Measurement and visualization of supercritical CO2 in dynamic phase transition

Abstract

A new experimental device was developed to observe and measure dynamical generations of supercritical CO2 in a chamber. Temperature and pressure were measured locally by thin thermocouple and pressure transducer. The Rayleigh scattering in the chamber was visualized by a high-speed video camera. Heating of the liquid CO2 was conducted by a ceramic heater from the upper or the lower side of the chamber. In the case of heating from the upper side, temperature profile was stable and generates scCO2 slowly within a few seconds. On the other hand, in the case of heating from the lower side, scCO2 was created faster within a second but natural convection and turbulence were observed. Numerical simulations of the scCO2 creation in a chamber were also performed using the COMSOL Multiphysics with a program package for themophysical properties of CO2 called the PROPATH. It showed that scCO2 creation in the heating from the upper side was stable due to the gas-like properties of the scCO2 near the heater. In the case of heating from the lower side, density distribution depended on temperature distribution firstly but after natural convection grows, flow in the chamber became disturbed and the density distribution depended not only on temperature distribution but also on the density fluctuation caused by the convection vortexes. Same tendency was observed in experimental results.