Effects of Reynolds number and translation speed on flow and heat transfer for aluminum sheet processed in an air-cushion furnace

Abstract

In present study, the heat treatment of an aluminum sheet in the air-cushion furnace is simulated. The sheet is 0.6 mm in thickness and suspended under the action of jet impingement. Effects of Reynolds number and the sheet-jet velocity ratio on flow, heat transfer and structural property of the sheet are investigated. At low Reynolds number, the sheet sinks at its middle part. With increasing Reynolds number, upward bending arises, and the circulating flows between the sheet and the nozzles are intensified, and peaks of Nusselt number are more protruding. At low sheet-jet velocity ratio, the middle part of the sheet is dominated by severe deformation, and overheating is induced at the right end of the sheet. With increasing sheet-jet velocity ratio, the symmetry of flow structures in the nozzle unit is degraded, and heat transfer is enhanced. An optimum combination of Reynolds number of 10,000 and a sheet-jet velocity ratio of 0.1 is eventually obtained.