Investigation of boiling and bubble confinement in a high aspect ratio micro-channel

In this paper we experimentally investigated the pressure drop fluctuation and liquid/vapour interface behaviours during flow boiling in a single rectangular micro-channel with high aspect ratio. An integrated testing system including syringe pump, pressure sensors, thermocouples, micro-channel and high speed camera was mounted in a 1 m × 1 m × 1 m plexiglass box, the ambient temperature inside of which was controllable. A micro-channel with the hydraulic diameter of 727 μm was chosen, the aspect ratio of which was 10. FC-72 was used as the working liquid, with a saturation temperature of 56 °C at atmospheric pressure. The present study concentrated on the transition from single-phase flow to two-phase flow (including single-phase friction losses and onset of nucleation) and flow instabilities and liquid–vapour interface behaviors during two-phase flow. Pressures at inlet (Pin) and outlet (Pout) of the channel were measured and pressure drop (Pin − Pout) was then obtained. The pressure drop fluctuation was discussed. Besides, various liquid–vapour interface behaviors including interface deformation, recoiling and re-wetting as well as bubble nucleation, bubble growth and bubble geometry were captured and analyzed with the aid of a high speed camera. Additionally, evaporation rates of bubble nose and bubble tail at different mass fluxes and heat fluxes were compared