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

Abstract

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 scaleup. 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 /(kW•s), which is equivalent to or even better than that in the gas−liquid system.