Physical Principles of Ultrasonic Technology Volume 2

Under the action of acoustic vibrations a liquid is converted into the aerosol state at the interface between a gaseous and a liq­ uid medium. Acoustic energy can be delivered to the atomization zone either on the liquid side or on the gas side. Ordinarily, when acoustic energy is delivered through the gas, the atomization of the liquid is realized by sonic and low-frequency ultrasonic vibra­ tions because high-frequency ultrasound is rapidly damped in prop­ agation through gases. But if the acoustic energy is delivered through the liquid, whose damping factor is orders of magnitude smaller than in gases, atomization can be realized by sonic, low­ frequency ultrasonic, or high-frequency ultrasonic vibrations. The following is a convenient classification of methods for the ultra­ sonic atomization of a liquid: 1. atomization of the liquid with the transmission of acoustic energy to the working zone through the liquid: a. atomization in a layer; b. atomization in a fountain; 2. atomization of the liquid with the transmission of acoustic energy to the working zone through the gas. 3 Chapter 1 Acoustic Atomization of Liquids The atomization of liquids by ultrasound (at a frequency of 300 kHz) was discovered in the classical studies of Wood and Loomis [1]. The first experimental investigation of the physical nature of the 8tomization of a liquid by ultrasound was conducted by Sollner [2].

of Volume 2.- V — Aerosol Production.- 1 — Acoustic Atomization of Liquids.- 2 — Atomization of a Liquid in a Layer.- 3 — Atomization of a Liquid in a Fountain.- 4 — Physical Mechanism of the Atomization Process.- 5 — Energy Aspects of the Acoustic Atomization of a Liquid.- 6 — Prospects for the Industrial Utilization of Acoustic Atomization.- VI- The Free-Gas Content of Liquids and Methods For Measuring IT.- 1 — Determination of the Number of Bubbles and Their Sizes from the Sound Attenuation Induced by Them.- 2 — Determination of the Free-Gas Content from the Velocity of Sound in a Liquid.- 3 — Investigations of the Free-Gas Content of Liquids.- VII-Crystallization of Metals.- 1 — Mechanism of the Crystallization of Metals in an Ultrasonic Field.- 2 — Ultrasonic Treatment of Steels and Alloys.- 3 — Technological Principles of the Ultrasonic Treatment of a Crystallizing Melt.- VIII - Diffusion in Heterogeneous Systems.- 1 — The Action of Ultrasonic Vibrations on the Diffusion Process.- 2 — Acceleration of Electrochemical Conversions by Ultrasonic Vibrations.- 3 — The Development of an Exposed Photographic Layer in an Ultrasonic Field.- 4 — Crystallization in an Ultrasonic Field.- IX - Acoustic Drying.- 1 — Processes Occurring in a Wet Material during Drying.- 2 - Physical Factors Affecting the Heat- and Mass-Transfer Processes in Sound Fields.- 3 - Influence of a Sound Field on Drying in the First Period.- 4 — Mechanism of the Influence of Sound on Drying in the Second Period.- 5 — Outlook for the Industrial Application of Acoustic Drying.- X - Aerosol Coagulation.- 1 — Types of Aerosol Coagulation.- 2 — Action of a Sound Field on Aerosol Particles.- 3 — Experimental Studies of Acoustic Aerosol Coagulation.- 4 — StreamingMechanism of Particle Interaction in a Sound Field.- 5 — Industrial Applications of Acoustic Aerosol Coagulation.