An industrial furnace for the annealing of aluminum coils was simulated by SIMTEC, in cooperation with ELKEME, the research center of VIOHALCO Group of companies. The coils are produced in various thicknesses and widths, by winding aluminum strips with a cold rolling process. Following the straining of cold rolling, the batch annealing furnaces are employed to heat gradually the coils, to improve the uniformity of the mechanical properties of the metal. The procedure is performed in nitrogen atmosphere, to avoid oxidation due to the elevated temperature. The heat is provided by the exhaust gases of burners, which are circulated in perpendicular U tubes and consequently heat the nitrogen. To prevent the uneven heating of the coils, two horizontally-arranged axial fans recirculate the heated nitrogen. The procedure may last up to a day, depending on the dimensions of the coil.

The goal of ELKEME was to create a library that predicts standard cases of coils’ annealing and thus to enhance the automation and optimization of their production line. SIMTEC developed a CFD model, that calculated heat transfer between nitrogen and aluminum, due to the radiation and the forced convection caused by the fans. The model solved the turbulent flow of nitrogen between the coils, faithfully replicating the changes in revolution speed. The accumulated data were used to create a database, that helped ELKEME to achieve uniformity for the rising temperature, in reduced annealing times.