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First look at the cooling requirements for the UT detector

LHCb CO2 cooling kick-off meeting 28 May 2014 CERN. First look at the cooling requirements for the UT detector. Simone Coelli I.N.F.N . MILANO. Summary. Overview Cooling power requirements for the upgrade of the UT detector UT Detector cooling open issues

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First look at the cooling requirements for the UT detector

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  1. LHCb CO2 cooling kick-off meeting • 28 May 2014 • CERN First look at the cooling requirements for the UT detector Simone Coelli I.N.F.N. MILANO

  2. Summary • Overview • Coolingpowerrequirements for the upgrade of the UT detector • UT Detector cooling open issues • Open points and questions

  3. LHCb UT detector upgrade • OVERVIEW • STAVE ELEMENTS • 16 +16 +18 +18 = 68 • TOTAL NUMBER OF STAVES • 3 STAVE FLAVOURS: • 8 + 8 + 52 = 68 • Four Planes of Silicon Strip Sensors • with ASICs readout • Support with integrated cooling

  4. THERMAL REQUIREMENTS • POWER • ASICs READ-OUT Power electrical dissipation expected = 3200 W • + SELF-HEATING + POWER FLEX DISSIPATION => • 4000 W OF DISSIPATED THERMAL LOAD TO BE REMOVED • Considering a margin to take into account the box and the transfer lines insulation.. • => 4 to 5 kW cooling system power • CO2 INLET TEMPERATURE • SENSOR OPERATING TEMPERATURE ALWAYS UNDER - 5 °C • ASICs OPERATING TEMPERATURE NOT EXCEEDING 40 °C • Studies have been done on the thermal transfer, work is ongoing to limit the thermo-mechanical stress over the silicon sensor (100mm*100mm) • Inlet CO2 liquid supply T from - 10 °C to - 35 °C • With the possibility to regulate the inlet fluid temperature

  5. OTHER REQUIREMENTS The detector isopenablemade in twohalves=> the coolingconnectionsshould be attached on the twosides (symmetric flow division)=> having the possibility to open the semi-detector assembly (about800 mm) possiblyrelying on the transfer line flexibility Actual UT CLOSE POSITION (DATA-TAKING) OPEN POSITION (MAINTENANCE)

  6. UT Detector • coolingopen issues

  7. INTERNAL STAVE GEOMETRY • Halflenghtstaverepresentedhere • SNAKE PIPE DESIGN • BASELINE (BEST THERMAL PERFORMANCE) • Stave with a bended pipe embedded in the stavesupportpassingunderneath the ASICs • 2 STRAIGHT PIPES DESIGN • OPTIONAL CONFIGURATION • Stave with twostraightpipesrunningverticallyparallelto the longitudinalstaveaxis

  8. Sensor attachment • Has an effect • on the stavethermalprofile • on the thermo-mechanicalbehaviour (to guaranteealloweddeformation and stress) example • Severalsensormechanicsoptions un study

  9. CO2 Boilingflow direction (upward/downward) • To be decidedwhatis the best option • Can be simulatedusing the CO2 code CoBRA? • Should be testedusing a full scale prototype, • UTbXhalf-planerepresentation, for the snake pipe option

  10. HALF PLANE • FLOW DISTRIBUTION • IN THIS SITUATION USING EVAPORATIVE • COOLING: • THERMO-HYDRAULIC INSTABILITIES CAN ARISE • GEOMETRY OF THE SERPENTINE FOR THE CENTRAL STAVE • IS DIFFERENT: • 4 MORE BENDS • > TOTAL LENGHT • COOLING DISTRIBUTION SYSTEM DESIGN: • DEDICATED COOLANT PRESSURE DROP AT EACH STAVE INLET • INLET FLOW TROUGH CAPILLARIES WITH A DEDICATED CALIBRATION • SYSTEM TEST FOR THIS SUBASSEMBLY TO VERIFY THE DESIGN APPROXIMATE STAVE POWER DISTRIBUTION THE STAVES HAVE DIFFERENT THERMAL LOADS Total coolingpower~ 500 W

  11. manifoldconceptual sketch Supposingsnakepipes and an upward flow: • Exhaustmanifold : • Stainlesssteel • 8/9 welded pipe fittingconnections • Coolantinletdistribution: • Capillaries for liquid flow distribution • L1 • L2 • L3 • Optimizedlengths L1 L2 L3

  12. manifoldconceptual sketch Supposingsnakepipes and an upward flow: Exhaustoutlet line flow re-balancing system using capillaries connection to a common manifold? => half detector: 34 CO2 supply lines 3 inlet DP flavours: 4 * L1 + 4 * L2+ 26 * L3 CO2 supply line

  13. THERMO-HYDRAULIC CHARACTERIZATION OF THE SNAKE PIPE • A POSSIBLE HALF PLANE FLOW DISTRIBUTION TEST SET-UP THE MOST UMBALANCED SITUATION TO BE TESTED TO DEMONSTRATE STABILITY OF THE SYSTEM • ONLY CENTRAL STAVE POWER ON • TRACI COOLING SYSTEM COULD BE USED (POWER 100 W)

  14. Detector geometryone of the two half-detector unit 225 mm 45 mm 45 mm ~ 1500 mm

  15. OPEN POINTS & QUESTIONS • UT Detector responsibility (definition of points) • Transfer line is part of the coolingplant? • Failureanalysis: proposals • VELO/UT coolingplants: inter-connection or separatedsystems? • How to proceed for the design • Coolingsystemsimulation for design and optimization,CoBRA • Max pressure design for the pipingsystem(MDP=10 Mpastartingassumption)

  16. Back-up slides

  17. Prototypetesting • Single stave => blownsystem • Half-plane =>TRACI system • Full scale ..?

  18. Electronicspowerdissipation => Thermal loads ASICsdissipatedthermalpower: 0,768 mW / ASIC Thishalfstavehas on it a total44 ASICsincludingbothupstream & downstream faces => 44 * 0,768 = 33,8 W total • «centralstaves» • Number = 8 • Cut-out for the the beampipe • with 8 ASICsread-out • Higherthermalload SENSORS self-heating thermalpower: A1.T8 13mW A1.T717mW Data-PowerFlexbus dissipatedthermalpower: + 2 W upstream face + 2 W downstream face A1.T623mW A1.T5 34mW A1.T4 58mW A1.T3 135mW A1.T2 No Griddistribution* =total 171mW downstream face • upstream face A1.T1 No Griddistribution* = total 261 mW

  19. Flow regulation valve

  20. UT DETECTOR THERMAL MANAGEMENT • TEMPERATURE REQUIREMENTS REMINDER • SENSOR OPERATING TEMPERATURE ALWAYS UNDER -5 °C • ASICsOPERATING TEMPERATURE NOT EXCEEDING 40 °C • SOME CONSIDERATIONS ON THE EXTIMATED TERMAL GRADIENTS • COMING FROM THERMAL FINITE ELEMENT ANALYSIS • ANALYSIS : STEADY-STATE FOR NOMINAL OPERATING CONDITION • BASED ON THE CENTRAL STAVE GEOMETRY MODEL – IT IS THE MAX POWERED STAVE • EXPLOITING AN IMPROVED DESIGN: USING ALL CARBON FOAM CORE • CALCULATION CLEARLY IS IN IDEAL CODITIONS: PERFECT ADHESION OF GLUE AND THERMAL CONTACTS • CONDUCTIVE MATERIAL PROPERTIES USED ARE A GUESS • SENSITIVITY ANALYSIS HELP TO SEE THE EFFECTS OF INPUT CHANGE ON THE TEMP. SOLUTION • => SAFETY MARGIN SHOULD BE USED IN COOLING DESIGN TO ACCOUNT FOR SIMULATION APPROXIMATION

  21. THE THERMAL F.E. MODEL TAKES IN ACCOUNT ONLY THE THERMAL CONDUCTION • ACROSS THE STAVE MATERIALS • FROM THE THERMAL POWER SOURCES • ASICs DISSIPATION • SENSOR SELF-HEATING • FLEX-BUS DISSIPATION • TO THE COOLING PIPE EMBEDDED INTO THE STAVE AND SERVICING THE TWO STAVE FACES • THE STAVE DESIGN GOAL IS TO MANAGE ALL THE THERMAL LOADS • EXPLOITING THE BEST THERMAL CONDUCTION IN THE STAVE UNTIL THE COOLING PIPE • THERMAL CONVECTION TOWARDS THE FLUID IN THE PIPE • PHASE CHANGE USING THE EVAPORATING COOLANT CO2 • THERE IS AN ADDITIONAL THERMAL CONVECTION WITH THE GAS FLOWING IN THE DETECTOR BOX • TO CONTROL THE BOX ENVIRONMENT • GAS INLET TEMPERATURE SHOULD BE LOWER THAN THE MEAN DETECTOR TEMPERATURE • OTHERWISE THE DETECTOR COOLING SYSTEM WILL HAVE EXTRA WORK => T INLET GUESS: AROUND 0 °C • => MEAN SURFACE TEMPERATURE OF THE STAVES WILL BE CALCULATED FOR AN EVALUATION OF THIS EFFECT • GAS FLOWRATE MUST BE SUITABLY CHOOSEN - DEPENDING ON THE BOX AIR-TIGHTNESS • REQUIREMENT: THE UT BOX DEW-POINT SHOULD BE ADEQUATELY LOW (LESS THAN - 40 °C) • THIS SETS THE MAX HUMIDITY ADMISSIBLE INSIDE THE BOX TO AVOID CONDENSATION ON THE COLD PARTS • THIS DICTATES REQUIREMENTS ON: • THE GAS FLOW PURITY • THE BOX AIR –TIGHTNESS • PROPOSAL: USE NITROGEN FLOW IN A CLOSED LOOP WITH AN EXTERNAL COOLING, MEASURING BOX INTERNAL DEW-POINT • HOT SPOTS (THE ASICs) WOULD DISSIPATE SOME THERMAL POWER TOWARDS THE GAS (MITIGATING TEMPERATURE PEAKS

  22. THERE IS ALSO A UNAVOIDABLE RADIATIVE THERMAL TRANSFER (INFRARED EMISSION) • HELPS HOT SPOTS (THE ASICs) TO DISSIPATE SOME THERMAL POWER TOWARD COLDER SURROUNDINGAND MITIGATING TEMPERATURE PEAKS • DETECTOR THERMAL EXCHANGE TAKES PLACE WITH THE SURFACES INCLOSING THE DETECTOR • DEPENDING MAINLY ON THE TEMPERATURE DIFFERENCE BETWEEN THE EXTERNAL DETECTOR PLANES • AND THE CLOSING BOX SURFACES (THAT COULD BE NEAR TO THE AMBIENT TEMPERATURE) • RADIATION HEAT TRANSFER CALCULATION WOULD NEED A KNOWLEDGE OF MANY PARAMETERS (EXACT GEOMETRY AND TEMP. DISTRIBUTION, VIEW FACTORS AND EMISSIVITY FACTORS) • => CALCULATION WILL BE DONE, • => A SAFETY MARGIN IN THE COOLING DESIGN SHOULD BE TAKEN • FOLLOWS A SUM-UP OF THE RESULTS FOR THE TWO DESIGN : • THE SNAKE PIPE DESIGN • THE TWO STRAIGHT PIPES DESIGN • TEMPERATURES OF: • SENSORS • ASICs

  23. TEMP. CONDUCTIVE GRADIENT RELATIVE TO THE COOLING PIPE INTERNAL SURFACE • SNAKE PIPE DESIGN • INTERNAL STAVE GEOMETRY • SENSOR TEMP. • ASICs TEMP. Max SENSOR T ~ 3 °C Max ASIC T ~ 30°C • STRAIGHT PIPES DESIGN • ASICs TEMP. • INTERNAL STAVE GEOMETRY • SENSOR TEMP. Max ASIC T ~ 40°C Max SENSOR T ~ 11 °C

  24. THERMAL FIGURE OF MERIT IS • BASED ON: • ASIC POWER ~ 0.768 W • ASIC SURFACE ~ 0.52 cm2 • NOTES ON THE RESULTS: • COMMON TO THE TWO DESIGN OPTIONS • SENSORS MAX TEMP. IS AFFECTED BY THE HOTTEST ASIC THAT TRANSMITS HEAT TO THE NEAR SENSOR GIVING RISE TO THE SENSOR HOT-SPOT • ASIC-SENSOR DISTANCE AND FLEXBUS CONDUCTIVITY DRIVING THE EFFECT • ASIC HEAT IS TRANSFERRED ALSO TO THE OPPOSITE FACE SENSOR • SNAKE PIPE DESIGN (COMPLICATION: PIPE BENDING) • ASICs TEMP. ARE RELATIVELY UNIFORM • DUE O THE SNAKE PIPE CONFIGURATION THAT IS DESIGNED TO PASS UNDERNEAT EACH ASIC • ASICs THERMAL FIGURE OF MERIT VARYING FROM 10-20 °C/W/cm2 • WORST ΔT over the sensor AROUND 3 °C • TWO STRAIGHT PIPES DESIGN (COMPLICATION: INSERTS IMPLEMENTATION, DOUBLE PIPE CONNECTIONS) • TPG INSERTS (ARE USED WITH K = 900-900-10 UNDER THE ASICs • ASIC DISTANCE FROM THE PIPE DRIVING THE TEMP. PEAK • ASICs THERMAL FIGURE OF MERIT VARYING FROM 5-30 °C/W/cm2 • WORST ΔT over the sensor AROUND 8 °C • => GENERAL CONCLUSION: THE SNAKE PIPE DESIGN IS THE BEST TO BE PURSUED

  25. STARTING FROM THE THERMAL SIMULATION RESULTS:=> COOLING PIPE TEMPERATURE COULD BE SET TO STATISFY THE REQUIREMENTSSENSOR OPERATING TEMPERATURE ALWAYS UNDER - 5 °C ASICs OPERATING TEMPERATURE NOT EXCEEDING 40 °C • SNAKE PIPE DESIGN => COOLING PIPE T ~ - 8 °C • TWO STRAIGHT PIPES DESIGN => COOLING PIPE T ~ - 16 °C • NOTE THIS IS WITHOUT MARGIN • REQUIRED INLET CO2 FLUID TEMPERATURE COULD THEN BE CALCULATEDTHE EFFECTS RELATED TO THE USE OF A TWO-PHASE COOLANT MUST BE TAKEN INTO ACCOUNT : • PRESSURE DROP IN THE COOLING PIPE IS CAUSING A TEMPERATURE DROP (SATURATE FLUID) • INLET TEMPERATURE IS HIGHER THAN OUTLET (THE FIGURE DEPENDING ON THE PIPE AND ON THEFLUID PARAMETERS ) • INTERNAL HEAT TRANSFER COEFFICIENT (HTC) BETWEEN THE FLUID AND THE PIPE INTERNAL WALL • ADDING A TEMPERATURE GRADIENT TO BE SUPERIMPOSED ON THE LOCAL FLUID TEMP. • • ΔT convective contribution: temperature difference between fluid (bulk) and inner pipe wall • • ΔT conductive contribution: temperature difference across the stave simulated by Finite Element Analysis

  26. TO START THE DESIGN SOME HYPOTHESIS ON THESE THERMAL GRADIENTCAN BE MADEFIGURES BASED ON PREVIOUS EXPERIENCES AND SIMILAR DESIGN ARE AVAILABLEANY SUCH DESIGN NEEDS AN ITERATIVE PROCESS BECAUSE THE COOLING GEOMETRY AND THE THERMO-HYDRAULIC PROCESS ARE INTER-RELATEDDISCLAIMER:THESE CALCULATION NEED TO BE REFINED AND FOLLOWED-UP DURING THE COOLING SYSTEM DESIGN=> REAL SCALE TEST NEED TO BE MADE TO VALIDATE THE CALCULATIONS NOTE GIVEN THE RESPECT OF THE CITED REQUIREMENTS THE UT DETECTOR IS NOT VERY SENSITIVE TO A SMALL CHANGE (FEW DEGREES) IN THE OPERATIVE TEMPERATURE OF A SENSOR LOCATED ON THE INLET OR OUTLET PART OF THE STAVE HALF STAVE CENTRAL GEOMETRY => USING SOME MARGIN THE OPERATIVE INLET CO2 COOLANT TEMPERATURE COULD BE SUPPOSED TO BE FROM - 20 °C TO - 30 °C DEPENDING ON THE DESIGN CHOICE (SNAKE OR STRAIGHT PIPE) • THE FOLLOWING CONSIDERATIONS FOR THE COOLING SYSTEM ARE VALID IN GENERAL FOR BOTH THE DESIGN CASES

  27. THE PURE CO2 SATURATION CURVEHEREAFTER CORRELATES TEMPERATURE AND PRESSURE INSIDE THE EVAPORATION CHANNEL • => 10 TO 20 bar COOLING FLUID • OPER. PRESSURE • - 20 °C TO - 30 °C COOLING FLUID OPER. TEMP.

  28. THE LATENT HEAT OF VAPORIZATION FOR CO2 CAN BE KNOWN FROM THE CO2 PRESSURE-HENTALPY DIAGRAM IN THE RANGE OF INTEREST DELTA H liq.=> vap. = 280 kJ/kg

  29. CONSIDERING FIRST WHAT HAPPENS IN A SINGLE STAVE THE CENTRAL STAVE TOTAL POWER TH THE COOLING PIPE HAS TO EXTRACT IS AROUND 85 W (TAKING INTO ACCOUNT SOME DISSIPATION IN THE FLEXBUS) MASS FLOWRATE • DESIGN OF THE COOLING SYTEM • REQUIRES: • INLET CO2 LIQUID SUBCOOLED • BUT NEAR TO SATURATION • OUTLET VAPOUR FRACTION X OUT= 0.5 TO 0.6 • TO AVOID THE DRY-OUT TAKING X OUT = 50% MASS FLOWERATE NECESSARY CAN THEN BE EXTIMATED: MASS FLOWRATE= 2 * POWER /DELTA HLIQ-VAP = 2* 85 W / 280 kJ/kg = 0.6 g/s LESS FLOWRATE IS TO BE AVOIDED BECAUSE WILL BE GIVING A RISK OF DRYING-OUT MASS FLOWRATE

  30. TO LIMIT THE TEMP.DECREASE => DESIGN CHANNEL PRESSURE DROP HAS TO BE LIMITED ACCEPTING FEW DEGREES MEANS ACCEPTABLE PRESSURE DROP AROUND 1 TO 2 BAR MASS FLOWRATE PRESSURE DROP IS DRIVEN MAINLY BY THE FLOWRATE, GEOMETRY (TOTAL LENGHT AND BENDS), INTERNAL ROUGHNESS, CHANNEL ORIENTATION CHANNEL REAL CONDITION TEST IS NEEDED MEASURING ALL THE HYDRAULIC PARAMETERS FLOWRATE P, T INLET AND OUTLET MASS FLOWRATE

  31. WHAT HAPPENS INSIDE THE CHANNEL • ALONG EVAPORATING CHANNEL: • DECREASING P • DECREASING T TARGET DESIGN FOR THE THERMO-HYDRAULIC CONDITIONS IN THE DETECTOR COOLING CHANNEL AVOID WITH, A SAFETY MARGIN, THE DRY-OUT X OUT < MAX => REQUIRES SUFFICIENT FLOWRATE COURTESY OF BART VERLAAT (NIKHEF - CERN)

  32. DETECTOR COOLING CO2 SYSTEM 2PACL (2-Phase Accumulator ControlledLoop) (Verlaat et al. 2011) UT DETECTOR COOLING CONFIGURATION SHOULD LOOK LIKE THIS: This figure shows a simplified schematic of the circulation system which is used often in particle physics detector cooling. This method controls the system pressure and hence evaporation temperatures by a 2-phase accumulator which is heated or cooled. A heat exchanging concentric transfer line (2-3) brings the liquid in the inlet of the detector cooling pipes into saturation. Like this the evaporation in the detector cooling pipes is always happening at the pressure regulated in the accumulator. Experimental caverns are inaccessible during running of the LHC beam. All the active hardware of a 2PACL can be located in a safe zone (left side of figure 2). This area is always accessible for maintenance. In the experimental cavern preferably only passive piping is present.

  33. DETECTOR COOLING LAY-OUT • supposing to have a modularity with the four UT detector planes divided in: • 1 right half box (composed of 4 half planes) • 1 left half box (composed of 4 half planes) • «CENTRAL» stavepower ~ 90 W • «HALF PLANE»power ~ 500 W • To start thinking on the connectivity of the coolingsystemexploiting CO2 evaporationsystem • Proposal: use for each «halfplane» • 1 lowerinletmanifold, distributingliquid CO2 to the staves • 1 uppermanifold, collectinghexaust CO2 (partiallyevaporated) from the staves «lefthalfplane» «right halfplane» CO2 (~ 50%) Halfplanes are Supposed to move to open like in the actualtracker X := thermodynamictitle Saturatedliquid = 0% Saturatedvapour =100% CO2 (X = 0)

  34. DETECTOR COOLING LAY-OUT • The CO2 coolingplantshould be a 2PACL • system with coolingcapacity: 4000 Watt@-30 °C • Need a specificplant design • Similar to VELO Upgrade • Actual LHCb- VELO • Cooling capacity: 1500 W@-30°C • CONCEPTUAL BRANCHES LAY-OUT

  35. For the study of long length cooling branches with CO2 a program is developed called CoBra Calculator(CO2 BRAnch Calculator) DESIGN OF THE COOLING SYSTEM ANOTHER POINT IS THE PRESSURE DROP OF THE OUTLETLINE • LIFTS UP THE TEMPERATURE PROFILE OF THE COOLING CHANNEL

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