Bath Volume Effects on Large-Scale Steel Quenching Performance: Conjugate Heat Transfer Modeling and Frequency Analysis of Flow-Induced Thermal Non-uniformities

Industrial quenching operations represent a critical thermal management process in steel manufacturing, where precise control of cooling rates directly impacts material properties, energy efficiency, and production consistency. This study investigates the thermal behavior and cooling non-uniformities occurring during the quenching of large steel blocks weighing up to 20 tons, with the aim of establishing quantitative design guidelines for enhancing industrial quench bath systems. Experimental temperature measurements obtained from multiple thermocouples revealed significant thermal gradients across an instrumented block, highlighting the influence of flow dynamics on cooling performance. Near-surface locations exhibited rapid cooling rates of approximately 3 to 4 °C/s, while internal positions 150 mm beneath the surface experienced rates as low as 0.25 °C/s. A coupled multiphysical conjugate heat transfer CFD model was developed to capture the dominant phenomena governing the quench process, accounting for turbulent liquid-vapor flow interactions and temperature-dependent thermophysical properties, achieving a normalized root mean square error (NRMSE) of 2.56 pct on average. The validated model was employed to assess the influence of bath water volume on cooling efficiency and temperature uniformity, evaluating configurations ranging from a reference volume of 70 to 80, 90, and 100 m³. Despite substantial increases in water mass, improvements in cooling rapidity were minimal, and larger bath volumes did not proportionally enhance heat extraction efficiency. Frequency spectra and turbulence kinetic energy analyses revealed that additional water mass modifies local flow structures, generating new vortical zones and damping turbulence mechanisms directly responsible for the diminishing thermal performance gains. A bath volume of 90 m³ was identified as the most energy-effective configuration, balancing cooling performance with resource utilization. These findings provide practical engineering guidance for the design and enhancement of industrial quenching systems, contributing to improved thermal management, reduced energy waste, and more consistent product quality in large-scale steel manufacturing.