CFD modelling of multiphase flows in oil and gas, chemical and process industries Simon Lo 13/09/2011
CFD modelling of multiphase flows in oil and gas,
chemical and process industries
Simon Lo 13/09/2011
Contents
• Shell-&-tube heat exchanger – flow, thermal & stress
• T-junction, thermal sleeve – thermal stripping, FSI
• Gas-liquid flow in pipeline and riser – sever slugging
• STAR-OLGA coupling – 1D + 3D modelling
• Offshore platform – wave impact, lifeboat launch
• Process equipment – mixing vessel, particle conveying
EGR cooler: Conjugate Heat Transfer Model
• 148 tubes
• 3.5 million cells model
Steel
570,000 cells
Tube-side:
EGR Gas
1.8 million cells
Shell-side:
Coolant
1.2 million cells
Computed Mass Flux Through the EGR Tubes
0.509 0.521 0.531 0.507
0.540 0.545 0.519 0.514 0.522 0.505 0.480
0.558 0.571 0.558 0.587 0.575 0.554 0.526 0.478 0.478 0.461
0.560 0.594 0.568 0.681 0.722 0.732 0.686 0.595 0.503 0.456 0.449
0.601 0.636 0.692 0.857 0.876 0.854 0.794 0.656 0.504 0.439 0.445
0.567 0.659 0.773 0.883 0.916 0.926 0.915 0.892 0.816 0.674 0.433 0.428 0.435
0.641 0.782 0.886 0.940 0.941 0.940 0.928 0.896 0.819 0.396 0.433
0.608 0.711 0.868 0.920 0.943 0.951 0.935 0.921 0.881 0.786 0.597 0.444 0.440
0.648 0.795 0.896 0.935 0.945 0.935 0.928 0.904 0.848 0.703 0.525 0.439
0.566 0.687 0.826 0.910 0.928 0.935 0.927 0.907 0.867 0.764 0.594 0.453 0.443
0.578 0.687 0.827 0.887 0.901 0.911 0.901 0.863 0.780 0.628 0.474 0.442
0.569 0.648 0.779 0.836 0.860 0.827 0.771 0.632 0.493 0.450
0.512 0.596 0.688 0.705 0.723 0.748 0.702 0.572 0.478 0.437
0.527 0.604 0.638 0.622 0.580 0.509 0.454
0.509 0.510 0.496 0.476
Total Mass Flow: 0.244944 kg/secPercent of Total Flow
Key Results: Coolant Boiling
• Two regions where boiling of
the coolant might occur
(Shown as red regions).
1. Close to the fire plate, due
to high metal temperatures
and lack of circulation.
2. Behind the first baffle, due
to lack of circulation.
Design Assessment of an EGR Cooler
Integrated CFD/FEA Methodology
• CFD Analysis Used to Determine:
• Heat Transfer Coefficients
• Core Pressure Drop Characteristics
• Flow Distributions in Manifolds and Core
• FEA Analysis Used To Determine:
• Transient Temperatures
• Transient Thermal Stresses
• Vibratory Stress
• CFD Analyses performed using STAR-CD
• FEA Analyses performed using ANSYS
CFD Exhaust Gas Models
Exhaust Gas model used to
develop manifold heat transfer
boundary conditions, and
develop mass flow split in
core. Detailed tube model
captures local effects.
FEA Thermal Analysis – Gas Boundary Conditions
Start of Spiral
End of Spiral
Entrance Effect
CFD
FEA
Gas BC‟s mapped from CFD to FEA.
Detailed pipe model results used for
tube surfaces. Mass flow split
obtained from CFD as well. Core
gas temperatures developed through
use of pipe flow network
FEA Thermal Analysis Coolant Boundary Conditions
Coolant BC‟s mapped from CFD to FEA.
Boiling effects considered in FEA.
FEACFD
Thermal Analysis Transient Temperatures
Transient thermal run simulates
test cycle. These temperatures
provide the basis for the thermal
stress analysis.
Results are tracked to obtain the
time points that produce the largest
thermal gradients.
Thermal Stress Analysis
Thermal strain ranges are calculated at each
location, and between all time points. This
determines the greatest strain range experienced
for all locations.
Zeses Karoutas et al. Westinghouse Electric Company
Top Fuel 2010, Orlando, Florida, September 26-29, 2010
AP1000 PWR - Virtual Simulators
International Benchmark – OECD T junction
23S.T. Jayaraju, E.M.J. Komen: Nuclear Research and Consultancy Group (NRG), Petten,
The Netherlands
T-junction Benchmark Results – Blind test
Wall Resolved LES
normalized flow profiles at 2.6 diameters
downstream of the mixing zone
normalized flow profiles at 1.6 diameters
downstream of the mixing zone
S.T. Jayaraju, E.M.J. Komen: Nuclear Research and Consultancy Group (NRG), Petten, The Netherlands
Thermal sleeve failed after 40 days operation.
Vibration issues.
Fluid-structure interaction (FSI) modelling:
Structure modeled totally within STAR-CCM+
Fluid grid morphed to conform
Implicit fluid/solid coupling
Thermal Sleeve
Sever slugging in riser, Uni of Cranfield, UK
4 inch riser
55 m pipeline
10.5 m
Riser top
Riser base
Riser DP = Pbase - Ptop
50 100 150 200 250 300 3500
0.2
0.4
0.6
0.8
1
Flow time t, s
Ris
er
DP
, bar
Experiment
Star-CD-1
Star-CD-2
Dynamic forces on pipe elbow in slug flow
Mass flux, velocity and density of each phase
Pressure and temperature
Flow direction
Model the long pipe
using OLGA with slug
tracking
Model pipe elbow using STAR-CCM+
Pressure variation due to slug flow pass elbow
Gas volume fraction Pressure on the outer part
Note the passing of liquid
slug in “blue”.
Note the increase in pressure as
liquid slug passes.
Resultant force and force
components on the inner part
Forces on the inner part
5 6 7 8 9 10 11 12 13 14 15-30
-20
-10
0
10
20
30
Flow time t, s
Forc
e o
n t
he inner
wall
FI,
N
5 10 150
0.2
0.4
0.6
0.8
1
Liq
uid
hold
up H
L in t
he b
end
FRI
: Resultant force of FxI
and FyI
FxI
: x component
FyI
: y component
FzI
: z component
Direction change
Comparison
Coupling model Experiment
Slug frequency (Hz) 0.5 0.5
Slug velocity (m/s)slug front: 2.8 to 3.6
slug tail: 3.0 to 3.53.6
Peak force on bend (N) 44 to 54 40 to 60
Maximum force on bend (N) 54 60
In industrial design with safety factor „2‟: maximum force 141 N
EXXON-MOBIL SLUG CATCHER
• Tanks 45 m long, 3 m diameter.
• Time scale large (2 hours)
• CFD Model: 2.2 Million cells.
Inlet
Gas Outlets
Oil Outlets
Mixing of viscous liquids
• An example of a mixer for highly viscous liquids, with small gaps
between moving parts whose paths cross during rotation.
Discrete Element Method (DEM)
• Simple conveyor problem
– Non-spherical particles: 3 sphere composite particles
– Conveying belt: Wall velocity boundary condition
Outlook – Geometry resolution
• Size of CFD model:
– 1 billion cells => frontier
– 100 million cells => large
– 10 million cells => average
– 1 million cells => small