Afshin Goharzadeh

Examining Asphaltene Solubility on Deposition in Model Porous Media

Asphaltenes are known to cause severe flow assurance problems in the near-wellbore region of oil reservoirs. Understanding the mechanism of asphaltene deposition in porous media is of great significance for the development of accurate numerical simulators and effective chemical remediation treatments. Here, we present a study of the dynamics of asphaltene deposition in porous media using microfluidic devices. A model oil containing 5 wt % dissolved asphaltenes was mixed with n-heptane, a known asphaltene precipitant, and flowed through a representative porous media microfluidic chip. Asphaltene deposition was recorded and analyzed as a function of solubility, which was directly correlated to particle size and Péclet number. In particular, pore-scale visualization and velocity profiles, as well as three stages of deposition, were identified and examined to determine the important convection-diffusion effects on deposition.

Measurement of fluid velocity development in laminar pipe flow using laser Doppler velocimetry

In this paper we present a non-intrusive experimental approach for obtaining velocity gradient profiles in a transparent smooth pipe under laminar flow conditions (Re = 925) using a laser Doppler velocimeter (LDV). Measurements were taken within the entrance region of the pipe at l = 300 mm and l = 600 mm from the pipe inlet, in addition to measurements of the fully developed flow at l = 1800 mm. The obtained results show how the velocity profile from upstream of the pipe develops into a classical laminar profile downstream, which matches the theoretical profile well. Additionally, a brief summary of historical information about the development of flow measurement techniques, in particular LDV, is provided.

Experimental Measurement of Laminar Axisymmetric Flow Through Confined Annular Geometries With Sudden Inward Expansion

In this paper, separating and reattaching aqueous laminar flows produced by a sudden inward expansion within confined annular geometries are experimentally studied. The test geometries are based on a previous numerical study. The fluid flow structure at the expansion region is experimentally characterized using particle image velocimetry combined with refractive index matching. The detailed measurements of the velocity field, reattachment length, and relative eddy intensity are obtained for two different expansion ratios, 1.4 and 1.6. For both expansion ratios, the reattachment length is found to vary nonlinearly with the Reynolds number (50 <Re <600), in line with numerical predictions. The eddy intensity is found to depend strongly on both the Reynolds number and expansion ratio with the relationship between the Reynolds number and the reattachment length being nonlinear. Overall, the corresponding numerical predictions are in good agreement with the measurements undertaken herein.

Experimental Characterization of Slug Flow on Solid Particle Transport in a 1 Deg Upward Inclined Pipeline

This paper presents an experimental investigation on the influence of hydraulic and two phase (gas-liquid) flows on sand dune transportation resulting from a stationary flatbed, for horizontal and 1 deg upward pipe inclination. For gas-liquid conveying of solid particles, pipe inclination resulted in considerably different transport phenomena relative to those observed for horizontal orientation. Key distinguishing features such as backward bed movement and enhanced particle suspension were observed and were found to be highly gas-liquid ratio dependent. Using image processing, the solid particle suspension layer was quantified as a function of the gas-liquid flow. The measurements presented provide fundamental insights into the influence of upward pipe inclination on bed-load mode solid transportation in a closed conduit.

Influence of Gas-Liquid Two-Phase Intermittent Flow on Hydraulic Sand Dune Migration in Horizontal Pipelines

This paper presents an experimental study of three-phase flows (air-water-sand) inside a horizontal pipe. The results obtained aim to enhance the fundamental understanding of sand transportation due to saltation in the presence of a gas-liquid two-phase intermittent flow. Sand dune pitch, length, height, and front velocity were measured using highspeed video photography. Four flow compositions with differing gas ratios, including hydraulic conveying, were assessed for sand transportation, having the same mixture velocity. For the test conditions under analysis, it was found that the gas ratio did not affect the average dune front velocity. However, for intermittent flows, the sand bed was transported further downstream relative to hydraulic conveying. It was also observed that the slug body significantly influences sand particle mobility. The physical mechanism of sand transportation was found to be discontinuous with intermittent flows. The sand dune local velocity (within the slug body) was measured to be three times higher than the averaged dune velocities, due to turbulent enhancement within the slug body.

An experimental and numerical investigation of tube bank heat exchanger thermofluids

Heat exchangers are extensively used in engineering applications, such as for the thermal management of electronic cabinets. Although computational fluid dynamics (CFD) has the potential to provide a more accurate assessment of exchanger thermal performance than empirically-based software, CFD-based parametric analysis of a wide range of exchanger geometries and Reynolds numbers can be computationally prohibitive. This paper proposes and assesses the effectiveness of a dual design strategy, which combines empirical and numerical analyses of heat exchanger thermofluid performance. Empirical analysis serves to provide initial design specifications, while performance is optimized using CFD. The test vehicle consists of a staggered tube bank heat exchanger arrangement (St = Sl = 3.0). Good agreement is obtained between the empirical relationships developed by Martin [ 1 ] for heat transfer and Gaddis and Gnielinski [2] for pressure drop, and corresponding CFD predictions for Reynolds numbers varying from 1,749 to 17,491. Numerical flow field predictions are found to be accurately predicted relative to particle image velocimetry (PIV) measurements for a Reynolds number of 700. This study therefore provides a degree of confidence in using empirical correlations to undertake an initial sizing of tube bank heat exchanger design, to be refined for application specific environments using CFD analysis.

Influence of Pipeline Inclination on Hydraulic Conveying of Sand Particles

The understanding of sand particle transport by fluids in pipelines is of importance for the drilling of horizontal and inclined hydrocarbon production wells, topside process facilities, infield pipelines, and trunk lines. Previous studies on hydraulic conveying of sand particles in pipelines have made significant contributions to the understanding of multiphase flow patterns, pressure drop and particle transport rate in horizontal pipelines. However, due to the complexity of the flow structure resulting from liquid-sand interactions, the mechanisms responsible for bed-load transport flow for hydraulic conveying of sand particles have not been extensively studied in inclined pipelines. This paper presents an experimental investigation of hydraulic conveying of sand particles resulting from a stationary flat bed in both horizontal and +3.6 degree upward inclined pipelines. The characteristics of sand transportation by saltation from an initial sand bed are experimentally visualized using a transparent Plexiglas pipeline and high-speed digital photography. The dune formation process is assessed as a function of pipeline orientation. Based on the visualized dune morphology, pipeline inclination is found to have a significant influence on hydraulic conveying of sand dune dynamics (i.e., dune velocity), as well as sand dune geometry (i.e., dune pitch and characteristic dune angles).Copyright

Parametric Performance Analysis of an Electrostatic Wire-Cylinder Aerosol Separator in Laminar Flow Using a Numerical Modeling Approach

A numerical methodology based on the Lagrangian approach is outlined to study the performance of a select class of electrostatic aerosol separators. This modeling method is used to perform a parametric study on the efficiency of a wire-cylinder separator in separation of water aerosols from air. The geometry consists of an 80 µm diameter wire placed in the centerline of a 20 mm diameter cylinder. The work focuses on the effect of applied voltage (in the range of 4 to 8 kV), flow velocity (in the range of 0.3 to 1.5 m/s), flow temperature (in the range of 280 K to 320 K), and separator length (in the range of 0.05 to 0.15 m) on charging of water aerosols and on separator collection efficiency in laminar flow. The aerosols size ranges between 0.01–10 µm. The results of the study show that applied voltage, flow rate, and separator length affect the separation efficiency significantly, while the effect of flow temperature seems negligible.

Experimental Characterization of Slug Flow Velocity Distribution in Two Phase Pipe Flow

This paper presents an experimental study of gas-liquid slug flow inside a horizontal pipe. The influence of air bubble passage on liquid flow is characterized using Particle Image Velocimetry (PIV) combined with Refractive Index Matching (RIM) and fluorescent tracers. A physical insight into the velocity distribution within slug flow is presented. It was observed that the slug flow significantly influences the velocity profile in the liquid film. Measured velocity distributions also revealed a significant drop in the velocity magnitude immediately upstream of the slug nose. These findings aim to aid an understanding of the mechanism of solid transportation in slug flows.Copyright

INFLUENCE OF SLUG FLOW ON HYDRAULIC SAND DUNE MIGRATION IN HORIZONTAL PIPELINES

This paper presents an experimental study of three phase flows (air-water-sand) inside a horizontal pipe. The results obtained aim to enhance the fundamental understanding of sand transportation due to saltation in the presence of slug flow. Sand dune pitch, height and front velocity were measured using high-speed video photography. Four flow compositions with differing gas ratios, including hydraulic conveying, were assessed for sand transportation, having the same mixture velocity. For the test conditions under analysis, it was found that the gas ratio did not affect the average dune front velocity. However, for slug flows, the sand bed was transported further downstream relative to hydraulic conveying. It was also observed that the slug body significantly influences sand particle mobility. The physical mechanism of sand transportation was found to be discontinuous with slug flows. The sand dune local velocity (inside the slug body) was measured to be three times higher than the averaged dune velocities.Copyright