Transition from boiling to free convection in supercritical fluid

Observations of abnormal convection similar to boiling in supercritical fluids have been reported for many years. Recently, a molecular dynamics study performed by the authors clarified that even at the supercritical pressure, an interface accompanied with interfacial tension exists in fluids under a temperature gradient. Such findings have led us to think that the abnormal convection observed slightly above the critical point, which has been called the boiling-like phenomenon, is nothing but a boiling phenomenon. Here we report from this point of view, an experimental observation of the transition from boiling at subcritical pressure to ordinary free convection far above the critical pressure. Visual observation and measurement of the critical heat flux shows that with pressure elevation the phenomenon changes gradually and continuously from boiling to free convection with no drastic changes. The point at which boiling characteristics disappear lies slightly above the critical pressure.