Application of Visualization Techniques to Heat Transport Phenomena in Supercritical Nitrogen

This paper describes the results of a visualization study of the phase transition process and heat transport phenomenon in supercritical nitrogen. An experimental apparatus for the visualization study is designed to observe the heat transport phenomena. The experimental cell is a rectangular parallelepiped surrounded with two optical windows, a ceiling, two side-walls made of Bakelite and a planar heater at the bottom. Heat is applied in step functions from the planar heater. The phase transition from the vapor/liquid equilibrium state to the supercritical state is observed by the use of a shadowgraph technique. On the other hand, the heat transfer phenomenon in supercritical nitrogen is investigated using a laser holographic interferometer. The initial temperature gradient, which suppresses the generation of convection, is made in the experiment. We can successfully observe the heat transport phenomenon that the convection and piston effect carry thermal energy in supercritical nitrogen.