Efficient Melt Stirring Induced by the Coupled Effects of Alternating Magnetic Field and Configuration of Cold Crucible
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widely used in the fluid system as it observably affects the transport behaviors. Electromagnetic (EM) stirring enhances the mixing of a fluid,[1] which contributes significantly to the heat and mass transport phenomena,[2] as well as the particle separations from a heterogeneous mixture.[3] By applying alternating magnetic field, the electromagnetic cold crucible (EMCC) is widely used for melting refractory and reactive materials due to its advantages in efficient EM stirring for producing uniform materials.[4] The slits applied to the EMCC are important for EM transparency of the crucible wall, and the induced EM energy in the melt depends strongly on the number and the shape of the slits.[5] Meanwhile, the induction coils surrounding the segmented crucible induce eddy current in each segment, which also could generate an EM field inside the crucible.[6]
YAOHUA YANG, RUIRUN CHEN, JINGJIE GUO, YANQING SU, HONGSHENG DING, HENGZHI FU are with the School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001, China. Contact e-mail: ruirunchen@ hit.edu.cn Manuscript submitted August 30, 2017. METALLURGICAL AND MATERIALS TRANSACTIONS B
Efficient melt stirring during the metallurgy process is always desired, it was found that the rectangular pipe could induce a secondary flow at the cross section, which promotes the mass transfer efficiency during the impurity separation process.[7] Recently, researchers investigated the helical magnetic field (HMF), which can be considered as the superposition of rotating magnetic fields (RMF) and traveling magnetic fields (TMF) and incorporates the advantages of both. The HMF could induce both azimuthal and meridional flow in the melt, which requires less time for achieving the total homogenization of heat and mass in the melt.[8–10] A full understanding of the complex EM stirring of EMCC is beneficial for an efficient and reliable melting process and further for expanded application. EM stirring in the EMCC has been studied by theoretical analysis and numerical simulation in many papers,[11,12] and it is believed that the fluid flow at the vertical section of the melt plays a main role in the convective heat and mass transfer, which is beneficial for improving the homogeneity and purity of melt.[13,14] Until now, lots of investigations on the flow field in the EMCC only focused on the vertical section of the melt, without considering the fluid flow in three-dimension. Therefore, a 3D model was established to understand the fluid flow in greater depth in the EMCC, the coupling effects of the alternating magnetic field and the configuration of the cold crucible were considered. The geometry of the cylindrical EMCC was established using ANSYS (distributed by ANSYS HIT) according to the experimental equipment, as shown in Figure 1. The cylindrical EMCC consists of 8 slits and copper segments, as well as a four-turn coils. For comparison, the induction furnace of ceramic crucible with same dimensions but no slits was built. The EM pressure confines the melt and a meniscus is formed, along wit
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