Gas expansion patterns in the reacting submerged gas jet into liquid

Abstract

The reacting submerged gas jet into a liquid bath is applicable in many industrial processes. The jet is featured with violent gas expansions due to the gas momentum and the liquid evaporation caused by the heat released from the chemical reaction. The gas expansion dictates the gas–liquid interface fluctuation that is closely related to the break-off of the gas phase, gas/liquid reverse flow, and back attack phenomenon. These phenomena are typically hazardous in actual applications. Gas expansion and its underlying mechanisms remain unclear. We experimentally studied the reacting submerged gas jet into a liquid with a HCl/aqueous ammonia system at different liquid temperatures. Results indicate that two expansion patterns exist: the attached expansion pattern and the detached expansion pattern. At the liquid temperature of T = 21 °C, only the attached expansion pattern occurs. At T = 57 °C, both the attached and detached expansion patterns arise. Under the attached expansion pattern, the break-off happens close to the nozzle, and the back attack phenomenon typically occurs. Under the detached expansion pattern, the break-off happens away from the nozzle, and almost no back attack occurs. Subsequently, gas–liquid interface fluctuations at different liquid temperatures were compared. At T = 57 °C, the interface dynamics near the nozzle differs from that away from the nozzle. Finally, the dimensionless number Str Φ=(fd0/u) ΔH/(CpΔT) was proved to have no dependence on the liquid temperature. It is a proper number to describe the dimensionless frequency of the periodic oscillation of the gas-phase length at base frequency.