Decrease of Concentration Boundary Layer Thickness by Using Vibrating Electromagnetic Force

For clarification of vibrating electromagnetic force effect on concentration boundary layer thickness formed near solid–liquid interface, a metal copper working as an anodic electrode was dissolved into an electrolyte aqueous solution under the imposition of a vibrating electromagnetic force. For its excitation, a current composed of DC and AC components and a static magnetic field were simultaneously imposed on an electrolyte aqueous solution. Because the copper divalent ions concentration is related with brightness of the solution by Lambert–Beer law, brightness of the recorded data using a video camera was directly used for evaluation of the concentration boundary layer thickness formed near the anodic electrode. The concentration boundary layer thicknesses formed under the imposition of the DC current and the static magnetic field, under the imposition of the DC & AC superimposing current without a static magnetic field, and under the imposition of the DC current without a static magnetic field were almost the same, while that formed under the imposition of the DC & AC superimposing current and the static magnetic field was thinner in comparison with the other three conditions. Hydrodynamic instability induced by the vibrating electromagnetic force through a large velocity gradient when the DC & AC superimposing current and the static magnetic field were imposed on the solution might be the reason of the thinner concentration boundary layer. This might be a new tool for controlling mass transfer rate in a concentration boundary layer. [doi:10.2320/jinstmet.J2017022]