A Computationally Efficient 3D Mathematical Model of a Molybdenum Batch-Reheating Furnace ⁎ ⁎This research work has been performed in the EU project Power Semiconductor and Electronics Manufacturing 4.0 (SemI40), which is funded by the programme Electronic Component Systems for European Leadership (ECSEL) Joint Undertaking (grant agreement no. 692466) and the programme “IKT der Zukunft” (project no. 853343) of the Austrian Ministry for Transport, Innovation and Technology (bmvit) between May 2016 and April 2019. More information on IKT der Zukunft can be found at https://iktderzukunft.at/en/. Moreover, the project SemI40 is co-funded by grants from Germany, Italy France, and Portugal. , ⁎⁎ ⁎⁎The financial support by the Austrian Federal Ministry for Digital, Business and Enterprise, and the National Foundation for Research, Technology and Development, and voestalpine Stahl GmbH is gratefully acknowledged.