Experimental studies on drop formation at the tip of melting rods
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I.
INTRODUCTION
THE phenomenon of drop formation at capillary tips has been fairly well understood.~ Recently, drop formation at conical tips until the onset of instability has also been analyzed. 2'3 However, drop formation at the tip of melting rods will be of more interest to metallurgists. There have been very few citations which deal with this aspect, 4-9 the most significant among which is the work of Campbell. 9 Although the reported preliminary experimental results have identified certain parameters influencing the drop size, there seems to have been no rigorous analysis to quantify such influence. The experimental investigation presented in this communication attempts to study the effect of melting phenomenon on drop formation and to look for similarity with drop formation at conical tips. II.
EXPERIMENTAL
Paraffin wax was used as the material for melting studies in the hot bath of ethyl alcohol/acetonitrile liquid, which enabled direct visualization of the melting phenomenon. A schematic sketch of the experimental set-up is shown in Figure 1, the details of which have been described elsewhere. 10Machined wax specimens of the desired diameter, height, and conical tip were firmly fixed to a wooden rod of the same diameter, using a thin coating of araldite, and the wooden rod partially immersed inside the hot liquid. This arrangement was to overcome the necking phenomenon observed in partially immersed wax rods. ~~ The bath was maintained at the desired operating temperature within ---1 ~ The temperature gradient in the hot liquid bath was not more than 1 ~ The drop formation was followed through movie-photography using a Pailard Bolex camera. When the required number of drops were formed, the experiment was arrested by pulling away the specimen. The solidified drops were collected below, dried, and weighed to obtain the drop mass.
S. RAMESH BABU, formerly Senior Research Fellow with the Department of Metallurgy, Indian Institute of Science, Bangalore 560 012, India, is a Visiting Researcher in the Department of Metallurgy, North East University of Technology, Shenyang, People's Republic of China. Manuscript submitted September 17, 1985. METALLURGICALTRANSACTIONS B
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RESULTS AND DISCUSSION
A. Visual Observations As the drop grows to full size, it enters the instability stage characterized by the formation of a neck. The rapidly deforming long neck of liquid connecting the detached drop and the residual drop was observed to form a satellite droplet during detachment, similar to Campbell's observation. 9 The mass of the droplet, being often less than 0.5 pct of the main drop, was neglected in the determination of drop mass. While the specimens machined from red cored wax rods were melting, the path of the red color wax entering from the central portion into the forming drop was visually followed to study the effect of melting rate on possible internal circulation. However, up to the maximum operating melting rate condition of - 3 gm/min, no appreciable internal circulation was observed in either the
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