Coupled CFD simulation for the cooling process of steel tubes in a rake type cooling bed

In the past, cooling beds in hot tube rolling mills were constructed with mixed convection zones at the inlet of the bed. This caused high thermal strains, which resulted in deformed tube geometries. To find the optimal position for a mixed convection zone, the present work introduces the first full-scale CFD simulation of the transient cooling process of tubes in a rake type cooling bed. The model represents a novelty in this process, with one significant improvement to current state-of-the-art approaches: Translatory and rotatory movement of the tubes was simulated with an iterative steady-state/transient coupled method with high accuracy and minor computational cost. Simulations were carried in 2D and 3D and a comprehensive comparison regarding the precision of the method was presented. Among the evaluated quantities were the cooling rates, radial and axial tube temperature distributions as well as heat transfer rates and Rayleigh numbers. For the investigated ensemble of tube geometries, tube temperatures were predicted within 9.23% of the experimental data in the 2D model and 5.42% in the 3D model.