New insight into investigation of thermal transfer of molten steel inside a ladle with vacuum shell

Abstract

In order to reduce the amount of thermal loss of steel inside a ladle during the industrial production, one new type ladle constructed using radiation-proof steel plates welded on the exterior walls of conventional ladle and its lid was investigated. Thermal insulation principle of vacuum is applied to study the mechanism of thermal transfer, and a novel approach is proposed for calculation of comprehensive thermal conductivity inside the vacuum chamber. The main idea of this paper was to explore the effects of pressures inside vacuum chamber on the temperature of molten steel. The conclusions were made. When the absolute pressure inside the chamber of the ladle is set to 50 Pa, as with its lid, the temperature drop of molten steel is a mere 9 K; while the chamber of the ladle is set to 105 Pa, as with its lid, the temperature drop is 37 K and heat flux occupies the minimum proportion value, 15.38 %. Thermal conduction ability of air molecule is almost not affected by pressure. The additional conversion convection factor value at 104 Pa is 200 times larger than that at 50 Pa. The ability of comprehensive thermal conduction is poor due to low pressures and small amount of air molecules. Thermal conductivity of refractory layer is 11 times larger than that of vacuum layer at 50 Pa. Thus, vacuum layer has strong thermal insulation at lower vacuum pressures.