Ultra-Fast Transient Pool Boiling under High Pressure and Subcoolings

Growing global energy consumption and demand has led to growing interest in a variety of energy options and new technologies for various applications. A fundamental understanding of the foundational physics is essential in being able to design and safely operate future energy options and technologies. Of particular interest presently are energy sources that produce little to no carbon emissions. Nuclear energy is a vital component of the repertoire of zero-carbon energy sources. Under accident conditions nuclear reactors can undergo high-energy, fast power transients. In addition, advancing technologies are required to dissipate larger quantities of heat at shorter timescales. The goal of this work is to investigate ultra-fast transient pool boiling regimes to enhance the fundamental understanding of this phenomenology and to establish a basis for future energy and technological application. In this work, temperature, heat transfer, and high-speed imagery of transient boiling events are collected during ultra-fast (up to 250,000°C/s) heating pulses to define the behavior and mechanisms occurring. While pool boiling responses have been studied previously at longer time scales, this work provides fundamental understanding of the mechanisms in the ultra-fast timescale. To accomplish this a high-pressure, variable temperature, transient boiling system is created to experimentally study a variety of factors related to ultra-fast transient boiling. These factors include combinations of pressures and water subcoolings, the heater surface condition, the heating shape, and the heating level. The water is heated by, and measurement are taken from, a thin wire inside a pressure vessel. Parameter comparison studies are performed to provide a relative importance of the tested parameters on a variety of experimental outcomes. Additional investigations of the material failure mechanisms under extreme heating rates are presented. Ultimately, this work presents the transient boiling heat transfer and associated phenomena of numerous experimental conditions under ultra-fast heating. This will provide a fundamental evaluation of an area of pool boiling that has not been previously explored. The results can provide a basis to drive growth and future study both in the nuclear industry and in the heat transfer industry, where there is an ever-increasing demand for higher heat transfer and controllable configurations