Heat Transfer Study of Continuous Casting Second Cooling Based on Simulation of Nozzle Jet Flow

During continuous casting, the non-uniform cooling of cast billets is closely associated with the jet behavior of nozzles. This study focuses on a full-cone water nozzle used for continuous casting at a steel plant. A multiscale simulation model, validated through multidimensional experiments, for nozzle jet atomization is established by coupling the Volume of Fluid to Discrete Phase Model (VOF-to-DPM) with adaptive mesh refinement technology. Numerical modeling and physical experiments analyzes the atomization process of nozzle jets, variation laws of droplet parameters, effects of atomized droplets on the vapor film penetration, and heat transfer performance on the billet surface under different operating conditions. The results indicate that both the average droplet velocity and diameter decrease gradually with increasing spray height. The proportion of droplets penetrating the vapor film decreases significantly with an increase in radial distance. Reduced droplet penetration shifts the cooling pattern of the cast billet from transitional boiling to pure film boiling, which impairs the heat transfer efficiency of the nozzle. The heat transfer performance of droplet impingement on high-temperature cast billets under various operating conditions is assessed by analyzing the heat transfer process of individual droplet impingements. Therefore, a calculation model for the nozzle heat transfer coefficient (HTC) considering the mass fraction of droplet penetration is established. A solidification heat transfer model was developed and compared with on-site infrared temperature measurement results. This calculation model can better reflect the actual heat transfer effect of continuous casting billets, thereby providing theoretical and technical support for accurately establishing a mathematical model of continuous casting secondary cooling heat transfer and optimizing nozzle layout.