In a spiral tube twisted with a constant pitch in relation to the axis, a swirling flow occurs when fluids flow in the tube. Solid particles in multiphase flows are mixed by the swirling flow. It has been established from the experimental results that the values of the critical velocity and the pressure loss decrease in comparison with these values in a circular pipe. Thus, the hold up phenomena of the multiphase flow does not occur in the spiral tube under a low velocity range. This review presents, the experimental data of the pressure drop and the velocity distribution of the single phase flow in the spiral tube, and the experimental results of the hydraulic and the pneumatic conveyance test of solid particles, respectively. It is pointed out that in practical application, the spiral tube presents a very useful method for preventing the holdup phenomenon in a transport pipeline for the hydraulic or pneumatic conveyance of highly concentrated solid particles.
The external loop airlift bubble column facilitates the contact between gas, liquid and solid phases, since a relatively high recirculating liquid velocity is brought about by only sparging gas into liquid without any mechanical agitation. It is due to the higher recirculating liquid velocity that various properties such as gas holdup, mass transfer, etc. in the column differ from those in the conventional bubble column. The present status of knowledge of airlift column behavior is described with a brief survey on applications such as biological and chemical reactors. The areas in which further reserch is needed are also discussed.
In this work, numerical analysis have been performed to the equilibrium shape and stability of a liquid bridge adhered between two arbitrarily inclined spheres without gas flow. This problem was formulated to investigate the minimum potential energy of a drop and solved by using the finite element method. Equilibrium shape and stability depend on the nondimensional Bond number, which represents the ratio of surface tension to gravity, the given liquid volume, the inclined angle and the distance between the two spheres. Results of stability judged from the minimum eigenvalue indicate the minimum and maximum value of liquid volumes and the of of parameters on the values, with the exception of two attached spheres, where the critical volumes only have maximum values. However, in the case of two vertical spheres, it was necessary to decide the maximum volumes because of the experimental observation. The maximum volumes were set as the volumes at the time when the lower contact line of a drop reaches the halfway line of the lowersphere.
An experimental investigation was conducted concerning the circumferential variations of the characteristics of a liquid film formed on the inner surface of a round tube. Attention was paid to the characteristics of the disturbance wave which plays important roles in the maintenance a liquid film near the top of the tube and the transportation of liquid. The circumferential variations of film thickness parameters and the effect of pipe inclination on those parameters were examined. The main results are summarized as follows:(1) Wave height of the base film, hB, is approximately equal to the mean base film thickness, tBm, and the effect of pipe inclination and flow rates of both air and water on hB is qualitatively the same as that on tBm, (2) Disturbance wave height is five to twenty times of tBm, and it depends strongly on superficial water velocity, j1, while tBm has a weak dependence on j1.(3) The generation of a disturbance wave is mainly controlled by the flow condition of the base film at the bottom.(4) The flow mechanism of the base film changes at the liquid flow rate of j1=0.04m/s.