Experimental study of the hydrodynamic behaviour of a high frequency ultrasonic reactor

Abstract

In relation to design and modeling of sonochemical reactors, the hydrodynamic behaviour of a high-frequency ultrasonic reactor has been investigated. Residence time distribution (RTD) measurements have been performed by means of a tracer method. The influence of ultrasound on the response to an inlet pulse was evidenced. It was shown that the reactor behaves like a completely stirred tank reactor (CSTR) as soon as ultrasonic irradiation operates. Preliminary observations on acoustic streaming occurring within the reactor will also be presented.

Characterization of flow phenomena induced by ultrasonic horn

“…The fluid velocities in the vicinity of ultrasound horn were found to be in the range of 0.3-0.5 ms −1 . Gondrexon et al (1998) have investigated the acoustic streaming in high frequency transducer (500 kHz, diameter 0.04 m) with visual qualitative observation in a PVC cylindrical body (diameter 0.10 m, height 0.10 m) equipped with a stainless steel plate fixed to the bottom (diameter 0.15 m, thickness half a wavelength 5.84 × 10 −3 m). The transducer is stuck to the stainless steel plate.…”

Comparative study on effect of mechanical mixing and ultrasound on the performance of a single up-flow anaerobic/aerobic/anoxic bioreactor removing CNP from milk processing wastewater

“…It was accepted that a stable cavitation and an important fluid hydrodynamic effect named micro streaming could be created in the fluid by the high-frequency ultrasonic irradiation [36]. These phenomena generate a fluid movement at along of transducer axis by the name of acoustic fountain since they hit the upper surface and return to the fluid improving the microbial flocculation and afterward shorten the settling time with the low height of sludge in the bioreactor [37].…”

Characterisation of mixing rate due to high power ultrasound

“…There are many standard techniques for the measurement of RTDs which usually involve introducing a tracer element (such as a saline solution or a dye) at the entrance to the processing device and measuring the concentration of the tracer just downstream of the vessel [5,6,7]. Measurements of the RTD in ultrasonic processing configurations have been performed using such tracer methods [8,9].…”

“…In the work of [8], a NaCl tracer pulse was injected into the inlet stream entering their ultrasonic cell.…”

“…In contrast to the arrangement of [8], the configuration of [9] had a characteristic performance between that of a plug flow reactor and a CSTR. For continuous flow arrangements, there are establised methods for estimating an effective turbulent diffusivity or as a nondimensional parameter, the vessel dispersion number, based on an appropriate dispersion model and the measured RTD [5,6,7].…”