Modelling of ITER torus Vacuum system - KIT

Network Modelling of Complex Vacuum systems
Volker Hauer, Christian Day
INSTITUTE FOR TECHNICAL PHYSICS – VACUUM DEPARTMENT
KIT – University of the State of Baden-Württemberg and
National Laboratory of the Helmholtz Association
www.itep.kit.edu

Outline
1. ITERVAC Basics
2. Experimental Validation
3. Simulation of the ITER Torus Vacuum System
4. Conclusions and Outlook
5. References
2 16-19 May, 2011 64th IUVSTA Workshop on Vacuum Gas Dynamics, Leinsweiler, Germany
Volker Hauer

Basic framework of the ITERVAC code
ITERVAC baseline equation with 4 fitting parameter for dimensionless mass flow :
�� � �
�� �� � � � � ��
� � ���
Free molecular flow limit:
lim
��→� ��� � �� � �� ���
Viscous flow limit:
lim
��→� �� �� �� ������ ����� �
���� � ��� � 8�
�� � ⁄ � �� 3 16-19 May, 2011 64th IUVSTA Workshop on Practical Applications and Methods of Gas Dynamics
for Vacuum Science and Technology, May 16-19, 2011
For isothermal, isotropic Maxwellian
distribution
4 �
�� �� �
�� � � More general
approach:
��� 16 �
� � ���� �
Volker Hauer

Interpretation of the factors c i
c 1
c 2 + c 3
c 4
→ viscous flow limit (known from CFD)
→ free molecular flow limit (known from TPMC)
→ fixed parameter describing the influence of the beaming effect
The factors c i are known and can be used for predictive simulations.
Geometry clam c2 c3 c4 Circular 1.0 1.1162 0.3291 1.4
Square 1.12462 1.4862 0.5735 1.4
Rectangular (2x1) 1.02907 1.6655 0.7318 1.4
Triangular 1.2 1.9706 0.9632 1.4
Elliptic (2x1) 0.95108 1.3404 0.5054 1.4
Infinite gap 2/3 0.7133 1.1918 1.4
For short channels (L/d

Kn
1
0.1
0.01
Flow regimes - Approaches
�
0
Boltzmann
equation or
Kinetic
equations
(BGK, S)
DSMC / Test particle MC / MD /
Method of Angular Coefficients. etc
DSMC / Empirical etc.
Navier-Stokes with slip boundary conditions
ITERVAC,
LOPSTER Navier-Stokes with no slip boundary
conditions/ Euler equations
This talk
ProVac3D – A Test Particle Monte
Carlo Program For Complex
Vacuum Systems. Xueli Luo
5 16-19 May, 2011 64th IUVSTA Workshop on Practical Applications and Methods of Gas Dynamics
for Vacuum Science and Technology, May 16-19, 2011
Benchmark Problem.
Direct Simulation Monte
Carlo of Gas Flow
Through an Orifice and
Short Tube.
Stylianos Varoutis
Volker Hauer

Capabilities of ITERVAC
Provide the modeling capability for networks of channels
describe the flows in the whole range of the Knudsen number with an
acceptable (not best possible) accuracy
produce the calculation results in a short time
best for use within the process of vacuum system design
6 16-19 May, 2011 64th IUVSTA Workshop on Vacuum Gas Dynamics, Leinsweiler, Germany
Volker Hauer

ITERVAC networking
ITERVAC provides the user with all tools to build up 2D networks.
gas source
binding node
channel
ITERVAC calculates the mass flow rate through every channel depending on the
pressure of the gas source and inside the pumps.
7 16-19 May, 2011 64th IUVSTA Workshop on Practical Applications and Methods of Gas Dynamics
for Vacuum Science and Technology, May 16-19, 2011
pump
Volker Hauer

Experimental validation of ITERVAC
� Simulations with ITERVAC were performed and compared with the experimental
results of measurements with circular channels with a length to diameter ratio of
80, 60, 40, 10.
� The diameter of all test channel is 16 mm. The lengths are 1280, 963, 644 and 157
mm, respectively.
� Knudsen numbers and conductances are calculated for 273 K.
� The experiments were performed in the TRANSFLOW test rig (see presentation of
T. Giegerich at Monday).
8 16-19 May, 2011 64th IUVSTA Workshop on Practical Applications and Methods of Gas Dynamics
for Vacuum Science and Technology, May 16-19, 2011
Volker Hauer

Conductance [l/s]
Results L/d=80 and 60
12
10
8
6
4
2
0
0,00 0,01 0,10
Knudsen number
1,00 10,00
9 16-19 May, 2011 64th IUVSTA Workshop on Practical Applications and Methods of Gas Dynamics
for Vacuum Science and Technology, May 16-19, 2011
L/d=80; Experiment
l/d=80; Simulation
L/d=60; Experiment
L/d=60; Simulation
Volker Hauer

Conductance [l/s]
Results L/d=40 and 10
14
12
10
8
6
4
2
0
0,00 0,01 0,10 1,00 10,00 100,00
Knudsen number
10 16-19 May, 2011 64th IUVSTA Workshop on Practical Applications and Methods of Gas Dynamics
for Vacuum Science and Technology, May 16-19, 2011
L/d=40; Experiment
l/d=40; Simulation
L/d=10; Experiment
L/d=10; Simulation
Volker Hauer

Modelling of ITER torus Vacuum system (1)
Complex vacuum systems in ITER
11 16-19 May, 2011 64th IUVSTA Workshop on Practical Applications and Methods of Gas Dynamics
for Vacuum Science and Technology, May 16-19, 2011
Torus vacuum system
Throughputs and pressure differences are needed in all flow regimes.
Volker Hauer

Modelling of ITER torus Vacuum system (2)
12 16-19 May, 2011 64th IUVSTA Workshop on Practical Applications and Methods of Gas Dynamics
for Vacuum Science and Technology, May 16-19, 2011
The ITERVAC model includes:
� The flow path of the 54
divertor cassettes,
� 4 pumping ducts and the
connection to the 8
cryopumps,
� The flow path caused by bypass
leaks,
� The blockage by diagnostic
tools.
Volker Hauer

Modelling of ITER torus Vacuum system (3)
Maximum Throughput [Pa m³/s]
Resulted maximum throughput for deuterium:
4500
4000
3500
3000
2500
2000
1500
1000
500
0
Torus pumps
Plasma
0 2 4 6 8 10 12
Divertor dome pressure [Pa]
13 16-19 May, 2011 64th IUVSTA Workshop on Practical Applications and Methods of Gas Dynamics
for Vacuum Science and Technology, May 16-19, 2011
Input parameter:
� divertor pressure 1-10 Pa
� deuterium (single gas)
� temperature 420 K
Volker Hauer

Conclusions and Outlook
� In all cases, a good agreement is observed between corresponding numerical and
experimental results for specific range of Knudsen number. The best agreement
was found for the channel with L/d=10.
� The average relative error is of the order of 20%.
� The largest discrepancies between experimental and numerical results are
observed in laminar flows, whereas in the free molecular regime the smallest
differences are found.
� The present work will be extended to the study of different cross sections and in the
intermediate length range of 5< L/D h

References (1)
Proceedings:
1. C. Day, V. Hauer, G. Class, D. Valougeorgis, and M. Wykes, “Development of a
simulation code for ITER vacuum flows”, IAEA Fusion Energy Conference,
Chengdu, China (2006).
2. S. Varoutis, V. Hauer, C. Day, “Investigation of gas flows in fusion reactors”. AVS
56th International Symposium, San Jose-California, USA (2009).
3. S. Varoutis, V. Hauer, C. Day, S. Pantazis and D. Valougeorgis, “Experimental and
numerical investigation in flow configurations related to the vacuum systems of
fusion reactors”. 9th International Symposium on Fusion Nuclear Technology,
Dalian, China (2009).
15 16-19 May, 2011 64th IUVSTA Workshop on Practical Applications and Methods of Gas Dynamics
for Vacuum Science and Technology, May 16-19, 2011
Volker Hauer

References (2)
Journals:
4. S. Varoutis, S. Naris, V. Hauer, C. Day and D. Valougeorgis, “Experimental and
computational investigation of gas flows through long channels of various cross
sections in the whole range of the Knudsen number”, JVSTA, 27 (1), 89-100
(2009).
5. S. Varoutis, V. Hauer, C. Day, S. Pantazis and D. Valougeorgis, “Experimental
and numerical investigation in flow configurations related to the vacuum
systems of fusion reactors”, FED, 85, 1798–1802 (2010).
6. V. Hauer, Chr. Day, “Conductance modelling of ITER vacuum systems”, FED, 84,
903–907 (2009).
16 16-19 May, 2011 64th IUVSTA Workshop on Practical Applications and Methods of Gas Dynamics
for Vacuum Science and Technology, May 16-19, 2011
Volker Hauer