Direct measurement of droplet breakage in a pulsed disc and doughnut column

Abstract

The lack of experimental data for the droplet breakup has been one of the limitations for the application of population balance model (PBM). In this work, a high‐speed camera was used to directly measure the droplet breakup frequency and daughter size distribution in a pulsed disc and doughnut column. It was found from the captured video that multiple breakup events were more frequently observed than binary breakup. The multiple breakup was treated as an original breakup and several intermediate breakups to characterize the process quantitatively. The effects of pulsation intensity, dispersed phase flow rates, and the spatial locations were investigated in detail. Empirical correlations were finally established for both the breakup frequency function and the daughter droplet size distribution function and fitted well with the experimental data. The correlation equations were then used in a simplified PBM to calculate the droplet number density, which further proved the feasibility of the correlations. © 2017 American Institute of Chemical Engineers AIChE J, 63: 4188–4200, 2017

Experimental study on drop breakup time and breakup rate with drop swarms in a stirred tank

“…Ashar et al 36 Recently, experiments have been carried out by Li's group to directly measure the breakup rate in a pulsed column [38][39][40]44 and in a pump-mixer. 45,46 In the above study, the multiple breakup process is treated mathematically as a sequence of the binary breakup.…”

“…Those works were performed with various systems, operating conditions, and different experimental facilities. The topic mainly focused on the following aspects: breakup possibility, [24][25][26][27][28][29][30][31] number of fragments, 24,25,28,[32][33][34][35][36][37] daughter drop size distribution,, [24][25][26]28,29,33,35,[38][39][40] and so on. Despite numerous efforts have been devoted to investigate drop breakup, it is still a long way to adequately understand breakup phenomena due to the complexity of breakup dynamics in turbulent liquid-liquid dispersions.…”

Experimental measurement of bubble breakup in a jet bubbling reactor

“…Liu et al 21 studied the droplet breakup in a pulsed disc and doughnut column through experiments, and the breakup frequency function and daughter droplet size distribution function were correlated with the shear stress. Zhou et al 22 established the correlations of the droplet breakup frequency and daughter droplet size distribution with the pulsation intensity in a pulsed disc and doughnut column. Zhou et al 23 experimentally determined the droplet breakup in a pump-mixer, and the correlation of the droplet breakup frequency with the Weber number, Froude number, and Reynolds number was proposed.…”

“…Coulaloglou and Tavlarides 18 defined the bubble breakup frequency as the ratio of the breakup probability to the breakup time, which was widely used to experimentally calculate the breakup frequency. [21][22][23][24] The breakup probability is the ratio of the number of bubbles that break up to the total number of bubbles and increases with the turbulent dissipation rate and the size of mother bubbles. [25][26][27] There are two definitions of the breakup time in the literature, introduced by two breakup event definitions.…”

“…As the mother bubble size increases, the interfacial energy of the bubble per unit volume decreases. When the u j is the same (the same ε), the bubble is more likely to be broken up to increase the interfacial energy per unit volume,22 so the bubble breakup probability increases with the mother bubble size.The bubble breakup frequency is calculated through Equation(5), which is the breakup probability divided by breakup time. In this work, we adopt the cascade breakage definition when defining the breakup pattern.…”