Pawel Kosinski

Eulerian-Eulerian CFD Model for the Sedimentation of Spherical Particles in Suspension with High Particle Concentrations

Abstract A computational study of the process of sedimentation of spherical particles in suspensions with high particle concentrations has been performed with the two-fluid Eulerian approach. The solid stress induction in the dispersed phase was modelled through modification of the suspension viscosity. Convectional flow patterns were found and studied during the simulations. The presence of these patterns, which are also observed experimentally, makes the sedimentation process dependent on the rheological behaviour of the suspension. The results of the simulation were validated with experimental results. The present paper shows that Eulerian-Eulerian simulations can account for some of the detailed processes taking place in a settling suspension of particles.

Explosion suppression by a cloud of particles

In this paper, we pay attention to the problem of particle evacuation from a high-pressure region. This research was inspired by the known problem of the explosion suppression by a cloud of inert and solid particles. This issue has been so far investigated experimentally where the most important tasks have been to find the proper suppressant, estimate its quantity, as well as design the quenching device. Also some attention has been paid to numerical investigation where by use of computer simulation the same questions have been asked. In this paper, we focus on the numerical study, where the first moment of the suppressing process is analysed: the exact behaviour of the particle cloud as it interacts with the gas. A mathematical model is presented that bases on the Eulerian-Lagrangian approach for the description of the gas and solid phases. Finally, some results are shown: both snapshots of particle location as well as some statistics, such as particle cloud area and particle distribution within the cloud. According to the observations, we obtain different behaviour especially if the particle diameter varies. For some values the particles do not seem to be well-distributed and an example are smaller particles that tend to gather along the edges of the eddies formed in the gas phase.

Characterization of carbon black modified by maleic acid

We present here a method for modifying the surface of carbon black (CB) using a simple heat treatment in the presence of a carboxylic acid as well as water or ethylene glycol as a solvent. CB was mixed with maleic acid and either water or ethylene glycol, and heated at 250°C. Unlike the traditional surface modification processes which use heat treatment of carbon with mineral acids the present modification method using a carboxylic acid proved to be simple and time efficient. CB from two different vendors was used, and the modified samples were characterized by TGA, BET surface area measurement, XRD, particle size and zeta potential measurements, and FTIR. It was found that several material properties, including thermal stability and surface area, of the modified CB are significantly altered relative to the parental carbon samples. This method provides a rapid and simple route to tailor new materials with desired properties.

Mechanisms of Non-Newtonian Polymer Flow Through Porous Media Using Navier–Stokes Approach

This study includes solving non-Newtonian Navier–Stokes equation in three-dimensions (real rock images) and two-dimensions (simplified pore geometries) using the finite-difference method. The purpose of this study is to improve understanding of local phenomena leading to the mobilization of residual oil. This involves local pressure variations for non-Newtonian polymers and compares it with Newtonian fluid behavior. When a higher degree of shear thickening is induced, more flow diversion to side channels perpendicular to the main flow path and larger drag on fluids inside side channels will occur. This is consistent with oil mobilization and lowering of residual oil saturation.

Effect of Temperature on the Transformation of Carbon Black into Nanotubes

In this paper, successful structural transformation of carbon black (CB) into nanotubes and nanoonion like structures at relatively low temperatures in the presence of transition metal catalyst is reported. This study focuses also on the influence of the temperature on the structural transformation of CB into nanostructures. The experiments were carried out at 700°C and 1000°C in a horizontal tube furnace under N2 atmosphere. The obtained samples were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM). It was found that increase in the synthesis temperature from 700°C to 1000°C influences the morphology of the produced nanotubes significantly and the degree of crystallinity also increased with the temperature..

Combined CFD/Population Balance Model for Gas Hydrate Particle Size Prediction in Turbulent Pipeline Flow

A combined computational fluid dynamics/population balance model (CFD‐PBM) is developed for gas hydrate particle size prediction in turbulent pipeline flow. The model is based on a one‐moment population balance technique, which is coupled with flow field parameters computed using commercial CFD software. The model is calibrated with a five‐moment, off‐line population balance model and validated with experimental data produced in a low‐pressure multiphase flow loop.

Numerical study on the dynamics of a jet-vortex interaction

The interaction of a vortex and a jet plays an important role for many industrial processes such as carbon black formation or combustion in diesel engines. The knowledge of physics of these phenomena is crucial for engineers, but also for scientists who wish to study this complex flow pattern. In this research, we numerically investigate cases where a cylindrical reactor is charged with gas injected through five ports. The first one is located along the main axis of the cylinder and this leads to the formation of the main jet. The other four ports are situated along the side walls such that the gas entering the cylinder tangentially through them causes a vortex to be formed. The objective of this paper is to show the fundamental physical phenomena and also how the initial and boundary conditions influence the results. It is shown how the process is influenced not only by modifying the velocity of injected gas, but also by the orientation and position of the vortex inlet nozzles.

Eulerian‐Eulerian Simulation of Sedimentation of Uniformly‐sized, non‐Brownian Spheres in Viscous Fluids

A Eulerian‐Eulerian 3‐dimensional CFD‐model has been built in order to study the sedimentation process of uniformly‐sized, non‐Brownian spheres in a viscous fluid. It is shown that proper agreement with experimental data for high particle loadings strongly depends on using a correct drag force relation. Convection currents in the carrier phase were observed during simulation. They were found to present a hydraulic resistance to the solids settling. The particle interactions were implemented through a solids stress tensor dependent on the viscosity of the carrier phase and the solids local volume fraction. The completed model was validated by comparison with experimental data.

Non-invasive studies of multiphase flow in process equipment. Positron emission particle tracking technique.

Positron emission particle tracking (PEPT) is a novel experimental technique for non-invasive inspection of industrial fluid/particle flows. The method is based on the dynamic positioning of a positron-emitting, flowing object (particle) performed through the sensing of annihilation events and subsequent numerical treatment to determine the particle position. The present paper shows an integrated overview of PEPT studies which were carried out using a new PET scanner in the Bergen University Hospital to study multiphase flows in different geometric configurations.

Numerical study of gas-liquid flow morphology in a vertical flowmeter nozzle

Industrial multiphase flow measurement systems often contain meters based on Venturi principle. Those instruments deal with the differential pressure measurements whose accurate interpretation is possible when the flow morphology is known a-priori. The present paper reports the results of CFD-modelling of a gas-liquid flow through a vertical nozzle accompanied by a blind-T flow conditioner. The model is used for evaluation of the flow morphology in case the volume fractions of both phases are comparable. The model demonstrates high non-uniformities of the flow field after the blind-T, which indicates that this type of flow conditioners may lead to inaccurate results.Industrial multiphase flow measurement systems often contain meters based on Venturi principle. Those instruments deal with the differential pressure measurements whose accurate interpretation is possible when the flow morphology is known a-priori. The present paper reports the results of CFD-modelling of a gas-liquid flow through a vertical nozzle accompanied by a blind-T flow conditioner. The model is used for evaluation of the flow morphology in case the volume fractions of both phases are comparable. The model demonstrates high non-uniformities of the flow field after the blind-T, which indicates that this type of flow conditioners may lead to inaccurate results.