slawomir pietrowicz, bertrand baudouy cea/irfu/sacm january 20, 2011, saclay
DESCRIPTION
EuCARD -HFM ESAC review of the high field dipole design Cooling , heat transfer and cool-down issues. Slawomir Pietrowicz, Bertrand Baudouy CEA/IRFU/SACM January 20, 2011, SACLAY. Outline. Modeling of thermal process in the magnet during ramp rate – 2 D steady state model - PowerPoint PPT PresentationTRANSCRIPT
EuCARD-HFM ESAC review of the high field dipole design
Cooling, heat transfer and cool-down issues
Slawomir Pietrowicz, Bertrand BaudouyCEA/IRFU/SACM
January 20, 2011, SACLAY
1
Outline
▫Modeling of thermal process in the magnet during ramp rate – 2 D steady state model◦Geometry and applied mesh;
◦Properties of the materials;
◦Results - maximum temperature rise as a function of heat load.
▫Modeling of cool-down process – 2 D transient model◦ Indirect method from 300 k to 20 K – cool-down through cooling tubes
− Assumptions and scenarios of cool-down used during calculations;
− Results – maximum temperature rise as a function of time;
◦Direct method from 20 K to 4.2 K – direct filling with helium;− Scenario of cool-down used during calculations;
− Results - maximum temperature rise as a function of time;
◦Estimation of maximum temperature rise of cooling helium.
▫Summary
2
▫Modeling of thermal process in the magnet during ramp rate– 2 D steady state model◦Geometry and applied mesh;
◦Properties of the materials;
◦Results - maximum temperature rise as a function of heat load.
▫Modeling of cool-down process – 2 D transient model◦ Indirect method from 300 k to 20 K – cool-down through cooling tubes
- Assumptions and scenarios of cool-down used during calculations; - Results – maximum temperature rise as a function of time;
◦Direct method from 20 K to 4.2 K – direct filling with helium; - Scenario of cool-down used during calculations; - Results - maximum temperature rise as a function of time;
◦Estimation of maximum temperature rise of cooling helium.
▫Summary
3
Modeling of thermal process in the magnet during ramping process – 2 D steady state model
4
Geometry and boundary conditions applied during simulations
Physical model
• model of heat transfer used during simulations (steady state):
Assumptions
• Two types of boundary conditions:
1. Constant temperature on walls (red lines);
2. Symmetry (yellow lines);
• Thermal conductivity as function of temperature;
• Perfect contact between solid elements;
• 1 W, 5 W and 10 W dissipated in conductors. For those values the homogenous spreads of heat sources are used;
• Calculations are carried out also for CUDI model (AC loss due to ISCC losses, non-homogenous spreads)
• Calculations are performed for two bath (helium) temperature 1.9 K and 4.2 K
Constant temperatureSymmetry
Modeling of thermal process in the magnet during ramp rate – 2 D steady state model
5
Details of applied mesh
Mesh – 715 k of structural elements
Modeling of thermal process in the magnet during ramp rate – 2 D steady state model
6
Source:Cryocomp Software v 3.06Metalpak Software v 1.00
0 50 100 150 200 250 3000.01
0.1
1
10
100
1000
10000
Iron Aluminium Alloy 7075-T6 Phosphor bronze 304 Stainless SteelTi-6Al-4V Nb3Sn G10 AluminiumPolyamide, PA6
Temperature, K
Th
erm
al
Co
nd
ucti
vit
y,
W/m
K
Modeling of thermal process in the magnet ramp rate – 2 D steady state model
7
The temperature contour map and localization of maximum temperature rise1.9 K 4.2 K
1 W
5 W
10 W
CUDI Modelaverage 0.2 W
Hom
ogen
ous
spre
ad
of h
eat d
issi
pati
on
Modeling of thermal process in the magnet during ramp rate – 2 D steady state model
8
Temperature rise in the magnet as a function of unit heat load
Heat load
Name Unit Value
Critical temperature
rise
Total W 0,2 1,0 5,0 10,0
Unit W/m 0,1 0,5 2,6 5,3
Volumetric W/m3 4,3 21,8 108,9 217,7
Maximum temperature
rise
@ 1,9 K 0,231 1,053 2,906 3,951 6,1
@ 4,2 K 0,066 0,354 1,344 2,197 3,8
CUDI Model Homogenous model
Maximum temperature difference in magnet at different temperature and heat load
0 1 2 3 4 50
0.5
1
1.5
2
2.5
3
3.5
4
4.5
1.9 K
Heat load, W/m
Maxi
mum
tem
pera
ture
ris
e,
K
LHC Upgrade
▫Modeling of thermal process in the magnet during ramp rate– 2 D steady state model◦Geometry and applied mesh;
◦Properties of the materials;
◦Results - maximum temperature rise as a function of heat load.
▫Modeling of cool-down process – 2 D transient model◦ Indirect method from 300 k to 20 K – cool-down through cooling tubes
- Assumptions and scenarios of cool-down used during calculations; - Results – maximum temperature rise as a function of time;
◦Direct method from 20 K to 4.2 K – direct filling with helium; - Scenario of cool-down used during calculations; - Results - maximum temperature rise as a function of time;
◦Estimation of maximum temperature rise of cooling helium.
▫Summary
9
Modeling of cool-down process – 2 D transient model – indirect cooling
10
Assumptions:
8 cooling elements (tubes) for magnet are proposed (2 per quarter) on external shell;
Cp and k are function of temperature, Cp(T), k(T);
Helium is treated as solid domain (it could be changed in future and buoyancy flow can be modeled);
4 scenarios (1.5, 2, 3 and 4 days) of cool-down from 300 K to 20 K are considered;
The cooling tubes are replaced by temperature evolution in time according to the following graph;
0 0.5 1 1.5 2 2.5 3 3.5 410
60
110
160
210
260
310
2 days3 days4 days
Time, days
Tem
pera
ture
, K
1 1 1
2 2 23 3 34 4 4
The details of cooling scenarios I II III IV
1. Cooling step 300 K to 80 K 3 days 2 days 1days 0,5 day
2. Electrical integrity test at 80 K 6 hour 6 hour 6 hour 6 hour
3. Cooling step 80 K to 20 K 12 hour 12 hour 12 hour 12 hour
4. Electrical integrity test at 20 K 6 hour 6 hour 6 hour 6 hour
Total 4 days 3 days 2 days 1,5 dayEvolution of temperature on the cooling elements
Cooling tubes
helium
Symmetry
Sym
met
ry
Adiabatic
Adiabatic
Ad ia
bat ic
Time
Te
mp
era
ture
helium
Symmetry
Sym
met
ry
Adiabatic
Adiabatic
Ad ia
bat ic
1111
Modeling of cool-down process – 2 D transient model -indirect cooling
Source:Cryocomp Software v 3.06Metalpak Software v 1.00
0 50 100 150 200 250 3000
200
400
600
800
1000
1200
1400
1600
1800
2000
Iron Phosphor bronze 304 Stainless Steel Ti-6Al-4VNb3Sn G10 Aluminium Polyamide, PA6
Temperature, K
Th
erm
al
Ca
pa
cit
y,
J/k
g K
Cycle of cool-down (every 8 hours for 4 days)12
Modeling of cool-down process – 2 D transient model - indirect cooling
Modeling of cool-down process – 2 D transient model - indirect cooling
13
Evolution of maximum DT within the magnet structure
0 10 20 30 40 50 60 70 80 900.0
10.0
20.0
30.0
40.0
50.0
60.0
0
50
100
150
200
250
300
1.5 days2 days3 days4 daysMaximumPower (Maximum)cooling function 1.5 dayscooling function 2 days
Time, h
Ma
xim
um
te
mp
era
ture
diff
ere
nce
, K
Te
mp
era
ture
of
coo
ling
fu
nct
ion
, K
14
Geometry and boundary conditions applied during simulations
After indirect cool-down to 20 K via external tubes, direct cooling method from 20 K to 4.2 K is applied e.g. helium is flowing directly to the structure from the bottom of magnet (vertical configuration).
The first type of boundary conditions is used e.g. the temperature on the walls (read lines). The temperature changes in time according to graph.
0 1 2 3 4 50
5
10
15
20
Time, hTem
pera
ture
on w
alls,
K
Modeling of cool-down process – 2 D transient model - direct cooling
Changing temperatureSymmetry
15
Evolution of maximum DT in the magnet structure during direct cool-down
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 50
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0.5
0
2
4
6
8
10
12
14
16
18
20
after 1.5 days
after 3 days
after 4 days
after 2 days
Cooling function
Time of direct cool-down, h
Maxi
mum
tem
pera
ture
diff
ere
nce
in
magnet,
K
Modeling of cool-down process – 2 D transient model - direct cooling
16
Available compressor with maximum capacity 100 g/s of cooling helium at 16 bars and 80 K (SM18 at CERN) and DTmax compr= THe Outlet - THe Inlet = 50 K.
The mass flow rate of cooling helium can be calculated from the equation:
0 10 20 30 40 50 60 70 80 90 1000
2,000
4,000
6,000
8,000
10,000
12,000
14,000
16,000
18,000
1.5 days2 days3 days4 days
Time, hour
Tota
l heat,
WModeling of cool-down process – 2 D transient model
– mass flow rate of cooling helium
The total heat which has to be removed from whole magnet during cool-down via cooling tubes. The data obtained from numerical simulations.
�̇�𝐻𝑒=�̇�𝑡𝑜𝑡𝑎𝑙
h𝐻𝑒𝑜𝑢𝑡𝑙𝑒𝑡−h𝐻𝑒𝑖𝑛𝑙𝑒𝑡 m is limited by capacity of compressor (100 g/s)
inlet enthalpy of cooling helium for Tin = 80 K, p = 16
bars
outlet enthalpy of cooling helium for Tout = 80 K + DT, p = 16 bars
17
Modeling of cool-down process – 2 D transient model - mass flow rate of cooling helium
Time of total cool-down
Maximum heat
Maximum temperature
rise of cooling helium
kW K
1.5 days 17.1 32,86 < DTmax compr
2 days 9.1 17,34
3 days 4.7 9,06
4 days 3.2 6,09
1.5 2 2.5 3 3.5 405
101520253035
Time of cool-down, days
Maxim
um
tem
pera
ture
ri
se o
f co
oling h
elium
, K
The changes of maximum temperature rise of cooling helium for different scenarios
The changes of maximum temperature rise of cooling helium for different scenarios
▫Modeling of thermal process in the magnet during ramp (heat dissipation) rate– 2 D steady state model◦Geometry and applied mesh;
◦Properties of the materials;
◦Results - maximum temperature rise as a function of heat load.
▫Modeling of cool-down process – 2 D transient model◦ Indirect method from 300 k to 20 K – cool-down through cooling tubes
- Assumptions and scenarios of cool-down used during calculations; - Results – maximum temperature rise as a function of time;
◦Direct method from 20 K to 4.2 K – direct filling with helium; - Scenario of cool-down used during calculations; - Results - maximum temperature rise as a function of time;
◦Estimation of maximum temperature rise of cooling helium.
▫Summary
18
Summary
▫2D numerical model based on FVM (Finite Volume Method) has been developed in ANSYS CFX Software. The steady and unsteady simulations have been performed.
▫For steady simulations: the maximum temperature rises are smaller than critical temperature.
▫For transient simulations: 1. The simulations show that maximum temperature differences in magnet
structure are varying from 10 K to 60 K.
2. The most critical time during cool-down is first 14 hours (by the reason of mechanical constraints).
3. The maximum temperature rise during direct cool-down is relatively small 0,45 K in comparison with indirect cool-down method.
4. One compressor is sufficient for indirect cool-down with helium mass flow rate of 100 g/s at 16 bars, 80 K for all scenarios.
19
Summary
Future plans
▫Develop the numerical model to 3 D.
▫Simulate the quench evolution in magnet with different localization of quench heaters.
▫Extend the calculations to superfluid and boiling helium.
20