Cold Model Investigations of Melting of Ice in a Gas-Stirred Vessel
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INTRODUCTION
COLD-MODEL and hot-model investigations have been performed by several researchers in the past to estimate heat and mass transfer phenomena during the melting process.[1–23] The idea to investigate the melting process by using the ice-water model is also not a new one. Taniguchi et al.[4] conducted cold-model and hotmodel studies to study the effect of gas injection on the melting rate of solid spheres. For the hot-model investigations, aluminum with different silicon compositions were used and heat transfer and mass transfer coefficients were obtained by using dimensionless correlations for free and forced convection. Iguchi et al.[5] used an ice-water model to represent the dissolution of solid in the steel bath. The melting process of a rectangular ice prism immersed in bubbling jet in a cylindrical vessel was investigated. However, as a simplification the heat transfer coefficient was estimated by using an equation for the sphere. In another investigation, they measured velocity and turbulence around a sphere (made of synthetic resin) submerged in water and contained in a cylindrical vessel with the provision of bottom blowing. Laser Doppler Velocimeter (LDV) was used to measure velocity profiles. The melting of spherical shaped ice samples was recorded by video camera. An empirical expression for the Nusselt number was proposed as a function of the Reynolds number and turbulence intensity. Predictions were also made for the complete melting time of ice. Kurobe and Iguchi[6] AJAY KUMAR SHUKLA, Ph.D Student, and BRAHMA DEO, Professor, are with the Department of Materials Science and Engineering, Indian Institute of Technology, Kanpur 208016, India. Contact e-mail: [email protected]. RYABOV DMITRY, Ph.D Student, OLENA VOLKOVA, Post-Doctoral Fellow, and PIOTR R. SCHELLER, Director and Professor, are with the Institute of Iron and Steel Technology, Technical University Bergakademie, Freiberg, Leipziger Straße 34, 09596 Freiberg, Germany. Manuscript submitted August 31, 2010. Article published online December 3, 2010. 224—VOLUME 42B, FEBRUARY 2011
investigated the melting process of a Zn ingot immersed in a continuous hot-dip plating bath by using an ice prism and a transparent vessel (cold model) made on a reduced geometrical scale of one-tenth. The Nu number was used as similarity criteria. The mean heat transfer coefficient, calculated by averaging the local heat transfer coefficients over the entire surface of the ice prism, was only weakly dependent on the turbulence intensity, for the range of Reynolds number considered. The value of the heat transfer coefficient calculated from the Whitaker’s empirical equation was within 15 pct of the measured value. Wright[7] studied the dissolution rates of commercial black iron rods in iron/carbon melts under isothermal conditions. The effect of melt carbon content, temperature, natural convection, and gasstirred forced convection conditions were investigated and correlations were derived. As expected, the mass transfer coefficient was found to be dependent on the gas flow rat
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