Mechanism of Ammonia Stripping Intensification via Jet Impact Under Vacuum: A Multi-Scale CFD Study on Vortex Evolution and Energy Dissipation

Conventional air stripping for ammonia–nitrogen wastewater is often hampered by packing clogging and low mass transfer efficiency. To address these limitations, this study proposes a jet impact negative pressure reactor (JI-NPR) featuring an optimized scatter-pattern (D7) multi-orifice configuration. Computational Fluid Dynamics (CFD) simulations were employed to systematically investigate the effects of Reynolds number (Re = 5503.4~9651.0, corresponding to 2.76~4.84 m/s) on the hydrodynamic characteristics and deamination performance. Results indicate that increasing jet velocity significantly enhances the water volume fraction, resultant velocity, and pressure core intensity within the impact zone. Notably, these enhancements are maximized at the second row (z = 146 mm), attributed to reduced interference from the negative-pressure flash evaporation region. While a higher Re promotes interfacial renewal and vortex evolution, thereby enhancing mass transfer, it also intensifies energy dissipation and reduces the uniformity of the turbulent kinetic energy distribution. This work elucidates a critical trade-off between mass transfer enhancement and energy consumption, establishing a quantitative structure: the Re–flow field-performance relationship. The findings provide a theoretical foundation for the design and optimization of energy-efficient, high-performance wastewater treatment systems.