Thermally induced two-phase oscillating flow inside a capillary tube

This paper deals with thermally induced meniscus oscillations in a two-phase system consisting of a liquid plug and a vapor bubble in a capillary tube of circular cross-section. This system represents the simplest version of a heat transfer device called “pulsating heat pipe” (PHP). Our purpose is to gain fundamental understanding of the physical processes that cause self-sustained thermally driven oscillations. A visualization experiment is performed and the oscillations of the liquid–vapor meniscus and the vapor pressure are observed. We propose next a theoretical model. It differs from existing models by the account of the two-phase equilibrium that occurs locally at the vapor–liquid interface and by introduction of the time varying wetting films through which the major part of the heat and mass transfer occurs. Results from the proposed model show a good agreement with the experiment.