No abstract

Experimental investigations have been performed for the cooling of hot moving metal sheets of thickness 2 mm and 5 mm with the initial temperature of 500°C to 800°C by two flat spray nozzles. Tap water at room temperature is used as a coolant. Experiments are carried out for nickel, nicrofer, and aluminum alloy AA6082 with varying sheet velocity ( 5,10,15 mm/s) and nozzle inclination angle (45°,65°,90°). The temperature distribution on the backside of the sheet during the cooling is recorded with a high-speed infrared camera. The recorded thermal data are used in the inverse heat conduction analysis to estimate the local heat fluxes and temperatures on the quenched surface. The thermal images obtained are used to analyze the length of the pre-cooling, transition boiling, and nucleate boiling. The maximum heat flux, the DNB temperature, and the rewetting temperature are presented for researched parameters. The nozzle inclination angle has a weak influence. The higher the velocity and the thickness of the sheet are, the higher the maximum heat flux and the shorter the pre-cooling region. The reason is that the position of the max. heat flux is shifted downstream near to impingement region.

Experimental investigations have been performed for the cooling of hot moving metal sheets of thickness 2 mm and 5 mm with the initial temperature of 500 °C to 800 °C by two flat spray nozzles. Tap water at room temperature is used as a coolant. Experiments are carried out for nickel, nicrofer, and aluminum alloy AA6082 with varying sheet velocity( 5,10,15 mm/s) and nozzle inclination angle (45°,65°,90°). The temperature distribution on the backside of the sheet during the cooling is recorded with a high-speed infrared camera. The recorded thermal data are used in the inverse heat conduction analysis to estimate the local heat fluxes and temperatures on the quenched surface. The thermal images obtained are used to analyze the length of the pre-cooling, transition boiling, and nucleate boiling. The maximum heat flux, the DNB temperature, and the rewetting temperature are presented for researched parameters. The nozzle inclination angle has a weak influence. The higher the velocity and the thickness of the sheet are, the higher the maximum heat flux and the shorter the pre-cooling region. The reason is that the position of the max. heat flux is shifted downstream near to impingement region.

The cooling rate of moving aluminum alloy sheets (AA6082) was experimentally investigated. For this purpose, 5mm thick sheets were electrically heated in a furnace to a temperature of 520 ° C and then cooled with water using different nozzle fields. The nozzles were located at a distance of 50 mm from the sheet. A combination of flat and full jet nozzles was used in two different nozzle configurations, each with the nozzles of one type arranged horizontally, resulting in two rows of nozzles. In the first configuration, two nozzles of each type 70 mm distance from each other were used. For the second configuration, three flat jet nozzles and three full jet nozzles, 35mm apart from each other were combined to form a nozzle field. Flat jet nozzles with a jet angle of 45 ° and full jet nozzles with a diameter of 1.05 mm were used. The pressure at the nozzle outlet was kept constant at 2 bar in each case. During the cooling process, the sheet velocity was varied from 5 mm/s to 10 mm/s and the temperature field of the black-coated rear side of it was measured with a high-resolution infrared camera. The high frame rate of 200 fps of the IR camera allows for precise determination of the thermal temporal and spatial data of the sheet. The infrared images and the corresponding cooling curves are qualitatively analysed as a function of the sheet speed and nozzle configuration. The investigation aimed to gain knowledge about the choice of nozzle spacing and the cooling intensity of the nozzle type that results in homogeneous cooling. This study can be used for the optimization of existing plants and the design of new plants.