1 2S Module meeting, 24 September 2012 S tudies on module support inserts Refers to work by Riikka Häsä, Helsinki Institute of Physics, summer student at CERN S module meeting, 24 September 2012, indico: 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

2 “Heat Transfer Capacity of the 2S Module Support Insert” 2S module meeting, 24 September 2012, indico: Antti Onnela, CERN

3 Module support insert thermal analysis 2S module meeting, 24 September 2012, indico: Antti Onnela, CERN Insert material properties used AluminiumThermal conductivity, k174 W/mK EpoxyThermal conductivity, k0.2 W/mK Stainless steelThermal conductivity, k15.1 W/mK CO 2 Heat transfer coefficient, h … W/m 2 K Module power estimates Power of a complete module [W] 2x8 CBCs 2 concen- trators L-P GBTGBTIAGBLD Power converter TOTAL Power per support insert next to service board [W] Power per support insert opposite to service board [W] 0.3

4 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 2S module meeting, 24 September 2012, indico: Antti Onnela, CERN

5 Module support insert thermal analysis Cases analysed: 1.25 mm long insert, h = W/m 2 K 2.25 mm long insert, h = W/m 2 K 3.30 mm long insert, h = W/m 2 K 4.30 mm long insert, h = W/m 2 K 5.35 mm long insert, h = W/m 2 K 6.40 mm long insert, h = W/m 2 K 2S module meeting, 24 September 2012, indico: Antti Onnela, CERN CasePipeCO2InsertGlueTotal

6 Module support insert thermal analysis Cases analysed: 1.25 mm long insert, h = W/m 2 K 2.25 mm long insert, h = W/m 2 K 3.30 mm long insert, h = W/m 2 K 4.30 mm long insert, h = W/m 2 K 5.35 mm long insert, h = W/m 2 K 6.40 mm long insert, h = W/m 2 K 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? 2S module meeting, 24 September 2012, indico: Antti Onnela, CERN CasePipeCO2InsertGlueTotal

7 “Mechanical Strength of the 2S Module Insert – Cooling Pipe Joints” 2S module meeting, 24 September 2012, indico: Antti Onnela, CERN

8 Loads and properties Mechanical properties of the insert / cooling pipe assembly AluminiumStainless steelCopper-nickelAraldite 2020 CTE [1/K]23.1∙ ∙ ∙ ∙ Modulus of elasticity [GPa] N/A Ultimate strength [MPa] 310 (tensile) 600 – 800 (tensile) 380 – 590 (tensile) ~ 15 (shear) Yield strength [MPa] at 0.2 % elongation at 0.5 % elongation N/A Elongation at break [%] N/A 2S module meeting, 24 September 2012, indico: 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.

9 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 joints 2.Glue joints with Teflon coating on the cooling pipe (as used in the TOB) 2S module meeting, 24 September 2012, indico: Antti Onnela, CERN

10 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 2S module meeting, 24 September 2012, indico: Antti Onnela, CERN Well glued With Teflon coated pipes

11 Results and conclusions Expected value Test results Averageσ Modulus of elasticity [GPa] Ultimate strength [MPa] Yield strength [MPa] Elongation at break [%] Maximum force [kN] S module meeting, 24 September 2012, indico: Antti Onnela, CERN Test results Averageσ Ultimate strength [Mpa] Maximum force [kN] 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.