“Heat Transfer Capacity of the 2S Module Support Insert”

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2S Module meeting, 24 September 2012Studies on module support inserts

Refers to work by Riikka Häsä, Helsinki Institute of Physics, summer student at CERN 2012

2S module meeting, 24 September 2012, indico: 208421

Antti Onnela, CERN

“Heat Transfer Capacity of the 2S Module Support Insert”

“Mechanical Strength of the 2S Module Insert – Cooling Pipe Joints”Reports available in https://espace.cern.ch/Tracker-Upgrade/2S-Module/Shared%20Documents/Forms/AllItems.aspx

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“Heat Transfer Capacity of the 2S Module Support Insert”


Antti Onnela, CERN

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Module support insert thermal analysis


Antti Onnela, CERN

Insert material properties usedAluminium Thermal conductivity, k 174 W/mK

Epoxy Thermal conductivity, k 0.2 W/mKStainless steel Thermal conductivity, k 15.1 W/mK

CO2 Heat transfer coefficient, h 10 000 … 20 000 W/m2K

Module power estimatesPower of a complete module [W]

2x8 CBCs 2 concen-trators

L-P GBT GBTIA GBLD Power converter

TOTAL

1.2 0.36 0.5 0.1 0.2 0.4 2.8Power per support insert next to service board [W]

0.3 0.18 0.25 0.05 0.1 0.2 1.08Power per support insert opposite to service board [W]

0.3 0.3

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Support insert geometry

Cooling pipe dimension used: 2.2 mm OD, 2.0 mm ID (TOB single-sided rod type)

In addition, a ‘cap’ glued to surround the cooling pipe


Antti Onnela, CERN

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Cases analysed:1. 25 mm long insert, h = 10 000 W/m2K 2. 25 mm long insert, h = 20 000 W/m2K3. 30 mm long insert, h = 10 000 W/m2K4. 30 mm long insert, h = 20 000 W/m2K5. 35 mm long insert, h = 10 000 W/m2K6. 40 mm long insert, h = 10 000 W/m2K


Antti Onnela, CERN

1 2 3 4 5 6

0.00

1.00

2.00

3.00

4.00

5.00

6.00

PipeCO2

InsertGlue

Total

5.40

4.915.21

4.785.11 5.06

PipeCO2InsertGlueTotal

ΔT /

°C

Case Pipe CO2 Insert Glue Total1 0.10 1.54 2.57 1.78 5.402 0.11 0.85 2.57 1.95 4.913 0.10 1.46 2.56 1.68 5.214 0.11 0.81 2.55 1.87 4.785 0.09 1.41 2.55 1.64 5.116 0.09 1.39 2.55 1.61 5.06

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Cases analysed:1. 25 mm long insert, h = 10 000 W/m2K 2. 25 mm long insert, h = 20 000 W/m2K3. 30 mm long insert, h = 10 000 W/m2K4. 30 mm long insert, h = 20 000 W/m2K5. 35 mm long insert, h = 10 000 W/m2K6. 40 mm long insert, h = 10 000 W/m2K

Conclusions:• ∆T over the assembly is ~ 5 ˚C in all analysed cases

– Not excellent, as ∆T within the module is estimated to be 5-7 ˚C – Reaching ∆T of 10 ˚C between module and coolant is difficult.

• CO2 heat transfer coefficient (h) has a significant impact– More detailed studies needed to calculate h for different locations and loads along the rod,

as well as finding the best suiting pipe diameter.• Insert has a significant impact, ~ 50% of the ∆T

– Increasing the insert length (mass) does not help much– Shortening the distance between module and cooling pipe would help, but is

geometrically difficult / impossible.– Could we find another insert material, with higher thermal conductivity (> 174 W/mK), still

low mass and manufacturable?


Antti Onnela, CERN

Case Pipe CO2 Insert Glue Total1 0.10 1.54 2.57 1.78 5.402 0.11 0.85 2.57 1.95 4.913 0.10 1.46 2.56 1.68 5.214 0.11 0.81 2.55 1.87 4.785 0.09 1.41 2.55 1.64 5.116 0.09 1.39 2.55 1.61 5.06

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“Mechanical Strength of the 2S Module Insert – Cooling Pipe Joints”


Antti Onnela, CERN

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Loads and properties

Mechanical properties of the insert / cooling pipe assembly

Aluminium Stainless steel Copper-nickel Araldite 2020

CTE [1/K] 23.1 10-6∙ 16.5 10∙ -6 16.2∙10-6 8.5∙10-5

Modulus of elasticity [GPa] 70 193 152 N/A

Ultimate strength [MPa] 310(tensile)

600 – 800 (tensile)

380 – 590 (tensile)

~ 15(shear)

Yield strength [MPa] 280 300 at 0.2 % elongation

120 - 550 at 0.5 %

elongationN/A

Elongation at break [%] 12 - 15 35 45 N/A


Antti Onnela, CERN

Carbon-fibre frame:CTE: ~ 0.Stiffness: Very high compared to the thin-walled cooling pipe

CTE difference between carbon-fibre frame and cooling pipe leads with ∆T of 60 ⁰C to tension loads on the inserts:~ 100 N with copper-nickel pipe~ 125 N with stainless steel pipe

The tension load could lead to detaching the cooling pipe from the insert, or detaching the insert from the carbon-fibre frame.

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Test assemblies

Test assemblies made with • 10 mm glue joint length

– The final connections are likely to be longer !• Four different test assemblies, 3 samples by

type: Two geometries (images above) Two version of the glue joint

1. Well glued joints2. Glue joints with Teflon coating on the cooling

pipe (as used in the TOB)


Antti Onnela, CERN

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Test results

• Well glued broke in the pipe• As expected, 10 mm glue joint stronger than the 0.1 mm

walled pipe.• Exception in one sample, where the glue joint broke

completely. Not yet understood why.• Teflon coated broke in the glue joint

• As expected and wanted


Antti Onnela, CERN

Well glued With Teflon coated pipes

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Results and conclusions

Expected value

Test results

Average σModulus of elasticity [GPa] 152 142.83 7.70

Ultimate strength [MPa] 495 498.50 13.94Yield strength [MPa] 345 464.39 0.01

Elongation at break [%] 12 - 15 15.76 6.97Maximum force [kN] 0.33 0.33 0.15


Antti Onnela, CERN

Test resultsAverage σ

Ultimate strength [Mpa] 353.28 62.13Maximum force [kN] 0.23 0.04

Well glued samples: Pipe broken Teflon coated samples: Glue joint slipping

Conclusions:• Maximum load carried by the joints (0.33 kN, 0.23 kN) is higher than the load (0.1 – 1.3 kN) from

the CTE differences between the carbon-fibre and the cooling pipe and ∆T of 60 ⁰C.• These need to be recalculated and tested when changing the pipe and insert dimensions (here old

TOB cooling pipes and 10 mm glue joints were used).

• Will try understand why one well glued joint broke, whereas the pipe should have broken.

• Teflon in the tested glue joints acted, as wanted, as a fuse.• In these samples 10 mm glue joint length. With longer glue joints, the Teflon connected joint will

be stronger, the fuse effect wrt to pipe strength will not be very big• Need to see if we want to pursue with this “sliding cooling contact” concept further or not.• If yes, the choice of adhesive and “Teflon” needs to be carefully selected and tested.

“Heat Transfer Capacity of the 2S Module Support Insert”

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