Contactless Mixing of Liquid Metals
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se viscous fluids is a common operation in many branches of processing industries, e.g., chemical, biochemical, metallurgy, and crystal growth. With growing interest in Moon exploration and an increasing rate of technological applications used in space, e.g., on the International Space Station (ISS)—which includes crystal growth,[1–4]—the problem of melts mixing under microgravity conditions is becoming more relevant for industrial applications than it was 10 or 20 years ago. The use of convenient mechanical agitators, such as static mixers[5] or rotating impellers in coaxial mixers,[6] in space is a technically demanding problem. For electroconductive liquid materials, an alternative to the conventional schemes mentioned is contactless electromagnetic stirring (EMS). EMS is based on the application of alternating magnetic P.A. NIKRITYUK, Group Leader, is with the CIC Virtuhcon, Institute of Energy Processes and Chemical Engineering, Technische Universita¨t Bergakademie Freiberg, Reiche Zeche/Fuchsmu¨hlenweg 9, 09596 Freiberg, Germany. Contact e-mail: Petr.Nikrityuk@ vtc.tu-freiberg.de K. ECKERT, Group Leader, is with the Chair of Magnetofluiddynamics, Institute of Fluid Dynamics, Technische Universita¨t Dresden, Mommsenstr. 13, 01062 Dresden, Germany. R. GRUNDMANN, Professor, is with the Institute for Aerospace Engineering, Technische Universita¨t Dresden, Mommsenstr. 13, 01062 Dresden, Germany. Manuscript Submitted March 27, 2009. Article published online December 3, 2009. 94—VOLUME 41B, FEBRUARY 2010
fields to induce a motion in the melt. This type of stirring became popular by the mid-1970s in the steel industry[7] because of the simple equipment design, which for rotary stirring with a rotating magnetic field (RMF), is the same as that of nearly all modern electric motors. An alternative to rotary stirring is the axial or ‘‘up and down’’ version of stirring, which provides a liquid movement in a direction parallel to the cavity axis. This type of flow is induced by a traveling magnetic field (TMF), which is generated by a linear motor. RMF and TMF fields are used widely for experimental studies of the influence a liquid phase motion has on heat and mass transfer during crystal growth[2,8–10,11] and solidification of metal alloys.[3,4,12] In such experiments, it is necessary that all alloy components are distributed homogeneously in the melt. To achieve this distribution, it is important to know both the main mechanism responsible for the mixing as well as the time needed to homogenize the liquid phase. Despite the fairly advanced theoretical and experimental studies of the conventional mixing processes,[13,14] works devoted to the mixing of multicomponent electroconductive media by alternating magnetic fields, such as RMF and TMF, are scarce. In particular, we are aware of only Gelfgat et al.,[1,15] Stiller and Koal,[16] and Cramer et al.,[17] who carried out numerical and experimental studies of the impact of RMF and TMF and their continuous superposition (CS) on isothermal flow in terms of mixing efficiency. In particular
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