HEAT TRANSFER DURING SOLID-LIQUID PHASE TRANSFORMATION OF METALS IN RECTANGULAR CAVITIES
Abstract
Studies of melting and solidification of both pure metal and eutectic alloys in rectangular cavities were undertaken to gain basic understanding of solid-liquid interface motion and provide data on fluid flow and heat transfer. The results from the flow visualization and the temperature measurements in a paraffin system were used as a guide to study buoyancy induced flow structures, convective heat transfer in the melt, and their effect on the shape and the motion of the solid-liquid interface during phase transformation in metal systems. Different flow regimes and structures during phase transformation were deduced indirectly or confirmed from the temperature distribution and the temperature fluctuation measurements, from the solid-liquid interface contours, and from the arrangement of the heat source and the sink. The interface shape was observed and examined by pouring out the liquid phase at a desired time during the phase transformation process. An analytical one-dimensional model, which takes into account natural convection heat transfer in the melt, was developed and the predictions were compared with the measured interface position data from three different materials. Natural convection was found to enhance the melting rate and gradually play an important role in retarding the solidification process. However, during melting or solidification of Lipowitz eutectic the concentration stratification was found to suppress natural convection in the melt. This led to a slower melting rate and a higher solidification rate than the predicted. The melting rate and the time averaged heat transfer coefficients during melting of gallium from the side were measured and correlated.
Degree
Ph.D.
Subject Area
Mechanical engineering
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