C in = 10 g/m 3 , a stable rotating liquid ring was observed in the RST, whereas no such phenomenon occurred in the UST. For both configurations, the separation efficiency exhibited a non-monotonic trend with increasing inlet velocity, initially rising and then declining. Notably, the UST attained its peak efficiency at a higher velocity and demonstrated superior operational flexibility over a broader range of flow conditions. Reducing the guide-vane outlet angle enhanced the separation efficiency for both designs, albeit at the cost of increased pressure loss due to heightened swirl intensity. The pressure drop for both separators scaled approximately quadratically with inlet velocity, with the UST consistently exhibiting lower resistance. These findings offer useful insights for the selection and geometric optimization of swirl tube separators in response to varying process conditions.