Numerical Simulations of Two-Phase Flow in a Dorr-Oliver Flotation Cell Model
Abstract: Two-phase (water and air) flow in the forced-air mechanically-stirred Dorr-Oliver machine has been investigated using computational fluid dynamics (CFD). A 6 m 3 model is considered. The flow is modeled by the Euler-Euler approach, and transport equations are solved using software ANSYS-CFX5. Unsteady simulations are conducted in a 180-degree sector with periodic boundary conditions. Air is injected into the rotor at the rate of 2.63 m 3 /min, and a uniform bubble diameter is specified. The effects of bubble diameter on velocity field and air volume fraction are determined by conducting simulations for three diameters of 0.5, 1.0, and 2.0 mm. Air volume fraction contours, velocity profiles, and turbulent kinetic energy profiles in different parts of the machine are presented and discussed. Results have been compared to experimental data, and good agreement is obtained for the mean velocity and turbulent kinetic energy profiles in the rotor-stator gap and in the jet region outside stator blades.
CFD MODEL OF A SELF-AERATING FLOTATION CELL
The effect of impeller speed on the air flow in a selfaerated Denver laboratory flotation cell was investigated using computational modelling. Air is induced into the slurry by the impeller’s rotating action. The rate of air flow is determined by the suction pressure created by the impeller, the hydrostatic head of the slurry and the frictional losses along the delivery shaft from the inlet valve to the impeller. From two-phase simulations of the flotation cell at varying impeller speeds, the predicted air flow rates have been found to compare favourably against measured values reported in the literature. The effect of increasing impeller speed is to increase the air flow rate and gas holdup in the cell. Simulations with flotation kinetics showed that the gravitational force acting on the attached particles is significant. The effect is a decrease in the bubble rise velocity which in turn affects the flotation rate as predicted by the model.
Working Knowledge: Employee Innovation and the Rise of Corporate Intellectual Property, 1800-1930
This book presents the legal and business history of corporate ownership of employee knowledge. Skilled workers of the early nineteenth century enjoyed a degree of professional independence because workplace knowledge and technical skill were their 'property,' or at least their attribute. In most sectors of today's economy, however, it is a foundational and widely accepted truth that businesses retain legal ownership of employee-generated intellectual property. In "Working Knowledge", Catherine Fisk chronicles the legal and social transformations that led to the transfer of ownership of employee innovation from labor to management. This deeply contested development was won at the expense of workers' entrepreneurial independence and ultimately, Fisk argues, economic democracy. By reviewing judicial decisions and legal scholarship on all aspects of employee-generated intellectual property and combing the archives of major nineteenth-century intellectual property - producing companies - including DuPont, Rand McNally, and the American Tobacco Company - Fisk makes a highly technical area of law accessible to general readers while also addressing scholarly deficiencies in the histories of labor, intellectual property, and the business of technology.