Numerical study on stirring of large silicon melts by Carousel magnetic fields

A novel electro-magnetic stirring approach using Carousel magnetic fields (CMF) generated by bottom multifunctional KRISTMAG (R) heater magnets is proposed for directional solidification of large silicon ingots for photovoltaics (PV) with mass of 700 kg. 3D numerical simulations were performed for Reynolds, Rayleigh and magnetic Taylor numbers in the range from Re=7.044 x 10(3)-2.123 x 10(4), Ra=2.0083 x 10(9)-2.0096 x 10(9) and Ta-mag=5.26 x 10(9)-3.79 x 10(10), respectively. Stirring progress was studied by tracking the volume average velocity, vorticity and temperature in the melt using buoyancy driven flow as a benchmark. The numerical results show advantageous enhanced mixing by CMF even along the melt cross section parallel to the solidification front and axial flow intensification parallel to the growth direction, particularly in the bottom melt region without dangerous acceleration of the flow in the vicinity of the crucible side walls. (C) 2012 Elsevier B.V. All rights reserved.