cfd modelling of the flow inside an lc refiner
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CFD Modelling of the Flow Inside an LC Refiner
Dariusz Asendrych, Grzegorz KondoraCzęstochowa Univ. of Technology, Poland
CFD Modelling of the Flow Inside an LC RefinerCOST FP1005 / SIG 43 meeting, 24-26.X.2012, Trondheim 1
A joint meeting
COST Action FP1005Fibre suspension flow modelling - a key for innovation
& competitiveness in the pulp & paper industry
ERCOFTAC SIG 43Fibre suspension flows
� Introduction / Motivation
� Numerical model� Simplified / full geometry � Boundary conditions� Governing equations
� Results
Outline
CFD Modelling of the Flow Inside an LC RefinerCOST FP1005 / SIG 43 meeting, 24-26.X.2012, Trondheim 2
� Results
� Simplified geometry - Diverging grooves� Full geometry - General flow pattern
� Summary / Perspectives
plate disc refiner Geometry – assumptions
simplified
• neglected housing ⇒ axisymmetric outlet (instead of point outlet)
• neglected axial part of inlet, radial inlet applied
LC refiner
CFD Modelling of the Flow Inside an LC RefinerCOST FP1005 / SIG 43 meeting, 24-26.X.2012, Trondheim 3
applied• periodicity of discs geometry - single-
segment (30 degrees of angular extent -1/12)
full
• 12 segments• housing• single-pipe outlet
typical refiner filling
Boundary conditions
CFD Modelling of the Flow Inside an LC RefinerCOST FP1005 / SIG 43 meeting, 24-26.X.2012, Trondheim 4
� simplified filling
� inlet - VELOCITY INLET
� outlet - PRESSURE OUTLET
�PERIODIC B.C.
�INTERFACE for sliding meshes
• geometry and mesh - GAMBIT
• mesh: 6 / 24 mln cells
• FLUENT 6.3 / 13
• pulp suspension treated as a single-phase continuum (N-S, continuity)
• flow character assumed to be laminar (confirmed by simulation results)
• pulp modelled as either Newtonian or non-Newtonian fluid
Governing equations
UUUU 2p
t∇+∇−=∇⋅+
∂∂
ρµ
ρ
CFD Modelling of the Flow Inside an LC RefinerCOST FP1005 / SIG 43 meeting, 24-26.X.2012, Trondheim 5
• fibre-fibre and fibre-wall interactions are neglected - main goal was to analyze the LC refining hydraulics
or
0=∇U
t∂ ρρ
( )γf=µwhere - rate of deformation tensorγ
const=μ
softwood pulp, Cm = 4%, fibre lenght = 1400 µm, diameter = 26 µm
Newtonian fluid - constant apparent viscosity
Pulp material properties
CFD Modelling of the Flow Inside an LC RefinerCOST FP1005 / SIG 43 meeting, 24-26.X.2012, Trondheim 6
ln(l/d) = 3,986 ln(µr) = 5,91 µr = 370
µpulp = µr · µwater = 370 · 0,001003 = 0,371 Pa·s
source:Radoslavova, Silvy, Roux, 1996,,TAPPI Paper makers Conf., Philadelphia
reverse flows in stator disc
⇓
enhanced internalcirculation
General flow pattern
CFD Modelling of the Flow Inside an LC RefinerCOST FP1005 / SIG 43 meeting, 24-26.X.2012, Trondheim 7
αdiv = 0.0 deg
αdiv = 0.25 deg
Diverging grooves
CFD Modelling of the Flow Inside an LC RefinerCOST FP1005 / SIG 43 meeting, 24-26.X.2012, Trondheim 8
αdiv = 0.50 deg
intensification of reverse flow
Diverging grooves
CFD Modelling of the Flow Inside an LC RefinerCOST FP1005 / SIG 43 meeting, 24-26.X.2012, Trondheim 9
Diverging grooves
CFD Modelling of the Flow Inside an LC RefinerCOST FP1005 / SIG 43 meeting, 24-26.X.2012, Trondheim 10
Diverging grooves
CFD Modelling of the Flow Inside an LC RefinerCOST FP1005 / SIG 43 meeting, 24-26.X.2012, Trondheim 11
• mass flux exiting stator grows
• power consumption decreases
Full refiner
simulation
CFD Modelling of the Flow Inside an LC RefinerCOST FP1005 / SIG 43 meeting, 24-26.X.2012, Trondheim 12
Full refiner
simulation
•• housinghousing includedincluded
•• pipepipe outletoutlet
•• 12 12 segmentssegments
outlet pipe
outlet
Full refiner geometry model
CFD Modelling of the Flow Inside an LC RefinerCOST FP1005 / SIG 43 meeting, 24-26.X.2012, Trondheim 13
collectoroutlet pipe
inlet
Velocity magnitude
rotor
stator
CFD Modelling of the Flow Inside an LC RefinerCOST FP1005 / SIG 43 meeting, 24-26.X.2012, Trondheim 14
Pressure distribution
p[bar]
7
6
5
rotor
stator
CFD Modelling of the Flow Inside an LC RefinerCOST FP1005 / SIG 43 meeting, 24-26.X.2012, Trondheim 15
4
3
2
1
0
Pressure distribution
5
4
3
2
p[bar]
5
r*
0
1
CFD Modelling of the Flow Inside an LC RefinerCOST FP1005 / SIG 43 meeting, 24-26.X.2012, Trondheim 16
1
r* [-]
5
4
3
2
1
p[bar]
Pressure distribution
p[bar]
7
6
5
gap
CFD Modelling of the Flow Inside an LC RefinerCOST FP1005 / SIG 43 meeting, 24-26.X.2012, Trondheim 17
4
3
2
1
0
LC refiner flow model - Fox et al.
CFD Modelling of the Flow Inside an LC RefinerCOST FP1005 / SIG 43 meeting, 24-26.X.2012, Trondheim 18
Fox, T.S., Brodkey, R.S. Nissan, A.H., 1979, TAPPI J., 62 (3)
Pressure distribution - CFD vs Fox et al.
exit region
CFD Modelling of the Flow Inside an LC RefinerCOST FP1005 / SIG 43 meeting, 24-26.X.2012, Trondheim 19
0 1 2 3 4 5 6 7 [bar]
Mass flux at filling outlet
CFD Modelling of the Flow Inside an LC RefinerCOST FP1005 / SIG 43 meeting, 24-26.X.2012, Trondheim 20
Mass flux at filling outlet
full refiner single-segment refiner
2
1
CFD Modelling of the Flow Inside an LC RefinerCOST FP1005 / SIG 43 meeting, 24-26.X.2012, Trondheim 21
0
-1
-2
Flow reversals in stator
CFD Modelling of the Flow Inside an LC RefinerCOST FP1005 / SIG 43 meeting, 24-26.X.2012, Trondheim 22
full refiner
Simplified geometry model
• qualitative agreement with experimental observation - adequate numerical model
• divergent grooves:
� modified pressure distribution and enhanced flow reversals
� no energy penalty - improved flow quality
Summary / Perspectives
Full geometry model
• circulation / exit regions - analogy to Fox et al.
CFD Modelling of the Flow Inside an LC RefinerCOST FP1005 / SIG 43 meeting, 24-26.X.2012, Trondheim 23
• circulation / exit regions - analogy to Fox et al.
• existence of the backflows in the stator
• mass flow rate distributions stongly non-uniform and rotor position dependent
General
• no fibres included...
• CFD can really help - useful tool in process optimisation
• time consuming simulations
• ongoing simulations / data processing for varying conditions
Thank You for Your Attention
CFD Modelling of the Flow Inside an LC RefinerCOST FP1005 / SIG 43 meeting, 24-26.X.2012, Trondheim 24
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