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Research Papers: Multiphase Flows

Experimental Study and Computational Fluid Dynamics Modeling of Pulp Suspensions Flow in a Pipe

[+] Author and Article Information
Carla Cotas

Chemical Engineering and Forest Products
Research Centre (CIEPQPF),
University of Coimbra,
Coimbra 3030-790, Portugal
e-mail: carlacotas@gmail.com

Bruno Branco

Electrical and Computers Engineering
Department,
University of Coimbra,
Coimbra 3030-290, Portugal
e-mail: bmbranco@gmail.com

Dariusz Asendrych

Institute of Thermal Machinery,
Częstochowa University of Technology,
Częstochowa 42-200, Poland
e-mail: darek@imc.pcz.pl

Fernando Garcia

Chemical Engineering and Forest Products
Research Centre (CIEPQPF),
University of Coimbra,
Coimbra 3030-790, Portugal
e-mail: fgarcia@eq.uc.pt

Pedro Faia

Electrical and Computers Engineering
Department,
University of Coimbra,
Coimbra 3030-290, Portugal
e-mail: faia@deec.uc.pt

Maria Graça Rasteiro

Chemical Engineering and Forest Products
Research Centre (CIEPQPF),
University of Coimbra,
Coimbra 3030-790, Portugal
e-mail: mgr@eq.uc.pt

1Present address: Chemical Engineering and Forest Products Research Centre (CIEPQPF), Chemical Engineering Department, University of Coimbra, Rua Sílvio Lima, Pólo II, Coimbra 3030-790, Portugal.

Contributed by the Fluids Engineering Division of ASME for publication in the JOURNAL OF FLUIDS ENGINEERING. Manuscript received July 25, 2016; final manuscript received February 14, 2017; published online April 24, 2017. Assoc. Editor: Francine Battaglia.

J. Fluids Eng 139(7), 071303 (Apr 24, 2017) (14 pages) Paper No: FE-16-1476; doi: 10.1115/1.4036165 History: Received July 25, 2016; Revised February 14, 2017

Eucalyptus and Pine suspensions flow in a pipe was studied experimentally and numerically. Pressure drop was measured for different mean inlet flow velocities. Electrical impedance tomography (EIT), was used to evaluate the prevailing flow regime. Fibers concentration distribution in the pipe cross section and plug evolution were inferred from EIT tomographic images. A modified low-Reynolds-number k–ε turbulence model was applied to simulate the flow of pulp suspensions. The accuracy of the computational fluid dynamics (CFD) predictions was significantly reduced when data in plug regime was simulated. The CFD model applied was initially developed to simulate the flow of Eucalyptus and Pine suspensions in fully turbulent flow regime. Using this model to simulate data in the plug regime leads to an excessive attenuation of turbulence which leads to lower values of pressure drop than the experimental ones. For transition flow regime, the CFD model could be applied successfully to simulate the flow data, similar to what happens for the turbulent regime.

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References

Figures

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Fig. 1

Typical stress–shear rate curve for fiber suspensions (adapted from Gullichsen and Härkönen [6])

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Fig. 2

Head loss curve for pulp fiber suspension flow and illustrations of different pulp flow regimes (adapted from Gullichsen and Härkönen [6] and Lundell et al. [8])

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Fig. 3

Schematic diagram of pilot rig (adapted from Ventura et al. [7])

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Fig. 4

Schematic diagram of EIT system (adapted from Zhou and Halttunen [35])

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Fig. 6

Two-dimensional axisymmetric computational domain

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Fig. 7

Rheograms and viscosity dependence on shear rate for (a) Eucalyptus pulp suspension, c = 1.50% and (b) Pine pulp suspension, c = 0.80%

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Fig. 8

Apparent viscosity and surface best fit, Eq. (1), for (a) Eucalyptus and (b) Pine pulp suspensions

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Fig. 9

Experimental pressure drop profiles. Dashed line corresponds to the pressure drop for water flow.

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Fig. 10

EIT images for Eucalyptus and Pine suspensions where the dark color (lower conductivity) corresponds to the highest and the light color (higher conductivity) to the lowest concentration of fibers

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Fig. 11

Radial profiles of mean velocity for (a) Eucalyptus pulp c = 1.01% and (b) Pine pulp c = 0.80%

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Fig. 12

Dimensionless velocity profiles for (a) Eucalyptus pulp c = 1.01% and (b) Pine pulp c = 0.80%

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Fig. 13

Radial profiles of RMS velocity for (a) Eucalyptus pulp c = 1.01% and (b) Pine pulp c = 0.80%

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