Steam Explosions of Single Drops of Molten Silicon-Rich Alloys
Commercial quantities of ferrosilicon alloys and silicon metal in the form of granules are available. They are produced in water granulation, a process involving the risk of large-scale steam explosions. To learn about these steam explosions, we have investigated single drops of molten alloys when released into water. When single drops of molten ferrosilicon alloy with 75 wt.% Si (FeSi75) or silicon metal at its liquidus or melting temperature were released into cold, room temperature or hot water, spontaneous explosions never occurred. We could, however, initiate steam explosions by exposing the drops to upwarddirected pressure transients generated in the water with an encapsulated impactor. For water at room temperature, we determined (a) the strength of the pressure transients needed to initiate the steam explosion of a single drop, and (b) the range of fall depths over which the drop can be triggered to explode with this transient. When varying the water temperature we learned that the triggered explosions became less vigorous as the temperature increased. The explosions became more vigorous also when the Al and/or Ca content in the molten drop decreased. Photographic images of the bubbles generated during the steam explosions indicate that the maximum energies released correspond to about 1 % to 2% (dependent on drop size) of the total enthalpy of the molten ferrosilicon at its liquidus temperature. During the explosions, tiny bubbles of a permanent gas, presumably hydrogen, were generated. Video images show that ferrosilicon drops with diameters between 3 mm and 11 mm fall through water at about 0.5 m/s. Shutter wheel photographs confirm these fall rates and also indicate the onset of solidification of the drops and show that steam explosions can occur in partially solidified drops.
An Experimental Study of Small-scale Vapor Explosions for Molten Tin Dropped into Water
A series of experiments were carried out for small-scale vapor explosions in a "dropping" system using molten tin and water. Experimental parameters such as initial tin temperature, water temperature, ambient pressure and sample size of tin were varied over a wide range. The pressure of explosion, the rate of occurrence of explosion and the position of explosion were measured in detail. It is found that tough the vapor explosion has in general statistical characters, a delay time between tin-water first contact and explosion increases systematically with both water temperature and initial tin temperature. As a resul, it is concluded that the vapor explosion is closely related to transient boiling phenomenon, especially to the collapse of a stable vapor film around the molten metal.
Church, state and schools in Britain, 1800-1970
Originally published 1971, this volume unravels the complicated history of the religious question in British education. The background of the key Acts of Parliament which established the "dual" system - of Church and Local Authority school - is examined. The changing policies of different religious groupings are analyzed, and their outcome in legislation brought out.