Improvement on Temperature Uniformity in an Industrial Tip-up Heat Treating Furnace

Temperature uniformity in furnaces is highly important in industrial heat treating processes. Tip-up furnaces are commonly used in heat treating operations for example in austenitizing, tempering, normalizing, etc.  Nowadays these furnaces are required by the heating process to accomplish very narrow levels of temperature uniformities. One way tip-up furnaces do this is by eliminating heat losses through door seals by having the entire furnace bottom seal against fiber or a sand seal box. Nonetheless, ways of improving temperature uniformity are always searched for. Having excess air through burners is one way of improving temperature uniformity. Although this method is somehow effective at homogenizing temperatures within the furnace, it is also intensive in fuel consumption. Pulse firing methods are a good alternative to improve temperature uniformity while minimizing fuel consumption.

In this work different furnace designs are explored via computational fluid dynamics analysis. A benchmark simulation is compared with temperature uniformity survey data obtained from an industrial furnace in operation. The agreement between simulations and experiments was good. This study investigates the influence of the number of burners and exhaust flues and their position in the temperature uniformity. In addition, the geometry of the internal volume was also studied. It was found that all variables studied had an important impact in temperature uniformity, however modifying the internal volume of the furnace was found to be the simplest solution with the best results. The optimized design was implemented in an industrial tip-up furnace. Temperature uniformity improved from a class 3 furnace to a class 1 (+/-8°C to +/- 3°C). These results show that computational fluid dynamics is an effective tool for furnace design and optimization.