Evaporative CO 2 cooling for thermal control of scientific equipments. Bart Verlaat (Nikhef/CERN)

Transcription

1 Evaporative CO 2 cooling for thermal control of scientific equipments SLAC Advanced Instrumentation Seminars March 28, 2012, 1:30 PM, Kavli 3rd floor Bart Verlaat (Nikhef/CERN) 1

2 CO 2 Cooling Seminar Introduction to 2phase cooling and fluid trade-off CO 2 cooling modeling Introduction to the 2PACL CO 2 circulation method. CO 2 cooling in the AMS-Experiment. CO 2 cooling in the LHCb Velo Detector Ongoing projects. Conclusions 2

3 Temperature ( C) Pressure (Bar) What happens inside a cooling tube? Heating a flow from liquid to gas Liquid Gas Isotherm 2-phase Liquid Superheating Enthalpy (J/kg) Low ΔT Increasing ΔT (Dry-out) Sub cooled liquid Target flow condition 2-phase liquid / vapor Dry-out zone 3 Super heated vapor

4 Cooling efficiently scientific equipment. What do we expect in general from a 2phase flow in scientific equipment? Inside the equipment (Evaporator): Small additional cooling hardware (small diameter tubing) Large heat removal capacity Low temperature gradients Low gradient from tube wall to fluid Low gradient over tube length (Isothermal) Outside the equipment (Circulation system) Stable temperature Control over fluid condition in side evaporator Which fluid is most suitable? 4

5 Temperature Temperature profiles To compare different fluids it must be understood which mechanism contributes to the thermal performance. ΔT(ΔP) (Reduced diameter) ΔT(ΔP) ΔT(HTC) (Reduced diameter) ΔT(HTC) ΔT(ΔP+HTC) (Reduced diameter) ΔT(ΔP+HTC) Tube length For efficient heat transfer: ΔT(ΔP+HTC) as small as possible For isothermal heat transfer: ΔT(ΔP) as small as possible As in general small cooling tubes are preferred, so lets introduce a new property to distinguish the heat transfer relative to the needed volume Overall Volumetric Heat Transfer Conduction (W/m 3 K): Q V tube *ΔT(ΔP+HTC)) Isothermal Volumetric Heat Transfer Conduction (W/m 3 K): Q V tube *ΔT(ΔP)) 5

6 Temperature Heat transfer gradients ( C) Fluid Fluid trade-off regarding temperature gradients, for simplicity: Pressure drop: Friedel correlation Heat transfer gradients: Kandlikar correlation. Trade-off (1) Heat transfer temperature gradients L=1 m, Q=100 W, T=-20 C, VQ=0.5 Total dt(dp+htc) (Thick lines) CO2 (19.7 bar) Ethane (14.2 bar) R11 (10.5 bar) Propane (2.4 bar) R218 (2 bar) Ammonia (1.9 bar) R134a (1.3 bar) CO 2 5 Heat Transfer dt(htc) (Dashed lines) Pressure drop dt(dp) Tube diameter (mm) ΔT(ΔP) (Reduced diameter) ΔT(ΔP) ΔT(HTC) (Reduced diameter) ΔT(HTC) ΔT(ΔP+HTC) (Reduced diameter) ΔT(ΔP+HTC) Tube length

7 Volumetric heat transfer conduction (W/mm 3 K) Volumetric heat transfer conduction (W/mm 3 K) Fluid Trade-off (2) Overall volumetric heat transfer conduction L=1 m, Q=500 W, T=-20 C, VQ=0.5 CO 2 CO2 (19.7 bar) Ethane (14.2 bar) R11 (10.5 bar) Propane (2.4 bar) R218 (2 bar) Ammonia (1.9 bar) R134a (1.3 bar) Isothermal volumetric heat transfer conduction L=1 m, Q=500 W, T=-20 C, VQ=0.5 Isothermal CO 2 CO2 (19.7 bar) Ethane (14.2 bar) R11 (10.5 bar) Propane (2.4 bar) R218 (2 bar) Ammonia (1.9 bar) R134a (1.3 bar) Overall Tube diameter (mm) Tube diameter (mm) Translating the temperature gradients to the volumetric heat transfer conductance Clearly visible: CO 2 is a winner in both overall and isothermal. Another interesting phenomena: The higher the pressure the more efficient. Is this maybe the simple answer to the perfect fluid? 7

8 Is high pressure the answer to an efficient cooling fluid? In fact it is, the higher the pressure: The more the vapor stays compressed The smaller the needed volume But as well: lower gas speeds mean lower pressure drop. Other properties are also important: High latent heat (=less flow) Low viscosity (=low pressure drop) CO 2 is favorable for both properties. And on top of that pressure drop is less significant at high pressures as it doesn t effect the boiling pressure as it would do at low pressure fluids. 8

9 CO 2 a perfect cooling fluid for scientific use As shown, CO 2 is a really good candidate cooling fluid if the following properties are required (In general for scientific and high-tech equipment): Low mass and low volume cooling pipes Isothermal behavior High heat removal capacity The stability in time is a merit of the attached cooling plant, here fore the 2PACL principle was invented for particle detector cooling. However high pressure fluids are less sensitive to pressure changes, so in fact they are as well beneficial for stable temperature systems. 9

10 CO 2 heat transfer and pressure drop modeling Nowadays good prediction models of CO 2 are available. Especially the models of J. Thome from EPFL Lausanne (Switzerland) See SLAC s Advanced Instrumentation Seminar talk by 9 feb 2011 Models are flow pattern based and are reasonably well predicting the flow conditions and the related heat transfer and pressure drop. The Thome models are successfully used to predict the complex thermal behavior of particle detector cooling circuits. A simulation program called CoBra is developed to analyze full detector cooling branches. 10

11 Experimental heat transfer data (measured at SLAC) Interesting research on heat transfer is done at SLAC in a joint effort with Nikhef. M. Oriunno (SLAC) & G. Hemmink (Nikhef) 11

12 CoBra Calculator (CO2 BRAnch Calculator) Q x = Q applied + Q environment +Q exchanged Q x+1 dp x = f(d,q 1,MF,VQ,P,T) or f(cv) P x+1 = P x - dp x H x+1 = H x + dh x dp x+1 P x,h x dh x = Q tot /MF or pump work dh x+1 P x+2,h x+2 dp pump = dp all dh condenser = dh all T x,vq x and properties derived from Refprop Iterative method chopping a long line in small elements (~1mm). Model can read simple configuration files giving simple tube geometry Heat leak and internal heat exchange between elements can be taken into account. CoBra is a very helpful tool for predicting the complex behavior of 2- phase flow. 12

13 Delta T (`C) & Delta P(Bar) Slug Liquid Bubbly CoBra example calculation 2mmID x 5m tube temperature and pressure profile. MF=0.3g/s, Tsp=-30ºC, Q=90, x end = mx1.5mmID tube (4m heated), Mass flow=0.3g/s, Q=90Watt, T=-30ºC Slug Annular dt Tube wall (ºC) dt Fluid (ºC) dp Fluid (Bar) Dry-out Annular Process path Dryout Mist Stratified Wavy Branch length (m) 50 Stratified CoBra is able to analyze complex thermal behavior of CO 2 in long tubes 13

14 Delta T (`C) & Delta P(Bar) Delta T (`C) & Delta P(Bar) Internal heat exchange and ambient heating IBL temperature and pressure profile. MF=0.8g/s, Tsp=-40ºC, Q=101.8, x end = Capillary dt Tube wall (ºC) dt Fluid (ºC) dp Fluid (Bar) dt Pixel Chip (ºC) IBL temperature and pressure profile. MF=0.8g/s, Tsp=-40ºC, Q=101.8, x end = No Boiling dt Tube wall (ºC) dt Fluid (ºC) dp Fluid (Bar) dt Pixel Chip (ºC) 10 8 Stave TFoM: 13ºC*cm 2 /W Pixel maximum temperature: -24.2ºC 10 8 Stave TFoM: 13ºC*cm 2 /W Pixel maximum temperature: -24.4ºC Boiling starts Boiling starts Branch length (m) Branch length (m) Figure 7: CoBra calculation example of the IBL cooling tube. The branch has a 1mm inlet (1-4), a 1.5 mm cooling tube (4-8), a 2mm outlet (8-9) followed by a 3mm outlet (9-12). The dashed temperature profile is the actual sensor temperature taking into account the conductance of the support structure. The graph on the left has no internal heat exchange, the right graph takes internal heat exchange of the in and outlet tube into account. 2 Figures from: DESIGN CONSIDERATIONS OF LONG LENGTH EVAPORATIVE CO2 COOLING LINES Bart Verlaat and Joao Noite, GL-209, 10th IIF/IIR Gustav Lorentzen Conference on Natural Working Fluids, Delft, The Netherlands

15 Temperature [ C] Electronics (1.8mm) Inlet tube (1.8mm) Outlet tube (1.8mm) Pressure [Bar] Delta T (`C) & Delta P(Bar) Outlet tube (2mm) Comparison to test results CMS-B-PIX m = 1.48g/s Q total = 25.87W P in = 2.40Bar T in = C dp =.33Bar dt = 10.8 C Exp. Wall Temperature Theory Wall Temperature Theory CO 2 Temperature Theory CO 2 Pressure IBL temperature and pressure profile. MF=1.1g/s, Tsp=-2.71ºC, Q=73.5, x end = Atlas-IBL Detector (1.5mm) dt Tube wall (ºC) dt Fluid (ºC) dp Fluid (Bar) CMS detector (1.4mm) Inlet tube (1mm) Outlet tube (3mm) Loop Length [m] Branch length (m) Figure 8: Temperature and pressure test results of the CMS pixel upgrade cooling branch (left) and the Atlas IBL cooling branch (right). Comparison with the CoBra calculator showed that the calculator is a promising tool for predicting the temperature and pressure gradients over long length cooling branches. Figures from: DESIGN CONSIDERATIONS OF LONG LENGTH EVAPORATIVE CO2 COOLING LINES Bart Verlaat and Joao Noite, GL-209, 10th IIF/IIR Gustav Lorentzen Conference on Natural Working Fluids, Delft, The Netherlands

16 Temperature ( C) Pressure (Bar) Pressure Heater What circulation method can we use? Liquid Vapor Refrigeration method: (Atlas) Vapor compression system Compressor 2-phase BP. Regulator Warm transfer Enthalpy Cooling plant Detector What happens inside a cooling tube? Heating a flow from liquid to gas Liquid Liquid Superheating Enthalpy (J/kg) Low ΔT 2-phase Isotherm Gas Increasing ΔT (Dry-out) If we remember slide 3, we see that proper cooling takes place on the liquid side, while compressors need gas as input. It is better to invent a cycle staying on the liquid side. => externally cooled pump cycle. Sub cooled liquid Target flow condition 2-phase liquid / vapor Dry-out zone 3 Super heated vapor

17 Pressure New cycle for particle detectors: 2PACL (The 2-Phase Accumulator Controlled Loop ) 2PACL method: (LHCb) Pumped liquid system, cooled externally Liquid Vapor Compressor Pump 2-phase Enthalpy Chiller Liquid circulation Cooling plant Cold transfer Detector The 2PACL has the following advantages: Cycle stays on the liquid side, no heat required (experiment can be cooled unpowered and no control heaters required) Evaporator pressure=(temperature) controlled with a 2-phase vessel away from the experiment. No local control nor sensing needed! All control hardware in a distant accessible cooling plant Primary cooling can be anything, no accurate temperature control needed as long as it is colder than the 2PACL 2-phase temperature. Inlet fluid state defined by physics => saturated liquid. Large temperature range (typical from room temperature down to -40 C) 17

18 Condenser 2PACL application in a particle detector Cooling plant (controls & actuators) in a safe and accessible area Shielding wall Only passive piping in detector area. Manifolds in accessible locations. HFC Chiller P 7 2-Phase Accumulator Heat in Long distance (50-100m) 5 Evaporator inside detector (4-5) P Pump Transfer line (Heat exchanger) Capillaries (3-4) for flow distribution 4 18

19 Pressure 2-Phase Accumulator Controlled Loop (2PACL) Liquid phase (Evaporation) Gas Pressure control with accumulator. Change set-point &5 Red dot (detector) on saturation line. Isothermal line 7 Enthalpy Pump

20 Pressure 2-Phase Accumulator Controlled Loop (2PACL) Liquid phase (Evaporation) Gas Lowering saturation pressure 7 1 4&5 Red dot (detector) follows saturation line. Isothermal line Cooling 7 Enthalpy 5 Pump

21 Pressure 2-Phase Accumulator Controlled Loop (2PACL) Liquid 2-phase (Evaporation) Gas Lowering saturation pressure &5 Red dot (detector) follows saturation line. Isothermal line Cooling 7 Enthalpy 5 Pump

22 Pressure 2-Phase Accumulator Controlled Loop (2PACL) Liquid 2-phase (Evaporation) Gas 2 3 Red dot (detector) follows saturation line. Lowering saturation pressure 7 1 4&5 Isothermal line Cooling 7 Enthalpy 5 Pump

23 Pressure 2-Phase Accumulator Controlled Loop (2PACL) Liquid 2-phase (Evaporation) Gas 2 3 Set point reached 7 1 4&5 Isothermal line 7 Enthalpy Pump

24 Pressure 2-Phase Accumulator Controlled Loop (2PACL) Liquid 2-phase (Evaporation) Gas 2 3 Red dot (detector) follows saturation line. Increasing saturation pressure 7 1 4&5 Isothermal line Heating 7 Enthalpy 5 Pump

25 Pressure 2-Phase Accumulator Controlled Loop (2PACL) Liquid 2-phase (Evaporation) Gas Increasing saturation pressure &5 Red dot (detector) follows saturation line. Isothermal line Heating 7 Enthalpy 5 Pump

26 Pressure 2-Phase Accumulator Controlled Loop (2PACL) Liquid phase (Evaporation) Gas Increasing saturation pressure 7 1 4&5 Red dot (detector) follows saturation line. Isothermal line Heating 7 Enthalpy 5 Pump

27 Pressure 2-Phase Accumulator Controlled Loop (2PACL) Liquid phase (Evaporation) Gas Set point reached 7 1 4&5 Isothermal line 7 Enthalpy Pump

28 Pressure 2-Phase Accumulator Controlled Loop (2PACL) Liquid phase (Evaporation) Gas Switching on detector 7 1 4&5 Red dot (detector) evaporation starts. Isothermal line 7 Enthalpy Pump Heat 28

29 Pressure 2-Phase Accumulator Controlled Loop (2PACL) Liquid phase (Evaporation) Gas Powering detector Red line (detector) in evaporation. Isothermal line Cooling 7 Enthalpy Pump Heat 29

30 Pressure 2-Phase Accumulator Controlled Loop (2PACL) Liquid phase (Evaporation) Gas Powering detector Red line (detector) in evaporation Isothermal line Cooling 7 Enthalpy Pump Heat 30

31 Pressure 2-Phase Accumulator Controlled Loop (2PACL) Liquid phase (Evaporation) Gas Detector is on Red line (detector) in evaporation Isothermal line 7 Enthalpy Pump Heat 31

32 Pressure 2-Phase Accumulator Controlled Loop (2PACL) Liquid phase (Evaporation) Gas Unpowering detector Red line (detector) Evaporates. Isothermal line Heating 7 Enthalpy Pump

33 Pressure 2-Phase Accumulator Controlled Loop (2PACL) Liquid phase (Evaporation) Gas Detector power is off 7 1 4&5 Isothermal line 7 Enthalpy Pump

34 CO 2 cooling projects in particle physics 2 CO 2 cooling systems have successfully been built for particle detectors AMS-Tracker experiment on the International Space Station LHCb-Velo experiment for the Large Hadron Collider at CERN Many future CO 2 cooling systems are under design: Atlas Inner CERN CMS upgrade CERN KEKb (Japan) Some are foreseen for the far future: CMS upgrade CERN Atlas upgrade pixel and CERN LC-TPC for the future Linear Collider 34

35 The 1 st CO 2 cooling system in Space! A CO 2 cooling system for Alpha Magnetic Spectrometer (AMS) Tracker Detector on the International Space station (ISS) CO 2 cooling radiator AMS in the Shuttle (STS-134, May 2011) AMS on the ISS 35

36 MAGNETE AMS-Tracker Thermal Control System (AMS-TTCS) RADIATORE condensatori 144 WATT TRD TOF Primary cooling not needed in space as environment is cold. Direct radiation to space TRACKER TOF RICH ECAL 150 Watt detector with evaporator rings Cooling system component boxes (1 redundant) 3

37 AMS-Tracker with CO 2 cooling rings. Tracker connections Inner plane thermal bars and hybrids Inner plane evaporator rings Inner plane silicon ladders 37

38 Temperature ( C) AMS TTCS Cooling performance in space (1) 10 5 Evaporator partly single phase (gradients) Accumulator set point change 0 Evaporator fully 2-phase Heat exchanger heating Pump inlet (PT02_P) Accumulator (PT01_P) Evaporator inlet (DS13-P) Evap 1 (SensE) Evap 2 (SensG) -15 Evap 3 (SensF) orbit (~1.5hour) 13:00 15:00 17:00 19:00 21:00 23:00 01:00 Varying CO 2 liquid due to orbital fluctuations Time(HH:MM) 38

39 08/0/11 10/0/11 12/0/11 14/0/11 1/0/11 18/0/11 20/0/11 Temperature ( C) 20 AMS TTCS Cooling performance in space (2) Detector switched-off Soyuz docking Solar Panel orientation change Pump inlet (PT02_P) Accumulator (PT01_P) Evaporator inlet (DS13-P) Evap 1 (SensE) Evap 2 (SensG) -15 Evap 3 (SensF) Magnet Average Date (DD/MM/YY) 39

40 AMS TTCS Cooling performance in space (3) month stable at 0⁰C despite cold low beta periods 40

41 Ca. 100m CO 2 cooling projects in LHC VELO detector: 1.5 kw@-30 C (Running successfully since 2007) Atlas IBL: 1.5 kw@-40 C (Operational 2013) 27 km LHC CMS pixel: 15 kw@-20 C (Operational 2014) 41

42 LHCb-Velo Thermal Control System (LHCb-VTCS) Evaporator Passive tubing only Transfer tube Concentric assembly Cooling Plant All active hardware Cooling capacity: 1.5 C 42

43 VTCS Evaporator 43

44 Condenser Restriction Temperature( C), Level(%) Temperature( C), Level(%) Temperature( C), Level(%) Heatload (W) Start up of the VTCS during October commissioning: 8:40 - Start-up with set-point -5 C 11:10 - Detector switched on 0 12:50 Set point to -15 C 15:30 - Set point to -25 C 50 17:10 - Set point to -30 C 18:20 - Set point to -35 C (System Limit) 19:10 - Set point to -34 C 40 19:30 - Set point to -25 C 20:00 - Detector Switched off Accumulator Set-point temperature Silicon temperature ( C) ( C) Pump liquid Accumulator temperature Set-point ( C) temperature Evaporator ( C) saturation Pump liquid temperature ( C) VTCS Commissioning results: Start-up and operation ator Set-point temperature ( C) Pump liquid temperature ( C) Evaporator saturation temperature ( C) Accumulator liquid level (%) Detector heat load (W) Accu liquid level 10-Accumulator set-point Detector power A-Silicon temperature 9-Pumped liquid gas 10 Accumulator :00 12:00 15:00 18:00 21:00 01-Oct-2009 Time (hh:mm) Silicon temperature ( C) Accumulator Set-point temperature ( C) Pump liquid temperature ( C) Evaporator saturation temperature ( C) Accumulator liquid phase Cooling plant area Transfer lines (Ca m) VELO area Evaporator / Modules C SP R507a chiller C SP gas 2-phase 9 Pump Concentric tube A C SP 44

45 Pressure (Bar) T=-40 C VTCS Commissioning results: Start-up and operation in the PH-diagram SP=21 C (Start-up) 9-Pump inlet Liquid T=20 C Start-up sequence 1. Increase pressure to make liquid. SP=-5 C Freezing (Solid/Liquid) SP=-15 C T=0 C T=-20 C 2. Pump at high pressure and cool down in liquid mode 3. Lower pressure to desired set-point 4. Power-up detector SP=-25 C SP=-30 C SP=-35 C 2-Phase (Liquid/Vapor) T=-40 C Switch-off detector Lowest possible set-point (liquid approaches saturation line) Enthalpy (kj/kg) 45

46 Atlas IBL-cooling system (1) IBL detector: Ø80mm x 800mm C 14 staves with 1 cooling pipe New detector with smaller beam pipe in space of current beam pipe Carbon foam structure 1.5mm ID titanium cooling pipe Pixel detector chips (70watt/stave) 4

47 CMS upgrade pixel cooling system Replacement and upgrade of current pixel detector -20ºC Very long serial lines with relative high heat flux F-PIX (Forward) 47

48 KEK Belle-2 SVD and PXD Belle-2 PXD and SVD, 1.5 Common CO 2 cooling plant development with Atlas IBL Belle-II SVD detector Belle-II pixel detector (Rapid Prototyping heat sink) 48

49 CO 2 cooling support Traci Cora Marco To support the CO 2 cooling projects in particle physics several test systems are under development: Cora (CO 2 Research Apparatus) Fixed test plant for CERN based research (0-2kW, +20 to -35ºC) Marco (Multipurpose Apparatus for Research on CO 2 Fully automatic (User friendly) CO 2 test system for general use (0-2kW, +20 to -45ºC) Base design for future on detector cooling plants (Atlas IBL, Belle-2) Traci (Transportable Refrigeration Apparatus for CO 2 Investigation) Small test system for laboratory use New simplified 2PACL concept to reduce cost and complexity (0-350W, +20 to -40ºC) 49

50 Accumulator Temperature ( C) TRACI Transportable Refrigeration Apparatus for Co 2 Investigation Experiment connection 4 5 Flow regulation TRACI layout P,T CO2 Chart liquid temperature Title (at pump) CO2 temperature Accumulator saturation temperature Experiment venting Local experiment box Concentric hose P W on Power off 150 W on condenser compressor P 5 TEV R404a Chiller T Heater T R404a evaporator/ CO 2 condenser T 1 CO 2 pump T CO 2 loop -50 9:00 10:30 12:00 13:30 15:00 1:30 Time (hh:mm) TRACI: A simplified new concept for providing a conditioned CO 2 flow for cooling research. 2PACL principle simplified (few functions have been integrated) Integrated 2PACL (I-2PACL ) Patent of I-2PACL concept filed Goal: An easy to (mass) produce user friendly system Operational from +25⁰C to -40 ⁰C Initial cooling power up to 350 Watt (depending on minimum temperature)

51 The TRACI factory Prototypes are already mass produced 2 have been build (Atlas & LHCb) 3 under construction (Atlas, CMS & Nikhef/AIDA for development) Investigating a start-up company for real production 51

52 TRACI a modular design Commercial chiller CO 2 piping in a 2Dfoambox User interface: On/off and reset buttons Error indication Pressure controller Control: Simple conditioner and relay logic 52

53 MARCO Multipurpose Apparatus for Research on CO 2 MARCO is prototype CO 2 2PACL system for multipurpose use. User friendly Automatic experiment connection Automatic filling Designed according to CERN experiment standards. Baseline concept for the detectors IBL (CERN) and Belle-2 (KEK), common development with MPI-Munich. PVSS-Unicos control interface Low temperature design 2kW@-45ºC Frequency controlled 2-stage chiller 53

54 MARCO production Controls build at CERN-DT 2-stage chiller for IBL temperatures from ECR-Nederland A CO 2 2PACL build in MPI 54

55 Conclusions CO 2 is a very good candidate fluid for applications were limited cooling space is available or limited additional mass is allowed. CO 2 cooling is a good candidate if high power densities are present and an isothermal heat sink is required CO 2 cooling is widely accepted in Particle Physics community as the future cooling method for the inner silicon detectors. The 2PACL concept has proven to be a good method for controlling evaporation conditions in distant set-ups 2 CO 2 systems are operational in particle physics and perform well. Several new systems are under development including systems for testing 55

56 Questions? It s cold here, can you turn the cooling off? 5