Evaporation phase transition dynamic process of liquid CO2 driven by compound heat transfer in storage tanks for mine fire prevention: A theoretical model and experimental studies

Mining liquid CO 2 (L-CO 2 ) storage tanks are vulnerable to external high temperatures and deep geothermal during storage and transportation. The heat is transferred from the outer wall of the storage tank to the interior due to compound heat transfer effects. This ultimately results in the evaporation phase transition of the L-CO 2 inside the tank. The process causes the CO 2 to escape into the air, which increases the risk of asphyxiation in confined spaces for miners and dry ice freeze plugging. Therefore, it is necessary to investigate the evaporation phase transition dynamic process driven by compound heat transfer. In this study, an evaporation phase transition model of L-CO 2 was established based on heat transfer theory and CO 2 phase transition theory. Concurrently, seven types of physical simulation experiments of the evaporation phase transition dynamic process with different schemes were carried out, based on an experimental system for the evaporation phase transition of L-CO 2 that was constructed independently. The influence of ambient temperature and initial filling ratios was considered in the experimental study. On this basis, the relative errors of the theoretical calculation values and experimental data were discussed, and then the accuracy of the evaporation phase transition model was validated. The result indicates that increasing ambient temperature leads to faster rises in temperature and pressure within the L-CO 2 storage tank and extends the evaporation phase transition duration. The initial filling ratio primarily affects the initial storage period. Tanks with a lower initial filling ratio exhibit a more intense evaporation phase transition initially but with a shorter duration. The research results have vital theoretical guiding significance for scientific design and residual quantity prediction of mine L-CO 2 storage tanks. • A novel physical model for L-CO 2 evaporation phase transition in the storage tank was established. • The evaporation-induced mass loss rate per minute in the storage tank was accurately quantified. • The phase transition process of liquid CO 2 evaporation is subdivided into three stages • The influence of ambient temperature on the storage tank is significant, and the influence of the initial filling rate is concentrated in the early stage of storage.