26 May 2010 Hans Postema - CERN

Status and plan for the development and construction

of CO2 Cooling System for Pixel Upgrade

1

Why CO2?

• Radiation hard• Not electrically conductive, non corrosive• Not flammable, not toxic• Has excellent thermodynamic properties for micro-

channels. • Low dT/dP• Low mass • Low liquid/vapour density ratio• Low viscosity• High latent heat• High heat transfer coefficient• Environmental friendly

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Pressure advantage

• Intuitively, higher pressures seem a disadvantage but:

• Gas flow at higher pressures needs smaller pipe diameters

• Pressure drops due to flow become less significant, allowing smaller pipes

• Small pipes can easily support the required pressures

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Selection

• Many activities in different places

• Good overview requires several hours

• Global overviews risk to be repeating themselves through the year

• This presentation is a selection of some important achievements over the last few months

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FPIX tube (February)

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FPIX in fridge

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Layout of the test section

Length of the tube: 1mInner diameter: 1.4mmWall thickness: 100µm

13 temperature sensors glued on the tubeCopper blocks for power supply

Improved insulation

• Environment influences obviously the readings of the sensors

• Better insulation of the tube needed

• Freezer must be at the same temperature as the cooling fluid

Kapton tapeTube Armaflex

Improvements

Better results through insulating the tube and keeping the temperatureinside the freezer at the temperature of the liquid

Temperature drop vs. tube length at 0°C

Sensor 1 and 13 are before or after the heated test section

Temperature drop vs. tube length at -15°C

Sensor 1 and 13 are before or after the heated test section

Comparison to correlations

Temp. Thome Friedel Test 1 Test 2

Temperature drop9°C

0.34 °C 0.27 °C 0.05 °C 0.18 °C

Pressure drop 0.35 bar 0.32 bar 0.34 bar 0.36 bar

Temperature drop0°C

0.37 °C 0.37 °C 0.49 °C 0.52 °C

Pressure drop 0.43 bar 0.38 bar 0.50 bar 0.59 bar

Temperature drop-15°C

0.39 °C 0.49 °C 0.82 °C 0.89 °C

Pressure drop 0.61 bar 0.68 bar 1.25 bar 1.37 bar

Temperature drop-30°C

0.47 °C 0.67 °C 1.41 °C 1.46 °C

Pressure drop 1.05 bar 1.33 bar 3.63 bar 3.93 bar

Comparison @ Tsat=9°

Comparison @ Tsat=0°

Comparison @ Tsat=-15°

Comparison @ Tsat=-30°

Conclusions of tests

• Software of some correlations now fully debugged an operational

• Interesting differences between calculations and measurements remain

• FPIX tube can reliably cool the requested heat load of 124 W

• dT over tube length < 3 degrees C

• dT due to HTC < 3 degrees C

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18 May 2010

• Reached an important milestone

• First time that the Full Scale cooling plant test setup was running

• No problem in priming the pump

• Pump runs very quiet and smooth, no vibrations

• The result of a year of work by a dozen people

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Cooling plant

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Including dummy load

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Chiller part

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View with control rack

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Control interface

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Next steps

• Commissioning of the plant at ambient temperature

• Test run of Atlas IBL cooling loop

• Installation of accumulator, required for low temperature operation

• Commissioning of the plant at low temperature

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Strategy (1)

• CO2 cooling plants cannot be bought off the shelf

• Relevant experience is not available in industry

• Current activities are generating the necessary experience “in house”

• Future CO2 cooling plants shall be designed and constructed “in house”

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Strategy (2)

• Cooling plant shall be constructed early, leaving 1 year for commissioning on the surface and 1 year for installation in UX

• To avoid schedule constraints, one cooling plant foreseen for detector commissioning in TIF, and one for installation in the CMS cavern

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Qualification

• Engineering and design shall follow the principles applied in aero-space or safety critical industrial applications

• Excellent workmanship shall have a priority over low-cost

• Extended “burn in” period necessary, comparable with satellites (1 year)

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Safety

• High pressure is a safety concern when combined with larger volumes (stored energy)

• Pipe-work and components are in PED class 1 (Pressure Equipment Directive) DN<32 requiring “Good Practice”

• Storage tanks or Accumulators are in class 4 requiring certification

• Accumulator for the full scale test setup will be produced with a CE certificate, by NIKHEF

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Schedule

• 2010 – Testing of Full Scale setup

• 2011-2012 – Engineering and design of detector parts, pipe-work, fittings and final plant

• 2013 – Construction of cooling plants

• 2014 – Burn in of cooling plants in TIF

• 2015 – Installation cooling plant in UX

• 2016 – Installation of detector

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Participating groups

• CERN – Atlas• CERN – CMS• CERN – PH-DT• CERN – EN-CV• CERN – Cryolab• EPFL Lausanne• Fermilab• IPN Lyon

• NIKHEF Atlas LHCb• PSI• RWTH Aachen• SLAC Atlas• University Esslingen• University Karlsruhe

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