Hydrodynamics of counter-current two phase flow through porous media

Understanding of the hydrodynamic characteristics and flow limitations of two-phase flow through porous media is necessary to evaluate the coolability of a top flooded nuclear reactor core. In the present work, and analytical and experimental investigation of countercurrent two-phase flow through 80 to 100 cm deep porus layers composed of both uniform size spherical particles (nominal diameters 1 to 19 mm), mixture of these particles, and mixtures of spherical paricles and nonspherical sharps has been performed. The porous layers were formed in a 20-cm dia plexiglass tube. Water and air were used as the test fluids, with superficial velocities ranging from 0 to 19.5 mm/s and 0 to 163 mm/s, respectively. Bed porosity, mean particle diameter, flooding limits, and void fraction and pressure gradient at flooding were investigated. An analytical approach based upon geometrical models was used to derive expressions for porosity and mean particle diameter. An empirical correlation has been found for the flooding data which is slightly different than that found in the literature. The effect of coupling of the overlying liquid layer with the bed and of axial gas injection upon the flooding limit were also studied. Results of these hydrodynamic investigations were applied to obtain dryout heat flux in bottom and volume heated particulate beds