1. Cooling R&D at RWTH Aachen Lutz Feld, Michael Wlochal (RWTH Aachen University) CEC Meeting, CERN 21. 4. 2009 Lutz Feld, Michael Wlochal (RWTH Aachen University) CEC Meeting, CERN 21. 4. 2009

2. Outline of R&D Program 21. 4. 2009Lutz Feld (RWTH Aachen University)2 o thermal design of SLHC tracker – module and super-module thermal design – design and optimization of thermal interfaces – precise measurements of thermal gradients – evaluation of new materials – specification of the lowest possible operating temperature o properties and performance of a CO 2 cooling system – design, construction and commissioning of a re-circulating CO 2 cooling test system – according to Bart Verlaat (NIKHEF), who gave a lot of advice, a recirculating system is needed in order to achive stable operating conditions – investigation of operating conditions and performance as a function of temperature, load, time-dependent variations etc. – gain confidence in CO 2 cooling

3. 1 1 2 2 3 3 4 4 5 5 6 6 7 7 pre-cooling coolingheating Open CO 2 Cooling System: „Blow System“ 21. 4. 2009Lutz Feld (RWTH Aachen University)3 T = -40°C Room Temperature T = -40°C R R R R R R Power Supply CO 2 - Sensor Heating Heat Exchanger Balance 1 1 2 2 3 3 4 4 5 5 6 6 7 7 50…200 W CO 2 Rupture Disk 80 bar Vent Bypass Rupture Disk 20 bar Valve to keep pressure at points (3)-(6) at saturation vapour pressure at cooling temperature Valve to control CO 2 flow rate Rupture Disk 20 bar insp. glass

4. 1 1 2 2 3 3 4 4 5 5 6 6 7 7 pre-cooling coolingheating CO 2 Enthalpy Pressure Diagram CO 2 Enthalpy Pressure Diagram: „Blow System“ 21. 4. 2009Lutz Feld (RWTH Aachen University)4 liquid + gas gas dry ice liquid

5. CO 2 Enthalpy Pressure Diagram CO 2 Enthalpy Pressure Diagram: Re-Circulating System 21. 4. 2009Lutz Feld (RWTH Aachen University)5 liquid liquid + gas gas dry ice 1 1 2 2 4 4 5 5 6 6 4 -> 5: detector load QQ 3 3 QQ

6. heat removal design considerations o load: 500 W maximum o CO 2 temperature at detector: -45°C … +20°C o precise temperature control o precise flow measurement o continuous operation o safe operation (100 bar max.) chiller temperature  vapour pressure  evaporation temperature Re-Circulating CO 2 Cooling Test System 21. 4. 2009Lutz Feld (RWTH Aachen University)6 1 1 2 2 3 3 5 5 6 6 4 4 1 1 2 2 4 4 5 5 6 6 pump sub-cooled liquid 4 -> 5: detector load QQ 3 3 Pressure Enthalpy QQ Chiller 2 Chiller 1 flow meter

7. Implementation of Re-Circulating CO 2 Cooling Test System 21. 4. 2009Lutz Feld (RWTH Aachen University)7 Components Chiller 1: Huber Unistat 815 (1.2 kW@-60C) Chiller 2: Huber CC-505 Expansion Vessel: Swagelok 304LHDF4-1Gal Levelmeter: Rechner Sensors KFS-1-500-365-PEEK-VA-3/4“ Heat Exchangers: SWEP B16DWx8/1P-SC-U Pump: GATHER 1MX-X/12-11/X-SS/S/Q/K200/HDT/DS2D50 Flow Meter: Rheonik RHM015-T2-P1-SM0-M0-G1-N Piping, fittings etc.: Swagelok Frame: ITEM Temperature Probes: various

8. Status & Plans o most components for re-circulating CO 2 cooling test system have been delivered o system should be operational by June o connect to pipe with dummy loads and temperature probes o then perform tests of the cooling system – test the system under variation of load and temperature – test reliability and failiure modes o then perform thermal and hydraulic measurements of – pipes – interfaces – detector modules – super-modules 21. 4. 2009Lutz Feld (RWTH Aachen University)8

9. Questions to be answered About the cooling system: o Does the system operate reliably – over the full detector temperature range -45°C … +20°C ? – over the full detector load range 0 W … 500 W? o What are the time constants – at start-up? – when temperature is changed? – when the load is changed? About the detector system: o What are the thermal / pressure gradients along straight and bent pipes of various diameters? o Does gravity have a negative impact on the cooling system performance? o What is the optimal (i.e. low thermal resistance and low mass) interface between a 1-2 mm diameter cooling pipe and a detector module? o What is the optimal contact area for a given heat load?  requires rather acurate temperature measurements and stable system behaviour 21. 4. 2009Lutz Feld (RWTH Aachen University)9