An experimental investigation of rapid boiling of CO2

Abstract

Storage of pressurized liquified gases is a growing safety concern in many industries. Knowledge of the thermodynamics and kinetics involved in the rapid depressurization and evaporation of such substances is key to the design and implementation of effective safety measures in storage and transportation situations. In the present study, experiments on the rapid depressurization of liquid CO2 are conducted in a vertical transparent shock tube which enables the observation of evaporation waves and other structures. The depressurization was initiated by puncturing a membrane in one end of the tube. The thermodynamic mechanisms that govern the evaporation process are not unique to CO2, and the same principles can be applied to any liquified gas. The experiments were photographed by a high-speed camera. Evaporation waves propagating into the liquid were observed, traveling at a near constant velocity on the order of 20??0 m/s. A contact surface between the vapor and the liquid-vapor mixture was also observed, accelerating out of the tube. Pressure readings in the tube suggest that the evaporation wave could be similar to a spinodal decomposition wave, but further experiments are needed to confirm this. When the membrane was in direct contact with the liquified CO2, some indications of homogeneous nucleation were observed.