Generation of void in a molten-metal bath by gas injection from below

An experimental apparatus for investigating the injection of nitrogen gas a nd water into the base of a steel tank containing molten tin has been devel oped A first set of experiments based on only gas injection has been used t o develop a diagnostic technique using continuous high-energy X rays and di gital imaging to observe the mixing process and to measure local and averag e void fractions in the test section as a function of time and space. This unique application of real-time, high-energy, X-ray imaging has been used t o generate two-dimensional mappings of the chordal-average void fraction wi th spatial resolution corresponding to a 0.43-mm(2) cross-sectional area pe rpendicular to the X-ray path and time resolutions of <5 ms. Void fraction measurements with superficial gas injection velocities from 0.07 to 0.14 m/ s into a 0.08-m-deep pool of 683 K molten tin indicate that the time and sp atial average integral void fraction at these gas injection rates is relati vely constant, in the range from 0.26 to 0.31. Similar injections into pool s of 0.14- and 0.15-m depths have also exhibited relatively constant averag e integral void fractions in the range from 0.18 to 0.26 These values are i n good agreement with past integral experimental measurements in mercury, W ood's metal, and molten steel.