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Rapid depressurization and phase transition of CO2 in vertical ducts – Small-scale experiments and Rankine-Hugoniot analyses

Author:
Hansen, Per Morten, Gaathaug, André Vagner, Bjerketvedt, Dag, Vaagsaether, Knut
Source:
Journal of hazardous materials 2019 v.365 pp. 16-25
ISSN:
0304-3894
Subject:
boiling, carbon dioxide, diaphragm, energy, evaporation, explosions, liquids, models, vapors
Abstract:
This study discusses the rapid expansion and phase transition of liquefied carbon dioxide (CO2) in vertical ducts. Results from small-scale experiments in three test setups (A, B, and C) were compared with a Rankine-Hugoniot model that treats the phase transition as an adiabatic evaporation wave of constant thickness. The model calculates the fluid properties behind the evaporation wave. The motivation was to identify hazards and quantify the energy-release in tank explosions such as a boiling liquid expanding vapor explosion. The experimental results corresponded with a Chapman Jouguet (CJ) solution. The contributions include a mapping of CJ solutions calculated from a range of pre-rupture conditions. The puncture of a diaphragm (setup A, and B), or complete test section rupture (setup C) initiated the tests. The three test setups provided a range of pressures for the model. Evaporation waves were observed, propagating with velocities of 35–42 ms−1 (setup A, and B), and ∼ 10 ms−1 (setup C) into the superheated liquid. The calculated vapor mass fraction behind of the evaporation wave was in the range 0.21-0.23. The study presents a strategy, which incorporates the calculated vapor mass fraction, to predict the energy released in a tank explosion.