The paper presents an approach to compute and scale-up the wear rate distribution in the cross-section of slurry pipelines. The wear rate is related to the energy dissipated by particle-wall interaction. The velocity and concentration distributions are determined with a multiphase turbulent flow model. The approach was tested for horizontal and inclined pipelines transporting solids with narrow and broad size distributions. A parametric study for a phosphate slurry pipeline is presented.
Solid-liquid mass transfer coefficients have been obtained by measuring the ion-exchange rate in a gas-liquid-solid three-phase upflow through a vertical tube. The three phase is composed of nitrogen gas, an electrolyte solution, and cation-exchange resin beads of 941μm in diameter. Other experimental variables are slurry velocity, gas velocity, and temperature. The mass transfer coefficients increased according to increases in the slurry velocity, gas velocity, and temperature. The experimental results have been correlated by the following equation, previously proposed for a solid-liquid two-phase tube flow: Sh=2+0.47(ε1/3Dp4/3/υ)0.63Sc1/360<(ε1/3Dp4/3/υ)<400, 269<Sc<641, md<0.01 where ε, Dp, ν, and md are energy dissipation rate per unit mass of liquid, particle diameter, kinematic viscosity, and delivered concentration of particles, respectively.
Experiments were conducted to investigate pressure drop, liquid holdup and the stable operating range of a low height packed column with regularly packed metal Raschig rings having very a large fractional void space. These factors are important parameters when designing gas-liquid countercurrent flow low height packed columns. Regularly packed beds considerably reduce the pressure drop compared to that of random packed beds and/or plate columns. The total pressure drop appears to be smaller than the total liquid holdup. Therefore, Major factors causing pressure drop are the contraction and expansion of gas and the friction loss between gas and liquid. A macroscopic model based on the estimation of the total pressure drop was formulated and compared with experimental data of the present study. The model provides a functional way of correlating the pressure drop by using information obtained in this study of the liquid holdup and the correction factor. Furthermore, the stable operating ranges were established by parameters previously investigated by the authors.
Experiments and numerical calculations were carried out on the dynamic behavior of the solitary wave of a flowing liquid. Data on the wave propagation velocity, the wave profile, and the liquid velocity profile were presented. Results of the numerical calculations agreed with the experimental results in respect of the above-mentioned qualities which characterize the solitary wave. Thus, the applicability of this numerical calculation method was verified. Based on the experimental results and the numerical calculations, simple correlation equations, which express the relationships between the solitary waves of the stationary liquid and of the stratified liquid flow were deduced. The applicability of Benjamin's theory on the solitary wave of a flowing liquid was also verified.
In order to remove snow from an area where application of conventional techniques encounters difficulties, hydraulic conveying of the snow using a pump and pipe-line is beginning to be considered an alternative. However, instruments and engineering principles for such a technique are still to be developed. With this aim, the improvement of a water separator, a device to control snow fraction, was attained and consequently, investigations were conducted on its applicability as a gate valve for a snow/water mixture and on the mechanism of snow choking the channel. The water separator designed in this research was successfully applied to raise the snow fraction up to 40%, or to concentrate the mixture to make the snow fraction higher by a factor of 3. The mixing of granulated-snow did not increase the pressure drop at the gate valve and choking was avoided, providing that the ice blocks contained in the mixture, were not larger than the opening at the gate. The choking of the channel due to snow was classified into two categories and consequently, the relevant mechanisms for each of them were also clarified. These results provide useful engineering information on avoiding choking of the channel with snow, which is one of the greatest obstacles in the practical application of hydraulic covering of snow.