Modelling of the cooling process of steel tubes in a rake type cooling bed

Despite the fact that production speed in a hot tube rolling facility is highly dependent on effective cooling of the output product, the mechanisms of the heat transfer in cooling beds are only addressed in few experimental and numerical studies. As a result, industry calls for a mathematical model, which is capable of predicting heat transfer rates and temperatures for the transient cooling process of steel tubes in a rake type cooling bed. Compared to current state-of-the-art approaches, the present work takes a major modification into account: Horizontal spacing between the tubes, S _h/D, was identified as having a significant impact on the heat transfer. Its influence on natural convection and radiation was investigated in CFD simulations on a horizontal cylinder array for Rayleigh numbers in the range of 10 ⁴⩽Ra⩽10 ⁸. Based on the results of the numerical investigation, correction functions for the heat transfer in existing correlation equations were introduced. In the range of 1.25⩽S _h/D⩽3.0, convective heat transfer in the tube array increases by up to 9.91% compared to an individual tube, while heat transfer due to radiation decreases by up to 25.39%.