Interfacial Film Dynamics of Oscillating Plug/Slug Flows in Mini/Micro Channels

The liquid film thickness of a plug bubble in a micropipe is of interest in micro heat pipe, microfluidics, and two-phase flows. A novel optical technique was further extended to measure the liquid film thickness of a plug like bubble in a capillary pipe utilizing spatial fringe scattering method. The scattered fringes were measured by CCD camera and the calculated spatial frequencies were used to determine the film thickness between the plug and the wall. To demonstrate the capability of the newly developed technique, a validation experiment was conducted with water/air and water-honey-mixture/gas-plug flows. The velocity dependent film thickness can also be observed using this measurement technique. The interfacial film dynamics of oscillating plug/slug flows in a capillary channel was investigated. The Ripple effect of film thickness was observed when the oscillating frequency reached 2Hz. This newly developed method is easy to be implemented and it will be a very useful technique for micro heat pipe research.