Transcript Brooks-CS Thermal Analysis Status.ppt

CS Thermal Analysis Status
• Heating and Cooling of CS During Normal
Operation - SN & DN Operation
– Overall Heat Balance
– Heating of Center Stack
• First Cut Thermal-Stress Analysis of CS
• Study of Impact of CS Tile Size on Thermal Stress
Heating and Cooling of CS
During Normal Operation
• ANSYS 2D Axisymmetric Model
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CS radiatively Cooled to IBDhs, OBD, PP and VV
CS assumed perfectly insulated from OH & PF’s
CS Tiles assumed in perfect contact with Inconel Casing
IBDhs, OBD, PP and VV actively cooled
• Equivalent film coefficient used – need to review and verify for new design
• For CS, only modest coiling assumed at IBDhs
• Single Null (SN) and Double Null (DN) modes
– No Natural Divertor Mode defined in GRD (was worse case in original
design)
• CS Surface emissivity varied
– 0.7 for Graphite (without Lithium)
– 0.3 for Lithium Coated Graphite (best guess)
• 14 MW, 5s pulse, 1200s rep rate
– Largest Power Fraction to IBDhs
– ~1/3 Power Uniformly Radiated to All exposed Surfaces
Applied Heat Fluxes
Average Heat removal rate thru Cooling Systems (IBDhs, OBD, PP and VV)
should total 14e6*5/1200 = 58.3 kW after fully ratcheting (see plots)
Question: The GRD requirement for the CSFW is fairly modest.
Are there scenarios not included here which could lead to
higher heat fluxes?
IBDVS
IBDHS
CSAS
CSFW
End of 10th Pulse
(Not yet fully
ratcheted)
CS Inconel Casing
Tavg = 342 C
Thermal
Equilibration
Within Tile
Cooling
CS Inconel Casing
Tavg = 455 C
CS Inconel Casing
Tavg = 286 C
CS Inconel Casing
Tavg = 370 C
Summary of Heating in CS Inconel Casing
Observations
• Highest Tile temperatures at IBDhs where largest
fraction of Power is deposited
– SN much higher than DN as expected
• PP Cooling picks up largest fraction of total heat
with VV, OD & ID picking up comparable smaller
amounts
– Variation of heat load to cooling systems* not
significantly different for scenarios analyzed
• Highest Bulk Heating of CS Inconel Casing due
to DN Operation (342C at e=.7, 455C at e =.3)
*For SN all IBDhs heat load to lower cooling system
First Cut Thermal-Stress Analysis of CS
• Fully Ratcheted Temperature Distribution from Previous
Thermal Analysis of Single Null (highest tile temperatures)
with emiss=.7 used
• CS Tile thermal stress only
– Assuming ATJ Structural Properties (first cut - not temperature
dependent)
– Initial Run as 2D axisymmetric, followed by 3D cyclically
symmetric
– Compares single (very) large tile to segmented tile (at Inboard
Divertor Horizontal Section)
• CS Casing thermal stress only
– Assumes Inconel 625 Properties (first cut - not temperature
dependent)
– Model includes CS Casing, VV and Connecting Bellows
Temperature Distribution
Following Fully
Ratcheted Pulse
Graphite Only
Axisymmetric
No Split
Axisymmetric
With Split
Cyclically symmetric
No Split
Cyclically symmetric
With Split
Temperature Distribution
Following Fully
Ratcheted Pulse
(At Max CS Average Temp)
Vacuum Boundary Only
Observations
• Segmenting of tile Poloidally has modest affect
(slightly lower Seqv) but segmenting toroidally
leads to higher stresses.
• Tile Stress levels (without including temperature
dependency on Properties and allowables) show
max stresses ~1/2 yield
• Inconel Casing Stress levels are also ~1/2 yield
Study of Impact of CS Tile Size
on Thermal Stress
• Simplified Geometry – Segmented Cylinder
• ATJ Graphite Properties assumed
• 1 MW/m2 Heat Flux for 5 sec Pulse
– Much Higher than GRD Spec 0.1-0.2 MW/m2
• Freely supported tile (ie unconstrained)
– Stresses from Thermal Gradients
• Results show stresses increase significantly with
tile size
Results
Millions
CS Tile Thermal Stress vs Tile Size
1 MW/m2 for 5 sec
2.5
2
1.5
Sx+
Sx-
Stress, Pa
1
Sy+
Sy-
0.5
0
Sz+
SzSxy
-0.5
-1
Syz
Sxz
Seqv
-1.5
-2
-2.5
10
20
30
40
50
Angular extent, deg, of ~square tile
Results show stresses increase significantly with tile size