Characterisation of mixing rate due to high power ultrasound

Abstract

For meaningful assessment of results from laboratory and pilot plant trials, it is often necessary to know the mixing characteristics within the ultrasonic reactors. Previous workers have used conductivity measurements in an attempt to characterize the residence time distribution in ultrasonic reactors, but these results do not provide direct data on the mixing within the high power region adjacent to the ultrasonic probe tip. We overcome this difficulty though direct visualization of the mixing process within the high energy region close to the tip of the ultrasonic probe. Our analysis proceeds by determining an approximate turbulent diffusivity in a batch reactor arrangement for different values of ultrasonic energy input.For input electrical power levels between 70 and 120 W and a processing volume of 30 ml, the effective turbulent diffusivity varied from about 0.2 × 10 −3 m 2 /s to 0.7 × 10 −3 m 2 /s. We demonstrate that such results can be coupled to a suitable dispersion model to estimate the actual residence time distribution in flow-though arrangements when the through-put adds little additional mixing energy. Therefore, coupling the effective turbulent diffusivity identified in a batch reactor with a suitable dispersion model for the reactor therefore offers an alternative approach to the deduction of RTD when determining the actual RTD in the high intensity zone of steady flow sonochemical reactors is problematic.

Ultrasonic mixing, homogenization, and emulsification in food processing and other applications

“…Nevertheless, this claim is generally connected with visual observations (Guo et al, 2007;Parvizian et al, 2011;Yusaf and Buttsworth, 2007), although rather few works have actually been devoted to the quantification of mixing under US using conventional engineering criteria. Nevertheless, this claim is generally connected with visual observations (Guo et al, 2007;Parvizian et al, 2011;Yusaf and Buttsworth, 2007), although rather few works have actually been devoted to the quantification of mixing under US using conventional engineering criteria.…”

“…Few works have been devoted to macromixing under US (Murugan and Nagarajan, 2008;Vichare et al, 2001;Yusaf and Buttsworth, 2007), probably because of a rather poor US effect. Both criteria (mixing time or σ 2 ) are obtained through tracer experiments.…”

“…Micromixing is linked to small-scale turbulence and velocity gradients, and, compared with macromixing, it is dramatically affected by intense cavitation when using power US (Yusaf and Buttsworth, 2007). Contrary to macroscopic hydrodynamics, micromixing cannot be measured directly because of microsensor limitations.…”

Evaluating the effect of heat transfer on cell disruption in ultrasound processes

“…The work can be divided into three major sections: (1) heat transfer through the ultrasound chamber, (2) suspension mixing time and residence time distribution (RTD), and (3) yeast disruption using ultrasound. The second part of this work was covered thoroughly by our previous paper (Yusaf and Buttsworth 2007).…”

Removal of Impurity Elements from Molten Aluminum: A Review

“…Saternus reviewed the influence of gas flow rate on the nucleation, growth, morphology and dispersion of bubbles in liquid metals in 2005 (Saternus and Botor 2005). Many studies and reviews for this phenomenon in the chemical process industry can be found (Cacciamani and Ferro 2001;Moucha, Linek, et al 2003;Hall, Barigou, et al 2005;Madan, Satish, et al 2005;Bomba and Zun 2006;Kumaresan and Joshi 2006;Montante, Bakker, et al 2006;Smith 2006;Takahashi, Tagawa, et al 2006;Ghionzoli, Bujalski, et al 2007;Hao, Wang, et al 2007;Masiuk and Rakoczy 2007;Montante, Paglianti, et al 2007;Murthy, Ghadge, et al 2007;Rielly, Habib, et al 2007;Rudolph, Schuer, et al 2007;Yusaf and Buttsworth 2007;Montante, Figure 44 Gibbs free energy for the reactions to remove impurity elements from aluminum by AlF 3 powder injection. Nemtsov and Zabaniotou 2008;Richter, Hoffmann, et al 2008).…”