The individual phase holdups in two (liquid‐air, liquid‐solids) and three (liquid‐air‐solids) phase fluidized beds have been measured over a wide range of liquid and gas velocities. Ex‐periments were canied out in a large two‐dimensional bed. Three solids were used ranging in size from 1 to 6 mm. The effect of viscosity (1‐70 cp) was determined using solutions of sugar and carboxymethyl cellulose of different concentrations. Various acetone‐water mixtures were employed to examine the effect of surface tension in the range 40‐73 dyne/cm. Beds of particles having a minimum fluidizing velocity in the liquid of less than 1.28 cm/sec were found to initially contract upon the injection of gas. In contrast, beds of particles having minimum fluidizing velocities exceeding tins value were found to expand.

The hydrodynamics of two (water-air, water-solids) and three (water-air-solids) phase fluidized beds have been studied in a large two-dimensional column. Two solids were used, namely 6 mm glass beads and 2.6 mm irregular gravel.