EXPERIMENTAL INVESTIGATION OF TRANSIENT TEMPERATURE DISTRIBUTION AND HEAT TRANSFER BY JET IMPINGEMENT IN GLASS TEMPERING PROCESSING

Heating and sudden cooling are among the most important processes affecting temper quality in the production period of tempered auto glass. In this study, heat transfer characteristics and cooling times during the sudden cooling process of tempered glass production have been experimentally investigated. Flat glass with dimensions of 50x50x4 mm has been heated up to 680 degrees C in the furnace and was then exposed to sudden cooling process until its surface temperature dropped to 70 degrees C. In the cooling process two mutually placed 8 cm long air jet nozzles with an internal diameter of 8 mm have been used. Experiments have been conducted for Reynolds numbers in the range of (20000 <= Re <= 40000) and for dimensionless jet to plate distances in the range of (1 <= H/D <= 10). Based on the above parameters cooling periods, local (Nu(x)), average (Nu(aver)) and stagnation point (Nu(stad))Nusselt numbers have been experimentally determined.