As a result of the intense air-water interaction in the spray nozzle, air-mist spray is one of the most promising technologies for attaining high heat transfer. CFD simulations and multivariable linear regression were used in the first part of this study to analyze the air-mist spray produced by a flat-fan atomizer and to predict the heat transfer coefficient using the casting operating conditions such as air pressure, water flow rate, cast speed and standoff distance. For the air-mist spray cooling simulation, a four-step simulation method was utilized to capture the turbulent flow and mixing of the two fluids in the nozzle, as well as the generation, transport, and heat transfer of droplets. Analysis of the casting parameters showed that an increase in air pressure results in efficient atomization, increases the kinetic energy of the droplets and produces smaller droplet size thus, the cooling of the slab increases significantly. Also, a decrease in water flow rate, standoff distance and casting speed would result in more efficient cooling of the steel slab. The second part of the study investigated the solidification of steel in the secondary cooling region. Caster geometry and casting parameters were studied to evaluate their impact on the solidification of steel. The parameters studied include roll gap, roll diameter, casting speed and superheat. It was found that a smaller ratio of roll gap to roll diameter is more efficient for adequate solidification of steel without any defect. Casting speed was found to have a significant effect on the solidification of steel while superheat was found to be insignificant in the secondary zone solidification. The result from the air-mist spray cooling was integrated into the solidification model to investigate the solidification of steel in the entire caster and predict the surface temperature, shell growth and metallurgical length. To replicate real casting process, temperature dependent material properties of the steel were evaluated using a thermodynamic software, JMatPro. The air-mist spray model was majorly investigated using ANSYS Fluent 2020R1 CFD tool while the solidification of steel was studied using STARCCM+ CFD software. Using the findings from this study, continuous casting processes and optimization can be improved.

Continuous casting is an important process to transform molten metal into solid. Arrays of spray nozzles are used along the process to remove heat from the slab letting it solidify. Efficient and uniform heat removal without slab cracking is desired during steel continuous casting, and air-mist sprays could help to achieve this goal.Air-mist nozzles are one of the important keys for determining the quality of steel as well as energy consumption for pumping the water. Based on industrial data, it is estimated that a 1% reduction in scrapped production due to casting related defects can result in annual savings of 40.53 million dollars in the U.S. Computational simulations studies can minimize defects in steel such as cracks, inclusions, macro-segregations, porosity, and others, which are closely related to the heat transfer between water droplets and hot slab surface.<div><br></div><div>Conducting multiple spray experiments in order to find optimum operating conditions might be impractical and expensive in some cases. Thus, Computational Fluid Dynamics (CFD) simulation is aimed to be used for simulating the air-mist spray process. Because it is a challenging process due to strong air and water interaction, then numerical models have been developed to simulate water droplets. The first model involves air and water phases which then are transformed in single-phase water droplets. To do so, a Volume of Fraction (VOF) to the Discrete Phase Model (DPM) is used.<br></div><div><br></div><div>VOF-TO-DPM transition model involves the primary and secondary breakup which occurs in the water atomization process, starting with a single water core, followed by a smaller compact mass of water known as lumps or ligaments due to the interaction of air, and finally converted into water droplets.The second model is using the Nukiyama-Tanasawa function size distribution which injects water droplets based on defined size range and velocity profile. A validation of droplet size and velocity against experimental data has been accomplished. The models can avoid acquiring expensive equipment in order to understand nozzle spray performance, and droplets generated. Quality, water droplet velocity, size, energy, and water consumption are the core of the current study. Last but not least, the methodology for this model can be used in any other air-mist nozzle design.<br></div>