亜臨界領域における二酸化炭素の凝縮液の挙動(<小特集>異相界面における諸現象の物理)

抄録

Authors have being studied natural convection heat transfer of carbon dioxide in the subcritical region and observed condensate flowing along the vertical cylinder. Near the critical point, physical properties of fluids show remarkably different behavior from those for lower pressure region. A very low difference of density between vapor and liquid causes that the buoyancy becomes comparable to the gravity force, so that the flow velocity of condensate decreases. A small value of latent heat makes the amount of condensate very large. These result in a thick layer of the condensate film. On the contrary, as the temperature approaches the critical temperature, the surface tension decreases sharply and becomes zero. This very low value makes the condensate film breakable. As hydrodynamics of the condensate affects condensation heat transfer, based on observing condensate flow and measuring condensate volume, the flow of condensate was classified into four regimes : the smooth laminar flow, wavy flow, wavy flow with sharp crest and wavy flow with scattered droplets.