NDLI: Effect of a Symmetric Contraction on the Concentration Profiles of a Particle-Laden Slurry

Content Provider	The American Society of Mechanical Engineers (ASME) Digital Collection
Author	Deshpande, A. Ramisetty, K. Chambers, F. W. Mcnally, M. E. Hoffman, R. M.
Copyright Year	2011
Abstract	In-line measurements and sample stream withdrawals for on-line and/or at-line measurements of slurries flowing in horizontal pipes can be complicated by nonuniform slurry profiles. More uniform profiles would improve measurements. Area contractions are a common means used to produce more uniform velocity fields for single phase flows. For example, contractions are used to condition the flow entering wind tunnel test sections and make velocity profiles more uniform at venturi throats. It was desired to determine whether area contractions could be used to make slurry concentration profiles more uniform in horizontal pipe flows. An ASME flow nozzle with a contraction diameter ratio of 0.5 was chosen as a well defined geometry to consider in a Computational Fluid Dynamic (CFD) study of the effects of a contraction on slurry concentration profiles. The pipe was 2.8 m long with a 50.8 mm diameter. The entrance of the contraction was placed at 35 pipe diameters from the inlet in fully developed flow. A length of 20 diameters followed the contraction. The slurry had a xylene liquid phase and an ADP solid phase with a density ratio of 1.7. The simulations were performed at primary phase velocities of 2 m/s and 4 m/s, corresponding to Reynolds numbers of 1.4E05 and 2.8E05. Spherical particle diameters of 38, 75, and 150 μm were used at concentrations of 0.05, 0.2, and 0.3. ANSYS FLUENT 12 software was used with the standard k-ε turbulence model and standard wall function. The mixture multi-phase model was used for the two-phase flow. An unstructured tetrahedral meshing scheme was used with 1.4 million elements. The grid was adjusted until the condition 30 < y+ <60 for the mesh point nearest the wall was satisfied. A grid refinement study was performed to insure grid independence. The computational scheme first was validated by comparing pipe flow velocity and concentration profiles to results in the literature. The computations performed with the contraction showed that in all cases the concentration profiles of the solid particles displayed greater uniformity than the profiles in the pipe upstream of the contraction. The effect of the contraction was more pronounced for the larger particles. As in the case of single phase flows, the contraction caused the axial turbulence intensity to decrease. The greater uniformity of the concentration profiles at the exit plane of the nozzle, suggest that the contraction can provide better conditions for performing measurements of a particle-laden slurry.
Starting Page	333
Ending Page	342
Page Count	10
File Format	PDF
ISBN	9780791854921
DOI	10.1115/IMECE2011-62809
Volume Number	Volume 6: Fluids and Thermal Systems; Advances for Process Industries, Parts A and B
Conference Proceedings	ASME 2011 International Mechanical Engineering Congress and Exposition
Language	English
Publisher Date	2011-11-11
Publisher Place	Denver, Colorado, USA
Access Restriction	Subscribed
Subject Keyword	Turbulence Computational fluid dynamics Pipe flow Wind tunnels Computer software Reynolds number Flow (dynamics) Density Geometry Venturi tubes Simulation Computation Two-phase flow Particulate matter Nozzles Engineering simulation Pipes Slurries
Content Type	Text
Resource Type	Article

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