The aim of this paper is to characterize two-phase phenomena occurring for a rapid energy discharge in the fluid leading to explosive vapour expansion. This study was motivated by the lack of macro-scale experiments characterizing those transient phenomena at high reduced pressure. For that purpose, a complete test section was designed based on the Joule effect to deliver the energy discharge. ${\text{CO}}_2$ was chosen as working fluid, allowing to work at saturation and under saturation conditions. Equipped with pressure sensors and a high-speed camera, the complete process is recorded during few seconds. The thermal shock in the carbon dioxide creates transient pressure peaks and sudden vapour production. The first observed pressure wave is well described as acoustics. This first wave is followed by a quick (60 ms) generation of vapour.The maximum volume of vapour produced is extracted from pressure fluctuations and matches the theoretical value. Following their creation, the bubbles flow upward in the test section as bubbly flow. Visual observation allows the characterization of the shape and the velocity of pertinent bubbles as part of a wobbling flow. This project, motivated by the so-called Fuel Coolant Interaction (FCI) nuclear safety related problematic, brings consistent data allowing to better characterize the small scale processes for such transient vaporization phenomena. This paper focuses on a single test performed under saturated conditions.

本文的目的是描述流体中快速能量释放导致爆炸性蒸汽膨胀所发生的两相现象。这项研究的动机是缺乏宏观实验来表征那些在高压下的瞬态现象。为此，基于焦耳效应设计了一个完整的测试部分来提供能量放电。${\text{二氧化碳}}_2$被选为工作流体，允许在饱和和饱和条件下工作。配备压力传感器和高速摄像头，整个过程在几秒钟内被记录下来。二氧化碳中的热冲击会产生瞬时压力峰值和突然产生的蒸汽。第一个观察到的压力波被很好地描述为声学。第一波之后是快速（60 毫秒）产生的蒸汽。产生的最大蒸汽量是从压力波动中提取的，与理论值相匹配。在它们产生之后，气泡在测试部分作为气泡流向上流动。目视观察可以表征相关气泡的形状和速度，作为摆动流的一部分。这个项目，受所谓的燃料冷却剂相互作用 (FCI) 核安全相关问题的推动，带来了一致的数据，可以更好地表征这种瞬态汽化现象的小规模过程。本文重点介绍在饱和条件下进行的单一测试。