부산대학교 도서관

In most previous works, liquid hold-ups were studied by using a fixed bed soaked prior to experiments. In the present study, the characteristics of liquid hold-ups and liquid flow were investigated with initially unsoaked bed. Contact angles (θ) for these particle/liquid (tap water) systems were about 70° and 10° for fluorine-coated particles and non-coated particles. Under bad wettability condition (θ≒70°), total and static hold-ups for initially unsoaked bed packed with small balls are remarkably smaller than those for initially soaked bed. In initially unsoaked bed, total and static hold-ups under bad wettability condition (θ≒70°) indicate maximum values at about Dp =10 mm and decrease abruptly in proportion to a decrease in particle size, despite an increase in the specific surface area. Under good wettability condition (θ≒10°), total and static hold-ups are smaller than those of bad wettability condition (θ≒70°), because only restricted liquid droplets and/or liquid rivulets are formed within the packed bed for initially unsoaked bed, nevertheless liquid is easy to spread out on the solid surface under good wettability condition.