A laboratory of two phase flowing system with the height of overall 4.3m and net 3.6m was established to understand and analyze the flow characteristics of small particles including pressure drop and hydraulic gradient in the hydraulic pumping system. The experimental results show that the pressure drop and hydraulic gradient in the tube increase because the in-situ volume fraction of solid particles in the tube increases when the discharge volume fraction of solid particles increases. And the pressure drop in the tube also increases because the terminal settling velocity of the solid particles increases when the size of the particles becomes larger. On the other hand, the pressure drop and hydraulic gradient in the tube decrease as the tube diameter increases because of reduction of friction loss.
The flow system such as the hydraulic pumping or the air lifting system is reported to be suitable for the commercial lifting among the lifting techniques, by which the manganese nodules that are deposited on the seafloor 5,000 m below the sea-level are lifted through the lifting pipe to the mining vessel with seawater. The hydraulic pumping system is the two-phase lifting technology of solid and liquid. Up to now, studies on the hydraulic transportation systems of liquid-solid two phase mixture have been performed by many researchers. Newitt et al. (1961) performed an experiment to predict the hydraulic gradients and flow rates of water and solid particles in the pipe of I inch in diameter. Sumardi & Chung (1996) have performed an experiment with a closed flow-loop testing system that conveyed silica sands to predict the pressure drops as well as the hydraulic gradients of water-solid mixtures. Their dada are especially valuable because they made direct instrument measurements using the mass flowmeter, electromagnetic flowmeter and DP gauge.