Performance Evaluation and Scale-up of the Swirl-Venturi Microdroplet Generator

The droplet generator is a key piece of equipment to strengthen the liquid-liquid reaction process. Studies have shown that the swirl-Venturi microbubble generator (SVMG) has a good microbubble generation effect. Based on this idea, a swirl-Venturi droplet generator is designed. The parameters of the SVMG, such as pressure drop, droplet size distribution, and liquid volume mass transfer coefficient k(L)a, are measured in a white oil-water system using the pressure difference, high-speed camera, and concentration tracer methods. First, combined with the CFD simulation, a strong internal circulation flow in the SVMG is found, which leads to a pressure drop of 25-34 times that of the traditional Venturi generator at the same flow rate, and the pressure drop model of the SVMG is established. Second, the Sauter average size d(32) of the droplets produced by the SVMG decreases with an increase of the Reynolds number of the continuous phase or a decrease of the Reynolds number of the dispersed phase. Considering the Reynolds number, flow rate, input power, and input power per unit volume of the continuous phase as scale-up criteria, it is found that the scale-up effect of the SVMG is the smallest only when the input power per unit volume is the same and the energy consumption of the size scale-up is higher than that of the quantitative scale-up. An empirical correlation between d(32) and the input power per unit volume is established. Finally, the energy efficiency of the SVMG is evaluated with k(L)a/(P/V) as an index, and the optimal energy efficiency is 0.80 m(3)/(kWs), which is equivalent to or even better than that in the gas-liquid system.