Ultrasonic separation of suspended particles— Part II: Design and operation of separation devices, Acustica

Separation of suspended particles by means of acoustic forces is a promising alternative to conventional technologies. This paper concerns some of the latest developments of separation devices based on piezoelectric resonators. The acoustic forces on particles suspended in a liquid are reviewed. A mathematical model for the description of layered piezoelectric resonators is extended and applied to the calculation of the electrical properties and the acoustic field quantities of the resonator. A resonator for particle separation is analyzed and the optimum operating frequency range with respect to resonator efficiency (performance number) is determined. It is found that efficiency depends strongly on the frequency and the properties of the suspension. Results are in good agreement with experimental data and with a different approach based on perturbation theory. PACS no. 43.35.Zc, 43.35.B