Visualization of heat and mass transfer near the formation and dissociation interface of CO2 hydrate with high-speed phase-shifting interferometer

In this study, transient heat and mass transfer during CO2 hydrate formation and dissociation processes is visualized quantitatively by a high-speed phase-shifting interferometer. CO2 hydrate has an attractive potential to be used as CO2 capture and storage (CCS) and secondary refrigerant due to the enormous dissociation enthalpy. However, gas hydrate dissociation mechanism including CO2 hydrate has not been well understood due to the complex phase-change and heat and mass transportation at the reaction interface. This study aims to measure CO2 hydrate formation and dissociation process with transient heat and mass transfer in the vicinity of solid-gas interface quantitatively. CO2 hydrate is formed on a liquid film with the pressurized CO2 gas. The experiment is conducted in the temperature controlled pressure vessel with two quartz windows. The dissociation is caused by decreasing the pressure. The transient density distribution in the vicinity of solid-gas interface during the formation and dissociation is measured quantitatively by using the high-speed phase-shifting interferometer. The simulation is performed with the two-dimensional (2D) diffusive equation in the gas phases to validate experimental results. Finally, the CO2 mass concentration and the effect of heat transfer in the gas phase on the formation and dissociation are discussed.