Micro-Scale Flow Excitation under Imposition of Uniform Magnetic Field and Electrical Current

Abstract

Mass transfer is often the rate-determining step for solid-liquid chemical reactions. Decreasing the concentration boundary layer thickness is essential to intensify the chemical reaction. Because the concentration boundary layer exists in the velocity boundary layer, forcing imposition on the concentration boundary layer by superimposing an electrical current and a magnetic field was proposed. Through this, flow can be directly excited in the concentration boundary layer. The previous results indicate that by superimposing a direct current and a gradient magnetic field, the development of the concentration boundary layer was suppressed because of a macro-scale flow excitation in the whole vessel. By superimposing the gradient magnetic field with a modulated current, the development of the concentration boundary layer was further suppressed. This is because of the macro-scale flow enhancement and the excitation of a micro-scale flow near the solid-liquid interface. However, the mechanism of the micro-scale flow excitation has not been clarified. To clarify this, a uniform magnetic field was superimposed with the direct current or the modulated current. By this means, only the micro-scale flow was excited near the anode surface. The results found that the non-uniform electromagnetic force distribution is the main reason for the micro-scale flow excitation.