Solidification and Melting of Aluminum onto Circular Cylinders Under Forced Convection: Experimental Measurements and Nu
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late nineteenth century, Joseph Stefan formulated the problem of finding the temperature distribution and phase front history of a solidifying slab of water[1] or alternatively in solving a moving boundary problem. Researchers working in the metals processing industry are interested in moving boundary problems as controlling heat transfer and fluid flow at the phase front helps to control the quality of a casting.[2] Those working on the development of front capturing or front tracking algorithms are interested in experimental studies of moving boundary problems to validate their codes.[3] The research presented in this publication is a result of the authors’ ongoing effort to develop invasive high temperature liquid metal velocity sensors that operate on heat transfer principles.[4,5] The measurement of the solidification and melting time (SMT) of aluminum around a cylinder can be used to infer direction of velocity.[4] Also, the shell solidification and melting is an extremely important time in assimilation of additions in liquid metals,[6] representing for some cases at least 90 pct of the entire assimilation time. Studies of assimilation of additions in liquid metals have been carried out exclusively under uniform convective heat transfer conditions. This approach leads to uniform shell solidification and melting around the MITREN SUKHRAM, Graduate Student, and STAVROS A. ARGYROPOULOS, Professor Emeritus, are with the Department of Materials Science & Engineering, University of Toronto, 184 College Street, Toronto, ON M5S 3E4, Canada. Contact e-mail: stavros. [email protected] Manuscript submitted August 29, 2013. Article published online July 29, 2014. METALLURGICAL AND MATERIALS TRANSACTIONS B
addition. However, the potential exists that a uniform shell cannot be formed around the addition. The present work studied this case, with the formation of a nonuniform shell around an immersed object in a liquid metal. As such, it expanded upon the previous investigation of additions in liquid metals[6] by developing a methodology in which the assimilation of additions in liquid metals can be shortened. This work presents experimental data and numerical modeling of the local solidification and melting of aluminum onto circular cylinders under forced convection. The cylinders are solid material that do not undergo solid-to-liquid phase change and are different chemical composition from aluminum. For this moving boundary problem, the solid–liquid interface advances (solidifies) into the liquid and then recedes (melts) toward the solid cylinder over time. A. Literature Review Studies which experimentally track the solid–liquid interface in various material systems under convection are discussed, where techniques to delineate the phase front, the material system, and the type of convection are listed. Hao and Tao[7,8] experimented in a water system, where they tracked the solid–liquid interface under forced and mixed convection during the melting of ice spheres. They observed the melting front of dyed ice spheres visually by
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