Effect of Pressure Drop Owing to Friction between Pipe Inner Wall and Water on Non-equilibrium Flow Fields in an Air-lifting Pipe /Fundamental study on lifting system for mining marine mineral resources

摘要

The present paper is concerned with a theoretical analysis of the steady characteristics of an air-lift pump system for conveying the marine mineral resources from the deep-sea bed to the sea surface. Here, the effect of pressure drop owing to the friction between the fluid and the inner wall of the pipe is taken into consideration. Some numerical experiments have been carried out using a set of five equations in the solid-liquid two-phase region and a set of eight equations in the solid-gas-liquid three-phase region for determining the non-equilibrium flow properties. In particular, the influence of the pipe diameter as well as the liquid-phase velocity on the solid-phase mass flux to be lifted has been examined from a numerical point of view. It has been quantitatively demonstrated how the mass flux of mineral ores decreases because the pressure drop due to the wall friction becomes more remarkable as the liquid-phase velocity is higher and the pipe diameter is selected to be smaller. Again, the critical condition whether or not solid particles can be lifted has been indicated with the liquid-phase velocity and the pipe diameter as parameters. Such important problems are described in detail.