Experimental
The solid foams used in this study are commercially available under the brand name of Duocel from ERG Aerospace Corp. (flat rectangular blocks of size 30 × 30 × 1 cm). Fig. 1 shows the details of the solid aluminium foam for 10 and 40 ppi.
All of these foams have a voidage of 92–94%. The foams were placed in a specially designed semi two-dimensional column with varying height; either 30, 60, or 90 cm high with cross section 30×1 cm, shown schematically in Fig. 2. Air–water is used as the gas–liquid two-phase system in this study. The air and water are flowing co-currently. The liquid enters the bottom of the column through five distribution holes placed along the complete width of the column and the flow rate is measured and controlled by a coriolis mass flow meter (Rheonik) and Badger control valve. The gas enters through five distributor blocks each with 20 holes of 0.5mm in diameter and independently controlled by a Brooks thermal mass flow controller. The maximum gas and liquid flows within the column are 1.4 and 0.1ms−1, respectively. The liquid is recycled via a gas–liquid separator back to the supply vessel feeding the pump. In the gas–liquid separator the liquid level is measured to determine the liquid holdup in the column with the solid foam. The liquid temperature is maintained at approximately 30 ◦C. To ensure complete wetting of the packing, the column is completely filled with liquid and thereafter the experiments are conducted at various gas and liquid velocities.