Multiphase numerical modeling of boiling flow and heat transfer for liquid jet quenching of a moving metal plate

Quenching by means of liquid jets is an extensively applied heat treatment process in metal industries for the intensive cooling of a metal plate or sheet for attaining specific material properties by controlling the thermal history. During the intensive cooling process, the spatial and temporal heat transfer behavior of the metal plate highly influences the microstructure development and thereby the material hardness and properties. Heat treatment process involves heating the metal to a high temperature followed by liquid jet quenching. Due to the high surface temperature, the boiling heat transfer regimes dominate over the surface, where distinct regimes such as film boiling, transition boiling, nucleate boiling as well as the pure convective heat transfer occur simultaneously resulting in immense temperature gradients. Moreover, the Leidenfrost effect adversely affects the heat transfer from the surface by virtue of strong vapor generation. This varying cooling curves may result in residual thermal stresses and cause deformation and crack formation. Furthermore, in industrial applications such as hot rolling, chill casting etc., the metallic specimen is moving below the stationary jet during the cooling process which significantly influences the heat transfer. Therefore, in order to secure the targeted quality together with reducing the potential of distortion and crack formation along with an efficient energy and resource utilization, a profound investigation into this conjugate heat transfer process of a moving plate is indispensable. Considering the complexity of the process and the technical obstacles, investigating this process by means of experiments is limited. To properly address this process, a multiphase numerical model based on Euler-Euler approach is developed for investigating the hydrodynamic as well as the thermodynamic characteristics in all boiling phases during quenching. In this model, water acts as continuous phase and vapor as dispersed phase where the movement of the plate is incorporated with the sliding mesh concept. In this novel approach, the numerical model allows the analysis of a moving metal plate quenching with a single full jet. For model validation, experiments are conducted in which an aluminum alloy (AA6082) plate is quenched with normal tap water. The validated numerical model can investigate the heat flux, HTC (heat transfer coefficient), wetting front behavior etc. The influence of jet Reynolds number, plate velocity and plate materials (Al-alloy AA6082, St-steel 1.4828) during the process are numerically analyzed.