LHCb VELO Meeting LHCb VELO Cooling System Bart Verlaat (NIKHEF) 25 February 2003

LHCb VELO Cooling System Verification of the current design (As described in LHCb note XX/VELO, July 02,2001) 2001 status overview Primary cooling system (R404A/R507): -Capacity: 2.9 Secondary cooling system (R744=CO2): -Pmax: 70 bar -Qdetector: 2.5 kilowatt -CO2 mass flow: 17 g/s -Tevaporation: -30’C – 0’C - Warm transport lines. -Adjustable restriction in liquid transport line. -Fixed restriction before 0.9 mm tube: ca. 10 bar. -Heat exchanger between evaporator in and outlet after 1 st restriction. A F E D CB H I G 29 January 03

Secondary cooling system cycle in the P-h diagram (1). PointP (Bar)T (’C)H (J/g) A B C D E F G H I Mass flow12.15 g/s Volume flow0.66 l/min Liquid heater1466 Watt Gas heater396 Watt Total heater power1862 Watt Transport line pressure 70 bar Restrixction pressure drop 10 bar Detector evaporative temperature -30’C Detector power2500 Watt Liquid subcooling5 ‘C Minimum primary cooling capacity: 4362 Design status 2001 Heat exchanger: H FG =H CD Gas heater (GH) Liquid heater (AB) Detector power (EF) Pump (IA) 29 January 03

Modified status: -Heat exchanger before 1 st expansion valve -140 bar liquid transport Secondary cooling system cycle in the P-h diagram (2). PointP (Bar)T (’C)H (J/g) A B C D E F G H I Mass flow9.98 g/s Volume flow0.54 l/min Liquid heater1021 Watt Gas heater0 Watt Total heater power1021 Watt Transport line pressure 140 bar Restrixction pressure drop 10 bar Detector evaporative temperature -30’C Detector power2500 Watt Liquid subcooling5 ‘C Minimum primary cooling capacity: 3521 Heat exchanger: H FG =H AB Liquid heater (AB) Detector power (EF) Pump (IA) 29 January 03

VELO Cooling overview and optimization Warm transport has more impact on the design as foreseen, but is possible if: –The primary cooler capacity is increased. –The liquid transport pressure is increased (70 bar is in a very critical region) The efficiency of the system can be optimized by: –Keeping the secondary refrigerant flow (CO2) to a minimum (See table) –Moving the heat exchanger in the liquid line from CD to AB –Increasing the liquid transport pressure (Current pump limit is 140 bar) The evaporator flow conditions seem to be in the proper flow regime, but are more critical for dry- out in when the system is optimized. (x=0.83 w.r.t. x=0.68) ( “x” is the vapor quality). Tests have to determine the dry-out limit for the VELO evaporator flow conditions. If the heat exchanger stays in place the cold gas can be used to cool additionally heat sources on the VELOI. If not applied the cold gas will be heated electrically to avoid conde4nsation on the vapor line. 29 January 03 Results summary2001 Original Version2003 Optimized version Primary cooler capacitance ’C ’C Pump flow0.66 l/min0.54 l/min Detector vapor quality x (%)68%83% Fluid state in heat exchanger InletVapor/LiquidLiquid OutletVapor/Gas

Silicon Wafers thermal requirements: -Operating temperature range: -10 ‘C/ 0 ‘C LHCb /VELO -Survival temperature range: xx -Temperature stability: xx -Maximum accepted gradient between sensors: xx -Dissipated heat: 0.03W-0.17W (0.3 W max). LHCb /VELO Beetle chip thermal requirements: -Operating temperature range: xx -Survival temperature range: xx -Dissipated heat: 2500 Watt total. LHCb2001-0XX/VELO, July 02,2001 External electronics requirements: -External electronics dissipation: 1500 Watt (MVB) Other heat sources: -Corrugated foil heat dissipation: 2.2 Watt/Foil (FK) -Any other possible heat source??? Other temperature requirements: -Module base operational temperature: Assembly room temperature (ca. 20’C) (MD) -Corrugated foil: Lower than environment to get tension instead of compression. (HBR) -Any other temperature requirements??? LHCb environment temperature: 20'C? Any large amount of dissipation near the Vertex? 18 February 03 VELO thermal requirements:

Future activities (Very preliminary) The shown enthalpy cycles will be verified with a low power test set-up, using the existing AMS-TTCS CO2 system at NIKHEF. –Enthalpy measurements –Evaporator pressure drop measurements –Heat transfer measurements (Dry-out determination) Based on the test results a baseline design concept will be chosen. A BBM (Bread Board Model) will be built conform this baseline.