Development of a Mechanically Pumped Two-Phase CO 2 Loop for the AMS-2 Tracker Thermal Control System

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1 Development of a Mechanically Pumped Two-Phase CO 2 Loop for the AMS-2 Tracker Thermal Control System A.A.M. Delil National Aerospace Laboratory NLR P.O. Box 153, 8300 AD Emmeloord, Netherlands phone , fax adelil@nlr.nl AMS TIM Meeting Boston January 23rd 2002

2 AMS-2 Silicon Tracker Responsibles Tracker Thermal Control System (TTCS) Team NLR, Amsterdam, The Netherlands TTCS Development PM: A. A.M. Delil LPM of TTCS Development & Tracker Overall Thermal Modelling: A.A. Woering Thermal Modelling: A. Pauw Simulation Loop, Components, Experimenting: A.W.G. de Vries, G. van Donk, A. Pauw Thermal Vacuum Test Plan: J.J.M. Prins NIKHEF, Amsterdam, The Netherlands TTCS Internal & Loop Development, Thermal Modelling, Simulation Loops: B. Verlaat CO 2 & PumpsConsultancy: H. Boer Rookhuizen INFN, Perugia, Italy Tracker Overall Responsible, Co-ordination: R. Battiston University of Geneva, Switzerland Co-ordination Tracker Internal: Mechanics/Interfaces/Integration: M. Pohl, E. Perrin 3

3 AMS-2 6

AMS-Silicon Tracker Thermal Requirements Silicon wafer thermal requirements: Operating temperature: -10 ºC / +25 ºC Survival temperature: -20 ºC / +40 ºC Temperature stability: 3 ºC per orbit Maximum

4 AMS-Silicon Tracker Thermal Requirements Silicon wafer thermal requirements: Operating temperature: -10 ºC / +25 ºC Survival temperature: -20 ºC / +40 ºC Temperature stability: 3 ºC per orbit Maximum accepted gradient between any silicon: 10.0 ºC Dissipated heat: 2.0 Watt EOL Overview of the main thermal components in the AMS-Tracker Hybrid circuit thermal requirements: Operating temperature: -10 ºC / +40 ºC Survival temperature: -20 ºC / +60 ºC Dissipated heat: 192 Watt total, 1 Watt per hybrid pair 7

5 Merits of Two-Phase Thermal Control Q=m(Xh lv + C p T), where T = T source T sink. h lv = J/kg and C p = 4780 J/kg.K for ammonia at 300 K. Since X = 0 in a single-phase loop and X = 1 (at maximum) in a twophase loop, the ratio of single-phase and two-phase mass flow rates is for ammonia / T. This implies for the two-phase loop case: considerably smaller, thinner, hence lower mass, system lines and smaller, lower power pumps, yielding far less undesired vibration impact on the micro-g level needed for proper experimentation. To minimise radiator area and mass, the temperature drop along the loop should be as small as possible. This drop is 1 to 2 orders of magnitude smaller in the two-phase case. The two-phase loop is almost isothermal (except the pulsating, vapour pressure driven loop). The latter is very important in case of a series configuration: All dissipating or heat requiring stations are almost at the same temperature, and do not depend on behaviour of preceding stations (like in the single-phase case). 8

6 Proposed Baseline Design Concept Series Configuration Two-Phase Mechanically Pumped Loop Compatible with existing AMS-Tracker hardware. Minimised material inside or near the tracker acceptance. Directly connected to the thermal bars, no additional heat collector needed. Multiple heat input possible, with minimum temperature gradients. Possibility of implementing a fully redundant system. Relatively low mass and costs. Drawback: Mechanical pump in a two-phase system. 9

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8 Serial CO 2 Two-Phase MPL Merits of Carbon Dioxide CO 2 currently is considered to replace freon-like refrigerants, as it is environment friendly and non-toxic. It is used for cooling in nuclear power plants as it is inert for radio-active radiation. For AMS this means no ISS safety-related problems! CO 2 has a very low liquid/vapour density ratio O(1-10), being crucial for a series 2-phase system. Ammonia: O( ). CO 2 cooling is proposed to be used in LHCb-Vertex by NIKHEF. Tests have proven concept feasibility. For the AMS-Tracker application, this means small tube dimensions (3 mm OD) in case of 2 loops, very low temperature differences (<1ºC), low pumping power (<10 Watt). 11

9 Properties of CO Phase Diagram Carbon Dioxide: Temperature - Pressure Diagram Melting Line Pressure, bar Solid Liquid Saturation Line Critical Point Sublimation Line Triple Point Vapor Copyright 1999 ChemicaLogic Corpo DrawnwithCO 2 Tab V Temperature, C Density of Vapour & Liquid Enthaplpy [kjoule/kg] Enthalpy Enthalpies liquid & / gas Evaporation and vaporization for Heat CO Temperature [ C] fluid vapor vaporization 12

Feasibility demonstration of the TTCS CO 2 MPL D A Q Tube 1 Tube 2 Tube 3 Tube 4 To gas heater, spring relieve valve and flow meter Pressure gauges CO 2 Bottle 99.

10 Feasibility demonstration of the TTCS CO 2 MPL D A Q Tube 1 Tube 2 Tube 3 Tube 4 To gas heater, spring relieve valve and flow meter Pressure gauges CO 2 Bottle Expansion % valve CO 2 Feasibility Test Set-Up Temperature gradient dt ('C) A1 (0.8 'C, 100 W, 1.7 g/s) A3 (3.2 'C, 100 W, 3.6 g/s) C1 (19.0 'C,100 W, 0.8 g/s) C2 (14.3 'C,100 W, 1.4 g/s) C3 (6.1 'C, 100 W, 3.2 g/s) C4 (0.4 'C, 200 W, 1.9 g/s) C5 (1.2 'C, 250 W, 2.6 g/s) C6 (2.5 'C, 360 W, 3.4 g/s) dt inlet (0m) dt tube 1 (1m) dt tube 2 dt tube 3 dt tube 4 (3.4m) (5.8m) (8.3m) dt outlet (9.3m) A A C C C C C C Feasibility Test Results Test Set-Up schematic 13

11 Heat transfer coefficient (W/m2K) Observed flow pattern 1 Watt, 4716 W/m2 2 Watt, 9432 W/m2 3 Watt, W/m2 4 Watt, W/m2 5 Watt, W/m2 0 Pure liquid Bubbly flow Annular flow Dry-out Vapour quality (-) Vapour quality and power dependence of the heat transfer coefficient and observed flow patterns, for a 2.5 mm ID tube at a flow rate of 2.7 g/s and a temperature of 278 K TTCS Test Loop Results Pressure drop (mbar) Liquid flow Watt Watt Watt Watt Watt X=0.5 (Dry-out limit) 100 X= Mass flow (g/s) Power Dependent Pressure/Temperature Drops for a 10 m long, 2.5 mm ID Evaporator at 273 K Evaporative temperature gradient ('C) Schematic of the TTCS Test Loop at NIKHEF. 14

12 AMS Silicon Tracker Thermal Control Phase 1 Results & Concluding Remarks Tracker cooling baseline: CO 2 two-phase serial MPL with dedicated low temperature (< say 270K) radiator. Simulation loop experiments with CO 2 has proven the feasibility for the 3-D tracker cooling line routing. Optimisation & control experiments with CO 2 and NH 3 are being done, after incorporating NLR components in the loop, i.e. a delta pressure sensor, a coriolis mass flow meter, view glasses for flow pattern observation, and a mechanical pump. Preliminary transient orbital heat sink calculations have been carried out for various radiator orientations. Transient radiator temperature calculations will follow for BOL & EOL conditions, and different thermal mass values. 15

13 NLR Joins AMS Collaboration to Experiment with TTCS Baseline Philosophy Minimum risk for Tracker and AMS Any period AMS is not active can be used for thermal experiments At least one week of thermal experiments during the first six months Adding minimum power and mass In principle no intrusion of the TTCS-loop TM/TC required 16

14 Critical Issues & Questions What do do if loop meets non-functioning at 278K? Slightly increasing set-point, as 288 K is not acceptable and it yields worse dt/dx in Tracker. Evaporator oscillations are: No issue in layout with 2 pumps. Damped in parallel operation by long lines with relatively large resistances. Condensers: Which one is active, what about freezing? Both are active, in accordance with the Tsink of the radiators. Freezing prevented by Overall System thermostat heaters. Control of TTCS (passively assisted by HX, liquid buffer, PCM) by: Set-point control by Peltier, most likely using a PID-type control algorithm. Electric pre-heater heating-up sub-cooled liquid to saturation Three-way valve for control of the flow through condensers (to be verified experiments). Pumping speeds control. FMECA/FTA study is to be done to compare separated versus connected loops. 18

15 Design Activities Evaporator Layout Radiator Layout Area, Orientation Shape: Curved versus Flat (Current Baseline) Condenser Layout (Radiator Shape Dependent) Condenser-Radiator Connection (Shape Dependent) De-Coupling of Primary and Back-up Loop 21

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18 MPL Evaporator Configuration 25

19 TTCS Radiator Concepts Flat radiator with straight heat pipes Sensible for puncture (no extra debris shielding possible other than the radiator itself) Relatively low costs Flat radiator with bent heat pipes Flat radiator with bent heat pipes Condensers can be optimally protected against debris: Extra debris shield possible, Condensers in the center Complex geometry yields high costs Integration problems Curved radiator with bent heat pipes Condensers have same protection as the flat version Simple geometry No severe integration problems foreseen Curved radiator shows slightly better performance 27

20 Bent Heat Pipe Radiator Concept Debris shield (0-70 mm) Aluminum radiator plate (0.5 mm) Embedded heat pipes (o12.5 mm) Primary loop condensers Back-up loop condensers Flat Heat Pipe Radiator Concept 28

21 Flat Radiator & Bent Heat Pipes 31

22 Curved Radiator with Bent Heat Pipes 32

23 TTCS Modelling Refinement Honey comb HP wall HP core 34

24 Modelling Refinement Activities: Radiator (Provisional) 35

25 Current Modelling Activities: Solving Differences with CGS Model -EqualEqual temperatures on radiators: only a single moment during orbit -Choose set-point (2φ,, X=0 in exit) -Do steady state calculation 38

26 Modelling Activities for Other Orbital Cases The many cases necessary to be calculated in addition to nominal case for the tracker (beta=0, MPA), are: Hottest and coldest cases Transfer phases Contingency cases 39

27 Breadboard Model Test Set-ups Preliminary Test Set-up Current BBM Layout 40

28 BBM Evaporators 41

29 Flat Condenser Element 43

30 Other BBM Components Liquid buffer PCM set-up 44

31 Breadboard Model Experiments BB set-up with real AMS dimensions & shapes Peak damping options: Liquid buffering Phase Change Material: Paraffin with appropriate melting temperature Active coupling of liquid line exiting the condenser, with the TTCS components-box Liquid Flow Metering Vapour Quality monitoring 45

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33 Redundancy Policy Failure Mode Effect & Criticality Analysis should provide all possible ways things can go wrong provides a possible solution, e.g. redundancy of the item Fault Tree Analysis should provide the probability of failure and the impact on the system provides the amount of redundant items optimises the design by checking the progression of component failures 48

34 Concluding Remarks TTCS development is in progress, but original concept of two complete loops (full redundancy) is under discussion, to realise AMS-2 mass reduction. The above may imply a reduction of reliability, increase of risk, reduction of lifetime and decrease of the planned NLR two-phase experiments. Nothing is sure, things are changing, but the manifest date hardly moves. 50

EVAPORATIVE CO 2 HEAT TRANSFER MEASUREMENTS FOR COOLING SYSTEMS OF PARTICLE PHYSICS DETECTORS

HEFAT21 7 th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics 19-21 July 21 Antalya, Turkey EVAPORATIVE CO 2 HEAT TRANSFER MEASUREMENTS FOR COOLING SYSTEMS OF PARTICLE PHYSICS