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Abstract

The low-pressure die casting (LPDC) process is widely used to manufacture aluminum alloy wheels and other rotationally symmetric components. Effective thermal management of the die is essential to control solidification and avoid casting defects. Water-cooled channels embedded in the die play a key role in heat extraction, yet their design is often based on trial and error knowledge due to limited fundamental understanding of boiling behavior under transient cooling conditions. This research investigates the evolution of boiling heat transfer regimes in water-cooled steel channels under LPDC-relevant conditions. A lab-scale experimental system was developed using a heated H13 steel block with internal water channels and subsurface thermocouples to measure transient temperature histories. The recorded data were analyzed using an inverse heat conduction (IHC) algorithm to determine surface heat transfer coefficients (HTCs) as a function of time and temperature. The resulting boiling curves reveal four distinct regimes: an initial unsteady boiling region, a partial subcooled boiling regime dominated by nucleate boiling, a transition boiling region, and a single-phase convection regime. The partial boiling region was identified as the most effective for heat extraction, with its behavior strongly influenced by flow rate, initial die temperature, coolant temperature, and flow duration. Empirical correlations were developed for each heat transfer regime, including a modified Dittus–Boelter equation for the single-phase region. These correlations were implemented in a forward thermal model to assess their predictive capability. The model demonstrated strong agreement with experimental measurements across a range of cooling scenarios, including steady-state and interrupted flow conditions.