Visualization of dynamic phase mixing and equilibrium process in transcritical and supercritical conditions

Abstract

The phase mixing and equilibrium process plays a crucial role in the energy cycle and fuel process of supercritical fluids. This study focuses on the dynamic phase mixing during equilibrium process. The transient high-precision measurement of the density field during the phase mixing and equilibrium process is realized by the phase-shifting interferometer based on the pixelated-array masked method. The slow density equilibrium between four typical phase transition routes is captured and quantified with the visualization images and local parameters. The interface spreading rate during the equilibrium between liquid and supercritical is at a rather high level as 0.82 mm/s on average. This phenomenon is controlled by mixing and diffusion, which are faster process than evaporation. Nevertheless, equilibrium can be retarded even in a supercritical environment during the phase mixing between liquid-like and gas-like crossing the pseudo-critical line (average value of interface spreading rate as 0.45 mm/s), where there is a significant density gradient that generates a “solid wall” (buffer layer) effect.