Engineering Forum experiences from cooling systems for LHC

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Engineering Forum: experiences from cooling systems for LHC detectors CO 2 cooling experiences in

Engineering Forum: experiences from cooling systems for LHC detectors CO 2 cooling experiences in the LHCb Velo Thermal Control System Bart Verlaat National Institute for Subatomic Physics (NIKHEF) Amsterdam, The Netherlands CERN, 30 October 2008 1

Table of Contents • CO 2 cooling and the 2 PACL method • LHCb-VELO

Table of Contents • CO 2 cooling and the 2 PACL method • LHCb-VELO Thermal Control System (VTCS). • Commisioning results of the VTCS. • Conclusions. 2

Why Evaporative CO 2 Cooling? The lightest way of cooling is: Evaporate at high

Why Evaporative CO 2 Cooling? The lightest way of cooling is: Evaporate at high pressure! Why? Vapor expansion is limited under high pressure d. P/P is small Volume stays low Pipe diameter stays low Mass stays low Low mass flow High latent heat Carbon Dioxide 3

Saturation curves in the PT Diagram for CO 2, C 2 F 6 &

Saturation curves in the PT Diagram for CO 2, C 2 F 6 & C 3 F 8 (3 used or considered refrigerants at CERN) Pressure (Bar) 75 CO 2 50 C 2 F 6 25 C 3 F 8 0 -60 -40 -20 0 20 40 Temperature (°C) 4

Property comparison Better Refrigerant “R” numbers: R 744=CO 2 R 218=C 3 F 8

Property comparison Better Refrigerant “R” numbers: R 744=CO 2 R 218=C 3 F 8 R 116=C 2 F 6 Saturation Temperature (ºC ) Liquid Viscosity Saturation Temperature (ºC ) d. T/d. P (ºC/bar) Better Surface Tension (N/m) Better Liquid Viscosity (Pa*s) Better ρvapour/ ρliquid Density Ratio (ρvapour/ ρliquid) Better Latent heat of evaporation (k. J/kg) Latent Heat of Evaporation 5 Saturation Temperature (ºC )

2 evaporative cooling principles used in LHC detectors Atlas Inner Detector: Vapor compression system

2 evaporative cooling principles used in LHC detectors Atlas Inner Detector: Vapor compression system Liquid BP. Regulator Warm transfer Cooling plant Heater Compressor Pressure Fluid: C 3 F 8 Vapor 2 -phase Enthalpy Detector LHCb-VELO: 2 PACL pumped liquid system Fluid: CO 2 Liquid Vapor Pressure Compressor Pump Chiller Liquid circulation 2 -phase Cold transfer Enthalpy Cooling plant Detector 6

Condenser Long distance P 4 -5 6 4 2 1 Pump Heat in 5

Condenser Long distance P 4 -5 6 4 2 1 Pump Heat in 5 3 evaporator Heat exchanger 2 PACL principle ideal for detector cooling: - Liquid overflow => no mass flow control - Low vapor quality => good heat transfer - No local evaporator control, evaporator is passive in detector - Very stable evaporator temperature control at a distance (P 4 -5 = P 7) Pressure 2 -Phase Accumulator Heat out P 7 Heat in Heat out The 2 -Phase Accumulator Controlled Loop (2 PACL) P 7 Restrictor Vapor Liquid 2 3 2 -phase 4 1 6 5 7 Enthalpy

LHCb Detector Overview Goals of LHCb: Studying the decay of B-mesons to find evidence

LHCb Detector Overview Goals of LHCb: Studying the decay of B-mesons to find evidence of CP-violation LHCb Cross section (Why is there more matter around than antimatter? ) Vertex Locator tron Elec Muon Proton beam Hadron 20 meter Proton beam 8

The LHCb-VELO Detector (VErtex Locator) Detectors and electronics • Temperature detectors: -7ºC • Heat

The LHCb-VELO Detector (VErtex Locator) Detectors and electronics • Temperature detectors: -7ºC • Heat generation: max 1600 W ons to ev pa VELO Thermal Control System CO 2 evaporator section an cap d r illa etu rie rn s ho se 23 el rall ra apo ati r st 9

The Velo Detector Detection Silicon Heat producing electronics Particle tracks in the VELO from

The Velo Detector Detection Silicon Heat producing electronics Particle tracks in the VELO from an LHC injection test (22 august ’ 08) CO 2 evaporator (Stainless steel tube casted in aluminum) 10

VELO Cooling Challenges • VELO electronics must be cooled in vacuum. – Good conductive

VELO Cooling Challenges • VELO electronics must be cooled in vacuum. – Good conductive connection – Absolute leakfree • Maximum power of the electronics: 1. 6 k. W • Silicon sensors must stay below -7°C at all times (on or off). • Adjustable temperature for commisioning. – -5°C to -30°C in vacuum (Nominal -25°C) – +10°C to-10°C under Neon vented condition • Maintenance free in (inaccessable) detector area 11

VTCS Evaporator liquid inlet (¼”x 0. 035”) 2 -phase outlet (⅜”x 0. 035”) Aluminium

VTCS Evaporator liquid inlet (¼”x 0. 035”) 2 -phase outlet (⅜”x 0. 035”) Aluminium casted evaporator block details PT 100 cables vacuum feed through capillaries and return hose Inlet capillaries Finner=0. 5 mm (L~2 m) 23 parallel evaporator stations Finner=1 mm (L~1. 5 m) 12

LHCb-VTCS Overview (VELO Thermal Control System) Accessible and a friendly environment 2 CO 2

LHCb-VTCS Overview (VELO Thermal Control System) Accessible and a friendly environment 2 CO 2 2 PACL’s: 1 for each detector half 4 m thick concrete shielding wall 2. 6 m PLC 2 R 507 A Chillers: 1 water cooled 1 air cooled Inaccessible and a hostile environment 4 m 2 Evaporators 800 Watt max per detector half 2 Concentric transfer lines 55 m VELO 13

Concentric transfer line Transfer line is a 55 m long concentric 2 -fase liquid-vapor

Concentric transfer line Transfer line is a 55 m long concentric 2 -fase liquid-vapor line Functions: • Transferring liquid to evaporators • Regulate liquid temperature • Pick up environmental heat in return line for unloaded evaporator cooling • Provide low-pressure drop return flow for distant evaporator pressure control VTCS total upward column: 4 m+2. 6 m = 6. 6 m ΔT ≈ 0. 7°C → ≈ 0. 1°C/m (C 3 F 8 ≈ 2. 3°C/m) 2 -phase return line Protective cover Ø 1 4 m m Ø 16 mm Ø 6 25 mm Armaflex NH Isolation Ø 4 m m Ø 66 mm Sub-cooled liquid feed line 4 m 2. 6 m Terminals as built 14

VTCS Accumulator Control Set point Temperature Pressure Tset Temperature Cooling spiral for pressure decrease

VTCS Accumulator Control Set point Temperature Pressure Tset Temperature Cooling spiral for pressure decrease (Condensation) Accumulator properties: • • • Volume: 14. 2 liter (Loop 9 Liter) Heater capacity: 1 k. W Cooler capacity: 1 k. W System charge: 12 kg (@23. 2 liter) System design pressure: 135 bar Pset + _ ΔPfault PID + _ Evaporator Pressure Heating Cooling Paccumulator ++ Pressure drop Thermo siphon heater for pressure increase (Evaporation) 15

VTCS Schematics 2 x CO 2 2 PACL’s connected to 2 R 507 A

VTCS Schematics 2 x CO 2 2 PACL’s connected to 2 R 507 A chillers (Redundancy) Lots of sensors and valves 16

VTCS construction • CO 2 2 PACL’s – Stainless steel piping with: • (Orbital)

VTCS construction • CO 2 2 PACL’s – Stainless steel piping with: • (Orbital) Welding • Vacuum Brazing • Swagelok Cajon VCR fittings and line components – Lewa liquid CO 2 pump (100 bar) – In house designed accumulator (130 bar) – Reinforced SWEP condenser (130 bar) • Now commercial available at SWEP. • • – 55 meter concentric transfer line – Aluminium casted cooling blocks – Test pressure 170 bar Chillers designed in house with standard commercial chiller components. – – Copper piping with hard solder joints Danfoss line components Bitzer compressors SWEP heat exchangers Siemens S 7 -400 series Programmable Logic Controller (PLC) 17

LHCb-VTCS Cooling Plant Freon chiller systems Accumulators Valves Pumps CO 2 2 PACL systems

LHCb-VTCS Cooling Plant Freon chiller systems Accumulators Valves Pumps CO 2 2 PACL systems Condensers 18

VTCS Units Installed @ CERN Freon Unit CO 2 Unit July- August 2007 19

VTCS Units Installed @ CERN Freon Unit CO 2 Unit July- August 2007 19

VTCS 2 PACL Operation From start-up to cold operation (1) + 2 2 Pump

VTCS 2 PACL Operation From start-up to cold operation (1) + 2 2 Pump head pressure (Bar) 74 -Accumulator liquid level (vol %) 47 - Accumulator pressure (Bar) 54– Evaporator temperature (°C) 11 Pumped liquid temperature (°C) 7 Accumulator Control: 4+ = Heating - = Cooling _ -7 7 4 7 +7 2 20 1

Pressure VTCS 2 PACL Operation From start-up to cold operation (2) B C Accumulator

Pressure VTCS 2 PACL Operation From start-up to cold operation (2) B C Accumulator Cooling = Pressure decrease 5 A 20 °C 2 Path of 54 D 5 1 Set-point range -20 °C 4 -40 °C Enthalpy D A B C 2 5 1 4 2 - Pump head pressure (Bar) 45 - Accumulator pressure (Bar) 54 – Evaporator temperature (°C) 11– Pumped liquid 21 temperature (°C)

March ’ 08: Commisioning of the VTCS Detector under vacuum and unpowered 22

March ’ 08: Commisioning of the VTCS Detector under vacuum and unpowered 22

24 June ’ 08: After a succesful commisioning of the detector at -25°C, the

24 June ’ 08: After a succesful commisioning of the detector at -25°C, the setpoint is increased to -5°C. Temperature (°C), Power (Watt), Level (vol %) And has been running since then smoothly! (3 sept 08) 80 Accu Heating/Cooling 60 Accu level 40 Detector half heat load (x 10) Module Heat load 20 0 -7°C Silicon temperature SP=-5°C -20 SP=-25°C -40 0 Evaporator temperature 0: 30 1: 00 Time (Hour) 1: 30 2: 00 23

VTCS performance overview for a setpoint of -5°C (Detector switched on, fully powered) Cooling

VTCS performance overview for a setpoint of -5°C (Detector switched on, fully powered) Cooling block temperature = -2. 8°C CO 2 liquid temp= -42°C Evaporator liquid inlet temp = -4. 40°C 1 hour Fluctuations from the untuned chiller CO 2 liquid d. T=4. 5°C Detector offset from accu control: 0. 7°C d. P=0. 6 bar = 6. 2 m static heigth Evaporator Pressure 31. 15 bar = -4. 18°C Cooling block d. T=0. 04°C CO 2 heat transfer d. T=1. 4°C Evaporator vapor outlet temp = -4. 44°C Accumulator Pressure 30. 54 bar = -4. 90°C 24

Summary • The VTCS has successfully passed the 1 st commissioning phase and was

Summary • The VTCS has successfully passed the 1 st commissioning phase and was ready to be used in the experiment in July 2008 • Operational temperature range is between -5°C and -30°C set point for the water cooled chiller • It has run for 3½months continuously with only minor problems • It behaves very stable with the chiller still to be tuned (evaporator stability less than 0. 05°C) • The silicon temperature is below the required -7°C @ -25°C set point temperature. (This is consistent with the prediction) 25

What did we learn: • 2 PACL dynamics work better with the accumulator connection

What did we learn: • 2 PACL dynamics work better with the accumulator connection at inlet of condenser (instead of outlet as it is now) – No saturated liquid feed from accu to pump. – Free pre-cooling at cold start-up due to thermal capacity of condensers. • Concentric transfer tube heat exchanger works beyond expectations as the so-called “Duck-footcooling 1” pinciple is boosting the operational temperature range. • The current system is not always initiating boiling at higher operational temperatures (>-10°C), resulting in temporary reduced heat-exchange. 1 The way a duck can have cold feet without loosing body heat, by exchanging heat between the in- and outlet bloodstream. 26

The “Cool” future • The VTCS is not yet finnished, some things have to

The “Cool” future • The VTCS is not yet finnished, some things have to be done: • Construction of a mini desktop 2 PACL CO 2 circulator for general purpose laboratory use. • Participation in future CO 2 cooling systems • 2 PACL upgrade: – – Implementing automatic back-up procedure. Changing the accumulator connection. Tunning the chiller. Analyse data for publication. – Atlas IBL, Goat, Next-64, RELAXed – Replace HFC chiller by CO 2 chiller • No integration of chiller and 2 PACL! – 2 PACL is much more stable (<0. 05’C) – 2 PACL has liquid overfeed and needs no boil-off heaters – CO 2 compressor needs oil as lubricant • CO 2 chiller has extended lower temperature range (CO 2 ~-50°C , HFC~40°C ) 27

Back-up Slides 28

Back-up Slides 28

Property Comparison (1) R 744 (CO 2) R 116 (C 2 F 6) R

Property Comparison (1) R 744 (CO 2) R 116 (C 2 F 6) R 218 (C 3 F 8) Source Refprop NIST R 744 (CO 2) R 218 (C 3 F 8) R 116 (C 2 F 6) Critical Point 31ºC @ 73. 8 bar 71. 9ºC @ 26. 4 bar 19. 9ºC @ 30. 5 bar Triple point -56. 6ºC -147. 7ºC -100ºC Boiling temperature @ 1 bar -78. 4ºC Sublimation ! -36. 8ºC -78. 1ºC 29

Q = 680 Watt Tube = 4 meter Example of and Atlas upgrade stave

Q = 680 Watt Tube = 4 meter Example of and Atlas upgrade stave (1) 2 x 20 wafers à 17 Watt Cooling Calculations based on -35°C and 75% vapor quality at exit ΔT=-2°C 3 F 8 Pressure Drop Mass flow @ -35ºC Φ CO 2= 2. 9 g/s Φ C 3 F 8= 8. 7 g/s Φ C 2 F 6= 9. 6 g/s C 3 F 8 C 2 F 6 CO 2 1 Atlas stave : 2 meter length Generate s CO CF 2 2 =2. 7 m 6 =4. 3 mm m Temperature Drop CF 3 8 =7. 7 m m 30

D 2. 7 mm x L 25 mm = 80167 W/m 2 CO 2

D 2. 7 mm x L 25 mm = 80167 W/m 2 CO 2 Example of and Atlas upgrade stave (2) Heat exchange length 25 mm 75 mm D 4. 3 mm x L 25 mm = 50337 W/m 2 D 2. 7 mm x L 75 mm = 26722 W/m 2 C 2 F 6 C 3 F 8 D 4. 3 mm x L 75 mm = 16779 W/m 2 D 7. 7 mm x L 25 mm = 28110 W/m 2 D 7. 7 mm x L 75 mm = 9370 W/m 2 25 mm H X length C 3 F • 87. 7 Mass flux @ -35ºC Φ’ CO 2= 506 kg/m 2 s Φ’ C 3 F 8= 661 kg/m 2 s Φ’ C 2 F 6= 186 kg/m 2 s Critical Heat Flux (Bowring/Ahmad): CHF(CO 2) = 313 k. W/m 2, x=1. 1 75 mm H X length CO 2 C 2 F 6 31