Numerical Simulation of Acoustic Field during Ultrasound-assisted Extraction
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Abstract:
In this study, a multi-physics coupling model of ultrasound-assisted extraction (UAE) was established, to visualize the acoustic field distribution of the ultrasonic extraction equipment set at a certain power but different frequencies. The effects of different frequencies and transducer arrays on the uniformity of acoustic field were studied. The reliability of the model was verified by comparing the extraction rates of soybean protein at different frequencies. The simulation results showed that the uniformity of the acoustic field could be improved via frequency modulation by the cylindrical 5-frequency ultrasonic device, but the absolute sound pressure decreased accordingly. A low frequency of 20 kHz and resonance frequencies of 28 kHz and 35 kHz would easily cause cavitation effects, indicating an increased extraction rate. The experimental results showed that the extraction rate of soybean protein was significantly increased (p<0.05) by the ultrasonic treatment, and the increase of frequency led to a gradual decrease of extraction rate. Under the same conditions, the extraction rate of proteins sonicated at 20 kHz, 28 kHz or 35 kHz was 28.75%, 26.78% and 18.28%, respectively, higher than that obtained by traditional alkali extraction. This study also proposed that when transducers were arranged in a rectangular shape and extraction was performed at a resonant frequency, the outcome of extraction was more desirable. Numerical simulation reduces testing costs and provides a new method for frequency screening, process optimization and equipment improvement.
