Evaluation of optimum modes of ultrasonic pulsed influence for coagulation in liquid-dispersed medium

Abstract

This paper proposes a new approach to improve the efficiency of coagulation of dispersed particles in liquid. The approach is based on the ultrasonic treatment as a sequence of wave packets (ultrasonic pulses) of finite duration that is less than cycle period. The impact of ultrasonic pulses reduces the maximum cavitation nuclei radius achieved during direct diffusion of dissolved gas into the cavitation bubble interior. This leads to an increase the threshold intensity required for cavitation and hence to increase the maximum allowable ultrasonic energy that permits particles coagulation at stable cavitation absence mode. To determine the optimal ultrasonic pulse exposure modes (intensity and pulse duration) to ensure the most effective coagulation, a model is proposed and developed. The model initially considers the formation of cavitation nuclei to evaluate limit ultrasound exposure intensity realizing cavitation absence mode and then the convergence and coalescence of particles to evaluate their dispersed composition evolution during time. Evaluated exposure modes provide acceleration of coagulation up to 1.5 times during sonication in pulse mode in comparison with continuous exposure.