POROUS-MEDIUM MODEL FOR 2-PHASE FLOW IN MINI CHANNELS WITH APPLICATIONS TO MICRO-HEAT PIPES

In this paper the porous medium concept is adopted to build up a funda mental model for two-phase flows inside mini channels. The capillary f orce which appears important for those problems is rigorously included in the model by following the same treatment as for porous media. Var ious applications of the developed model are demonstrated, among which are adiabatic co- and counter-current flows and heated forced and nat ural convective flows. Some fundamental results such as the two-phase pressure drop in a downflow, the flooding limit in a counter-current f low and dryout heat flux in natural convection boiling, are achieved a nd compared with previous studies available in the literature. With th e main emphasis on the application to micro heat pipes, the model is u sed to predict the capillary limit of an operating micro heat pipe, to explain the liquid holdup phenomenon and to imply the onset and origi n of the plug flow pattern. Future research needs are pointed out to - refine this first version of a two-phase model and to apply it to addi tional practical applications.