1. WP4 Liverpool 21 June 2012 Graham Beck 1 Summary/Update of Steady State FEA: Perfect Plank and Plank with a small fault. New: Simulation of Transient behaviour (after CO2 flow turned on). Potentially more sensitive to faults. Thermal Load: Assume from AMBIENT. Potentially the way to do QA? - allows comparison (in “perfect” case) with Tim’s IR measurements - which turn out to be v.useful! Assume 20C, Convection + Radiation combined htc ~ 10W/m 2 K. Assumed Fault: 30mm glue missing between pipe and upper foam - Minimal: affect on thermal runaway <0.5C coolant headroom. (conduction between Upper and Lower foam now suppressed in FEA) Plank Thermal QA (continued) 30mm

2. WP4 Liverpool 21 June 2012 Graham Beck 2 FEA Model Quick & Dirty: Stave130 Module FEA with sensors+hybrids stripped away. Fast and informative … but not particularly accurate ! Only a crude correspondence to measured planklet: 2mm id Ti pipe. Cable Bus top and bottom !! restricted to 98mm: boundary conditions WRONG: NO Heat Flow across ±Z. Material Specific Heats assigned (used in transient case) - but Facing Glue Cv omitted. Same htc top & bottom (clearly wrong) +20C, 10 W/m 2 K

3. WP4 Liverpool 21 June 2012 Graham Beck 3 STEADY STATE, PERFECT plank: comparison with Tim’s IR plot. After a couple of iterations to tie down CO2 temperature (approx. -38.5C) <= This T assumed in following FEA. ABAQUS FEA Tim’s IR (Stavelet3) & Simulation -32 ° C -25°C - °C Scale: Abaqus  T looks about 14% low. Nominal Load over module surface area is ~ 6.5W. Similar to ABC130 hybrid 5-6W (a useful coincidence!). => Some confidence in FEA …

4. WP4 Liverpool 21 June 2012 Graham Beck 4 STEADY STATE – with GLUE FAULT: Max surface T is -26C Plotted bands: -32C=> -36C 0.2C intervals (~ camera resolution) Height of bump is 0.7C (top surface. Also 0.4C bump on bottom surface) Would this show up in practice? - depends on “noise”: bus surface flatness, uniformity, convective fluctuations etc.

5. WP4 Liverpool 21 June 2012 Graham Beck 5 Tim, re Thermal Shock: “What is the typical dT/dt seen during Stavelet Testing with CO2?” Transient QA? Stavelet 3: IR temperature history of two points on the surface, above the pipes, after turning on CO2 (later turning off / back on again) At SP02 (above inlet pipe) T falls ~ 7C/s after turning on CO2… CO2 flows around U-bend, and reaches SP01 after ~43s => speed ~ 12mm/s. -meanwhile, outlet (SP01) is cooled, slowly, by conduction across the plank. (Interesting? ~simultaneous warming when flow stopped). Try to reproduce this in FEA - then assess potential for fault finding...

6. WP4 Liverpool 21 June 2012 Graham Beck 6 Transient FEA… Ideally wanted to model a cylinder of (cold) CO2 and move it smoothly into the pipe, with appropriate contact thermal resistance ….. Not possible in Abaqus? (not sexy enough??). Sledgehammer approach: -Divide pipe surface (crudely!) into 8 x 12.25mm lengths along Z -Transient FEA 1s increments: -Change film conditions for successive sections ( ≡ 12.25mm/s) from +20C, 10W/m 2 K => -38.5C, 8000W/m 2 K. -Apply this to inlet pipe. -After 43s, apply (in reverse sense) to outlet pipe -Allow to settle (a further 43s). (“video” of this is Plank130 Trans2… Range is +20C to -40C) Progressive change from Ambient to CO2 => Plot history of surface T above centre of each pipe (as Tim)

7. WP4 Liverpool 21 June 2012 Graham Beck 7

8. 8 FEA (cooling only) cf Tim’s IR: Surface temperature variation mid Z of FEA Qualitatively similar! But FEA differs by: - No slow intial fall (?) - Slower conductive cooling of outlet - Peak rates ~70% higher -Looks like relative speed of CO2 and Conduction are wrong by a factor ×2 in FEA. Good enough to pursue though… IR: Rate [C/s] vs time T vs time FEA:

9. WP4 Liverpool 21 June 2012 Graham Beck 9

10. 10 FEA TRANSIENT – with and without GLUE FAULT (half way along outlet pipe) PERFECT FAULTY Rate [C/s] vs time (“video”: Trans3 Fault… Range is 0C to -40C) T(t) is similar: slightly higher final outlet temp. in faulty case. Peak Rate is same on inlet side (~11C/s), but ~25% lower over fault. Looks promising – but this is cheating (I know where the fault is). Consider a QA algorithm….. T vs time

11. WP4 Liverpool 21 June 2012 Graham Beck 11 A Trivial QA Algorithm: Define lines L1,L2 on the surface above the pipes. Record T on L1, L2 for duration of test (this would be ~ 5 mins for a full stave) For each Z, evaluate dT/dt(t). Plot Peak dT/dt vs Z. Look for anomalies (bumps) The plots are derived in this way from the FEA Temperatures at 2x20 nodes along the bus tape. [Fluctuations due to jerky FEA! Ignore Z extremes – wrong BCs!] => Inlet behaviour is fairly level... => Outlet shows expected bump due to fault. So there is an appreciable signal !!...BUT...... there will be background conduction from ± Z...and what is the noise like in practice??? Many Questions: Best answered by experiment!

12. WP4 Liverpool 21 June 2012 Graham Beck 12 Measurement of IR Emissivity of Bus Tape Emissivity seems high – as hoped. NASA-TP-2005-212792 (re cooling spacecraft) give, for 1mil Kapton on Alumium:  = 0.67. Panic!! But realise this is integrated over all wavelengths! Our IR devices measure in 8-13  m wavelength window, somewhat < Kapton thickness (25  m). But note  is a bit lower for the tape cf the coverlayer (no aluminium). So maybe this is ok ! coverlayer bus tape