Transient boiling heat transfer performances of subcooled water during quenching process

• Transient boiling of subcooled water during quenching process was investigated.
• Outbreak transition boiling curve was analyzed by temperature decrement.
• Nucleate boiling included stable nucleate boiling and transition nucleate boiling.
• Boiling curve of transition nucleate boiling varied with the initial condition.

Transient boiling of subcooled water on a vertical flat surface during quenching process was visually observed using high-speed photography technology and analyzed by special boiling heat transfer models. After the quenching process began, the nucleation was initiated within a short time, and then followed by the outbreak transition boiling with extremely unstable bubbles and sharp heat flux increment which lasted only for about 1 s. According to the boiling curves, the nucleate boiling should be divided into two stages including the stable nucleate boiling and transition nucleate boiling with the effects of initial conditions. The outbreak transition boiling was first studied by special boiling curve corresponding to the temperature decrement, and was further analyzed using a theoretical model based on the combination of the boiling heat flux evolution and lumped parameter assumption. The results showed that the boiling curve of outbreak transition boiling predicted by the theoretical model had a good agreement with experimental data and the heat flux almost had linear relation with the square root of temperature decrement.