In this paper, a novel piston exchanger—reciprocating-switcher energy recovery device (RS-ERD) was introduced and developed. The RS-ERD adopts the unique open/close plate design, which not only ensures a perfect sealing effect and high efficiency of the device, but also favors avoiding the destruction of micro-particles in the liquid occasionally. For proving the operating performances of the RS-ERD, an emulating RO-ERD desalination platform was established and the testing conditions were regulated as ERD capacity of 30 m³/h and operating pressure of 6.5 MPa. The experimental results indicate that the operating stability of the RS-ERD is good. The leakage ratio of the device is lower than 1.7% and the energy recovery efficiency is above 98%, which can satisfy the industrial requirements of the SWRO plant.

The gas–liquid Venturi injector has been widely applied in industrial production due to its advantages of high entrainment and low energy consumption. In this study, Computational Fluid Dynamics (CFD) was employed to investigate the effect of the gas–liquid interface structure within the mixing section on entrainment behavior by varying the geometry of the mixing section during gas–liquid coaxial flow. The simulation results indicate that along the jet direction, the gas–liquid interface generally transitions from a smooth cylindrical shape to a lobed structure in the mixing section. Surface waves mainly appear in the lobed region. Furthermore, lobed and surface wave structures reduce pressure loss and enhance entrainment. Additionally, the study found that longer mixing sections enhance entrainment under low flow resistance. This study provides valuable insights for achieving high jet entrainment and offers supplementary research on gas–liquid interface structures in jets constrained by solid boundaries.