Experimental study of a thermal shock in carbon dioxide

This PhD work focuses on the thermal shock during the contact between a hot solid and colder fluid. Intense heat transfers from the solid to the liquid could generate strong mechanical response due to the expansion of the fluid and its vaporization. For nuclear power plants safety studies, such thermal shock could be encountered during the hypothetical release of fuel within coolant during a so-called reactivity induced accident. In this work the experimental and theoretical study of such thermal interaction is considered through a specific test section. This test section permits to transfer a high amount of energy (500 J) toward pressurized liquid carbon dioxide in a small amount of time (5 ms). The experiments performed revealed how pressure transients are related to the vapour creation and dynamics. Such transient has been modelled by a differential equation which compares the dynamics of the vapour growth and the dynamics of pressure increase in the vapour at constant volume. Following the first pressure transient, a massive generation of vapour has been observed, as well as a characteristic bubbly flow. A large number of experiments has been performed over a wide range of test conditions. These conditions allowed varying the energy deposited in the fluid and its properties that has been expressed thanks to three non-dimensional numbers. The intensity variations of the resulting thermal shock phenomena have been studied thanks to these non-dimensional numbers. (author)