1. Progress in the development of the CO2 cooling system
Tracker Upgrade General Meeting
23 July 2010
23 July 2010
Antti Onnela & Hans Postema - CERN

2. Antti Onnela & Hans Postema - CERN
23 July 2010
Antti Onnela & Hans Postema - CERN

3. Aachen Status Report: CO2 Cooling for the CMS Tracker
Lutz Feld, Waclaw Karpinski, Jennifer Merz, Michael Wlochal
RWTH Aachen University, 1. Physikalisches Institut B
21 July MEC Upgrade Meeting

4. R & D in Aachen
Ongoing:
Gain experience with a closed recirculating CO2 system
Determine lowest operating temperature
Find out ideal operating conditions ( stable system), depending on heat load and CO2 temperature
Midterm plans:
Measurements on pipe routing inside the tracker (number of bendings, bending radius, inner diameter, ...)
Determine optimal cooling contact between cooling system and heat dissipating devices (different materials, different types of thermal connections, ...)
Contribute to final module design for tracker at SLHC
Jennifer Merz

5. System Specifications
Maximum cooling power: 500W
CO2 temperature in detector: -45°C to +20°C
Precise flow and temperature control
Continuous operation
Safe operation (maximum pressure:100bar)
Jennifer Merz

6. CO2 Test System (I) CO2-Bottle CO2-Flasche Expansion Vessel 16cm CO2
Detector
42cm
7.6cm
Heat Exchanger
19cm
Jennifer Merz

7. Electrical connections
CO2 Test System (II)
Thermistors
CO2-Bottle
CO2-Flasche
Users
panel
Electrical connections
6m stainless steel pipe, 1.7mm inner diameter
14 Thermistors along the pipe: Measurement of temperature distribution
Simulation of uniform heat load, by current through pipe ( ohmic losses)
Box for insulation
Jennifer Merz

8. Pressure Drop with Heat Load
-20°C CO2 temperature
100 W
50 W
20 W
0 W
Heat input from environment visible for small flows
Heat load affects pressure drop
The higher the heat load, the higher the pressure drop
Jennifer Merz

9. Pressure Drop: Comparison with Theory
Theory curves:
Thome model
-30°C
-20°C
-10°C
0°C
x=0.15
x=0.10
x=0.09
x=0.05
Measurement agrees with theory for high flows
Measured Δp higher for small flows
Discrepancy can be explained by creation of vapour due to heat input from environment  higher flow resistance
Jennifer Merz

10. Summary CO2 test system fully commissioned and operational
First measurements to low temperatures show: reasonable cooling power at -45°C
Pressure drop measurements: at higher temperatures (0°C, -10°C): good agreement, small heat input from environment at lower temperatures (-20°C, -30°C): worse agreement, significant heat input
Dryout Measurements: important to determine point of dryout for a given pipe layout, more measurements will be done and compared with theory
For the given layout (L=5.5m, di = 1.7mm, Φ = 50g/min) at least 70W (incl. safety factor) can be dissipated at -45°C with a pressure drop of 1.3bar
Jennifer Merz

11. Outlook
Improvements of test system ongoing: - Vacuum box for detector pipe: minimize heat input from environment - New heat exchanger: less massive, should allow faster measurements - Install dedicated pressure drop sensor: improve accuracy of measurement
Perform more measurements on pressure and temperature drop along different pipes: - Vary inner diameter and form/bending - Investigate influence of parallel piping on performance
Determine optimal cooling contact between heat dissipating devices and cooling system
Jennifer Merz

13. Progress at the large scale CO2 system,
Contents
Progress at the large scale CO2 system,
Results of the small scale CO2 system in the cryolab.

14. CO2 - Large scale system
Location in 158:
- Commissioning of the system at 25°C,
Possible mass flow rate g/s,
Run only at ambient temperature
at the moment,
Next step => accumulator to vary Tsat.
Joao Noite, Lukasz Zwalinski, Torsten Koettig

15. CO2 - Large scale system

16. Small scale system in the cryolab CERN:
CO2 – Small scale system
Small scale system in the cryolab CERN:
Test section length: 300 mm, heated part: 150 mm
Measurement of the heat transfer coefficient and pressure drop under variation of the following dependencies:
Vapor quality x
Heat flux q
Mass flux G
Saturation temperature Tsat
Jihao Wu, Daniel Helmer

17. Heat flux dependency of the heat coefficient (T=263 K, G=400 kg/m2s)
CO2 - Scanning the two-phase region
Heat flux dependency of the heat coefficient (T=263 K, G=400 kg/m2s)

18. Temperature dependency of pressure drop (q=15 kW/m2, G=300 kg/m2s)
CO2 - Scanning the two-phase region
Temperature dependency of pressure drop (q=15 kW/m2, G=300 kg/m2s)

19. Paper will be submitted to Int. Journal of Heat and Mass Transfer
Resume
Reliable test setup to determine heat transfer and pressure drop,
Measurements in the whole two phase region are done,
Influences of mass flux, heat flux and saturation temperature.
Paper will be submitted to
Int. Journal of Heat and Mass Transfer

20. Detector Technology Group
Physics Department
Detector Technology Group
Pixel CO2 Cooling Tests
João Noite

21. BPix Mock-up Testing SS 1.4 mm ID cooling tube.
5.5 m total tube length.
9x 180° tube bends, 7mm radius.
8x 54x18 mm SS heating plates.
Power from 50 to 200 W.
CO2 temperature -20°C and -30°C.
CO2 mass flow from 1 to 1.5g/s. S1 S3 S5 S7 S9 S2 S4 S6 S8
S10 P1 P4 P7
P10 P2 P5 P8
P11 P3 P6 P9
P12
João Noite

22. FPix Cooling Tube Testing
FPix Cooling Structure:
Experimental vs Theorectical:
FPix Tube L=1m
ID=1.4mm
Pmax=124W
T=-30 to 9°C
João Noite

23. BPix Carbon Fiber Support Structure – T300J vs K1100
ANSYS Calculation T300J:
BPix ¼Module:
SS Tube OD=1.6mm
ROC Simulated Power=3W
Support Structure Material:
- Carbon Fiber T300J, k=10W/m.K
- Carbon Fiber K1100, k=500W/m.K
Glue: Epoxy, k=0.35W/mK
Main observations:
K ΔT=1.35°C
T300J – ΔT=10.4°C
ANSYS Calculation K1100:
João Noite

24. Thermal Contact Test Experimental Models: Simulation Models:
João Noite

25. Thermal Contact - ANSYS Calculations
Thermal Contact Model 1:
SS Tube OD=1.6mm
Pmax=3W→2778W/m2
Epoxy: k=0.35W/m.K
Copper: k=400W/m.K
Carbon Fiber: k=10W/m.K
Main observations:
Power=3W - ΔT=13.7°C
Thermal Contact Model 2:
SS Tube OD=1.6mm
Pmax=3W→2778W/m2
Conductive Paste: k=0.35W/mK
Main observations:
Power=3W - ΔT=3.7°C
João Noite

26. Conclusions
Software of some correlations are now fully debugged an operational.
Interesting differences between calculations and measurements remain.
FPIX tube can reliably cool the requested heat load of 124 W.
ΔT over tube length < 3°C
ΔT due to HTC < 3°C
Calculations of the BPix structure show that the use of high conductive fibers gives much better performance, ΔT<2°C.
Designing the thermal interface between the tube and the carbon structure still requires much work.
João Noite

27. Antti Onnela & Hans Postema - CERN
23 July 2010
Antti Onnela & Hans Postema - CERN

28. TUPO meeting on 29 June included a discussion on pixel cooling and sensors operating temperature requirements. Input slides were prepared by Duccio Abbaneo and Frank Hartmann. Further discussions on these requirements took place now in the Cooling & Mechanics meeting. The next slides are on the sensor operating temperature and required cooling performance in the detector.

29. Assumptions
Leakage current degradation is independent of material and NIEL holds
Primary Excel worksheet based on Alberto’s recent one!
Sensor volume: V= 1.62 x x 0.03 cm3 = cm3
Vbias = 400V
500 fb-1 integrated luminosity  32 (4.6) E14 1MeVneq (see table)
I = aF x V with a = 4E-17 for 20C then T2e-(0.62eV/T_Sil*kb)
Si Current vs. T
Power vs. T (Si only, without ROC) A W
Cooling power

31. Assumption: ROC_power=2W
Power (Si+ROC) vs. T
With these assumptions (sensor surface ≈10 cm2):
If coolant temperature -20°C, DT of 20°C with 400 mW/cm2 corresponds to the critical point
i.e. the detector cooling has to remove 20 mW/(cm2 °C) or 2W/10°C.
To be safe need to require better (the green line): at least 3W/10°C.

32. Phase 1 FPIX Cooling issues
Simon Kwan for the
USCMS Mechanical Support & Cooling group
Kirk Arndt, Joe Howell, CM Lei, RL Schmitt, Terry Tope, Erik Voirin
CMS Pixel Mechanical Update July 2010

33. CMS Pixel Mechanical Update July 2010
Phase 1 Fpix Cooling Specifications - CMS Document 2333
1st draft in Feb-2008
Most recently reviewed during Phase 1 BPix/FPix engineering FNAL on Oct
CMS Pixel Mechanical Update July 2010

34. Estimated Temperature Drop
0.06 cf TPG cf Blade
~150% heat load, 7.3W per blade;
sensor: 0.4 W/cm^3; ROC: W/cm^3
Temperature Drop oC
CO2 to groove wall of ring 2
Within the half ring 3
Ring contact to sensor 7
Total (coolant to sensor) 12
This is for 150% heat load
Expect 8C for nominal load
Maximum variation from module to module on half-disk ~2C
FEA result assuming 150% heat load and
inner ring at 1oC higher than outer ring
CMS Pixel Mechanical Update July 2010

35. Cooling channel Tube Layout
Three parallel routes per half unit.
Outer-Outer
Outer-Inner
Inner (Inner-Outer and Inner-Inner in Series)
Both Outers cool a single W heat load
Inner cools a 80.3 W heat load
If only one load is applied
Two phase flow will be present in heated tubes
Single phase flow will be present in unheated tubes
11/12/2018
Erik Voirin : Terry Tope

36. CMS Pixel Mechanical Update July 2010

37. Phase 1 BPix/FPix engineering open questions
What is the minimum temperature that is safe for the detector electronics?
  suggest -25C
What is the maximum allowable rate-of-temperature change for the detector electronics?
  suggest 5C per minute
What is the minimum coolant temperature for the BPix/FPix system?
What is the expected power per 2x8 module including safety margin?
  BPix modeling uses 2.25W per 2x8 module, which appears to include only the power of the present PSI46 ROC (140mW per ROC). FPix modeling uses 3.65W per module, which is 150% of the heat load of sixteen 2x8 PSI46 ROCs plus 0.3W per 2x8 module to account for additional sources of heat, including the effects of the planned changes to the PSI46 ROC + irradiated sensor + TBM.
What is the total power required to be cooled by the Phase 1 CO2 cooling system?
Allowed range of pressure drops for the different cooling channels?
How will CO2 flow be balanced in the BPix/FPix system?
CMS Pixel Mechanical Update July 2010

38. Antti Onnela & Hans Postema - CERN
Conclusions
Several test setups, now including also large scale closed CO2 systems, fully operational and providing excellent progress in testing.
Large scale test setup in Cryolab now operational.
A lot of useful and valid data already available, and more is being acquired.
Cross-checking of results from different setups continues.
Both BPIX and FPIX detector cooling pipes are being tested.
Thermal modelling of the BPIX and FPIX structures continues, and goes to the smallest details.
Measurements on thermal interfaces (‘glue joints’) with BPIX mock-ups have started.
Good progress towards uniform pixel detector cooling specifications.
Work now required to get the essential and up-to-date documents and results available in an easily accessible way.
23 July 2010
Antti Onnela & Hans Postema - CERN