Cooling R&D at RWTH Aachen Lutz Feld, Michael Wlochal (RWTH Aachen University) CEC Meeting, CERN Lutz Feld, Michael Wlochal (RWTH Aachen University) CEC Meeting, CERN

Outline of R&D Program Lutz 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

pre-cooling coolingheating Open CO 2 Cooling System: „Blow System“ Lutz 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 …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

pre-cooling coolingheating CO 2 Enthalpy Pressure Diagram CO 2 Enthalpy Pressure Diagram: „Blow System“ Lutz Feld (RWTH Aachen University)4 liquid + gas gas dry ice liquid

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

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 Lutz Feld (RWTH Aachen University) pump sub-cooled liquid 4 -> 5: detector load QQ 3 3 Pressure Enthalpy QQ Chiller 2 Chiller 1 flow meter

Implementation of Re-Circulating CO 2 Cooling Test System Lutz Feld (RWTH Aachen University)7 Components Chiller 1: Huber Unistat 815 (1.2 Chiller 2: Huber CC-505 Expansion Vessel: Swagelok 304LHDF4-1Gal Levelmeter: Rechner Sensors KFS 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

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 Lutz Feld (RWTH Aachen University)8

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 Lutz Feld (RWTH Aachen University)9