Process sound/flow energy

Table 3.8 Process intensification effects of cavitation based on sound and flow energy. Source adapted from Cogate [151].

In the process of sonication, electrical energy is converted into mechanical energy. The sound waves produce cavitation (the process of formation and collapse of microscopic bubbles) which leads to great mechanical shear forces. Particles are hammered to form smaller particles, and the increased energy of the system can promote chemical reactions. Ultrasonic chemistry has recently been reviewed [34]. Most research in sonichemistry has been carried out in ultrasonic cleaning baths. Operations on scale can be carried out by using commercial flow cells [35],... 

Behind the shock front various relaxation processes occur in the potential and the kinetic energies. The potential energy relaxation is associated both with thermal relaxation (see below) and with structural rearrangement within the system. Structural relaxation generally occurs at a speed considerably lower than that of the shock front (e.g., plastic flow), but it may be as fast as the shock front (e.g., martensitic transformation). It is accompanied by stress relaxation which occurs at the appropriate speed of first sound. 

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