Application of laser holography interferometer to heat transport phenomena near the critical point of nitrogen

摘要

A laser holography interferometer is applied to investigate heat transport phenomena near the critical point of nitrogen. The very high thermal compressibility and small thermal diffusion near the critical point of fluids affect thermal energy propagation, lead to the formation of weak acoustic waves as carriers of thermal energy. This heat transfer phenomenon is called the piston effect. The piston effect in supercritical nitrogen is investigated using a laser holography interferometer. Natural convection due to gravity interferes with the piston effect under terrestrial conditions. Therefore, we attempt to suppress the generation of natural convection by creating stable density stratification in the cell. The experiment consisted of two different procedures. In the first, heat was added from the bottom of the experimental cell, while in the second, heat is added from the top of the cell. From the two results, we successfully extracted the heat transfer phenomenon, the piston effect, which is considered to be the fourth mechanism of heat transfer.