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Bart Verlaat 13 October 2010

bverlaat@nikhef.nl. News on the CO 2 cooling developments at CERN DT CMS Tracker Upgrade Cooling and Mechanics meeting. Bart Verlaat 13 October 2010. Status of the current CO 2 systems: Blow system. Joao’s blow system:

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Bart Verlaat 13 October 2010

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  1. bverlaat@nikhef.nl News on the CO2 cooling developments at CERN DTCMS Tracker Upgrade Cooling and Mechanics meeting Bart Verlaat 13 October 2010

  2. Status of the current CO2 systems: Blow system • Joao’s blow system: • Blow system was upgraded with a 2nd blow branch to create the ability to have more latent heat or sub cooling. External sub cooling Internal sub cooling Liquid Liquid Vapor Vapor Pressure Pressure 2 2 1 1 2-phase 2-phase 4 4 5 3 3 Enthalpy Enthalpy

  3. Status of the current CO2 systems: Cryo lab 2PACL • Operational status: • Operational status discussed in Thorsten’s presentation. • Some modifications done by Joao: • The system had problems with small flows (Large heat leak & low flows = high temperature differences or unwanted boiling) • System was modified to run always at high flow, small flows to experiments are obtained by a metering valve in the experiment feed line. • Dummy heater was placed in a 2nd by-pass. • Metering valves were installed in the by-passes to create more pump pressure. • The R404a compressor unit works stable under high heat loads. The dummy heater in the by-pass can now be used to increase the cooling load for a stable chiller operation (=stable evaporator with current accumulator). • Accumulator was ready but had problems with certification. • End flanges were made from a wrong steel grade: ~303 instead of 316L. (certificate showed the 316L). Error was found during the final material sample analyses. • Accumulator is remanufactured. Delay is unknown up to now.

  4. New developments in CO2 cooling • A few new CO2 cooling developments are ongoing in CERN-DT. • Development of a 2 multipurpose CO2 coolers for general use based on the 2PACL principle (LHCb and AMS systems). • A “portable” air-cooled 100Watt system • A “not so portable” water cooled 1kW system • Operational temperature range of both systems: -40°C to +25°C evaporative temperature. • Development of new concepts • Making the system simpler (portable system) • To reduce accumulator volume (important for large scale systems) • Contribute to concepts for future systems • CMS pixel / upgrade • Atlas IBL / upgrade (SR1-cooling plant)

  5. The 1kW “xxxxx” system We are still looking for a name. 1 bottle of wine if you come up with the winning name! • Development of the kW system is in close cooperation with Nikhef. • Nikhef is developing a CO2 cooler for the XFEL detector at DESY. A common design is made as specs are (almost) identical. • Concept is to make them from a user stand point as simple as possible. Basic CO2 cooling knowledge required. • 3 user input variables: • Evaporative temperature • Mass flow • Enthalpy (sub cooling or vapor quality for user) • 4 operation states: • Connecting experiment • Disconnecting experiment • Cooling experiment • (re) filling CO2 • User interface via integrated touch screen, connection of PVSS is optional but not required • This is all you can do with it! …… but must be enough to cool your won bottle of wine.

  6. xxxxx system

  7. Set-Point Controls Tsub = -50°C => Enthalpy=135 kJ/kg (Experiment sub cooling request) Pump sub cooling control Taccu+Tsub-10 => 20-50-10 = -40°C Heater = (Enth request - Enth 3) x Massflow 3 Taccu = 20°C Tsub = -50°C 10°C Heater = (Enth request - Enth 3) x Massflow Accumulator control (Pressure) 3 Taccu = -20°C Pump sub cooling control Taccu+Tsub-10 => -20+0-10 = -30°C VQ = 20% => Enthalpy=210 kJ/kg (Experiment vapor quality request)

  8. Accumulator design and control • Similar to VELO accumulator but with hot gas by-pass for chiller capacity control. • Temperature set-point with pressure control. • Volume ca. 5 liter (PED class II) • Discussion with CERN central workshop and safety for designing and construction of accumulators at CERN following the PED rules.

  9. CO2 condenser design and control • Alfa-laval AXP10-20 high pressure heat exchanger (120 bar) • CO2 sub cooled liquid control with R404a injection • Temperature set point of PID controller determined by system. • Tpumpinlet = Taccu + Tsubcooling – 10°C

  10. Pump mass flow control Single pump • Two pumps in series to boost pressure drop • Gather 1m-J/12-11/x-ss/s/q/k200/DLC gear pumps with integral DC drive • MassflowcontrolledwithRheonikmassflow meter Dual pump

  11. Condensing unit • Water cooled R404a or CO2 chiller • Frequency controlled compressor to minimize base load. • Investigating Sanyo 2-stage CO2 compressor with inverter for xxxxx cooler. • Frequency controlled Maneurop compressor selected for XFEL cooler. Test chiller is ordered for condenser control and hot gas by-pass tests.

  12. Enthalpy heater control • User input –yy to +xx -yy = subcooling (ºC), +xx = vapor quality (%) 0 = saturation line • Set points translated to enthalpy with respect accumulator pressure. • Heater power is calculated by input condition (Enthalpy point 3 and mass flow) -> No PID control. • DC-power for smooth heating (pulse heater influences mass flow and thus the heater control itself)

  13. xxxxx versus XFEL cooler CERN-DT xxxxx system Nikhef/Desy XFEL system Liquid Liquid Vapor Vapor Pressure Pressure 2-phase 2-phase Enthalpy Enthalpy

  14. Differences will be designed to be interchangeable: 1 common mechanical (and control?) design • Designer from Krakow will arrive • 1st of November at CERN. • Nikhef has also assigned 1 FTE. XFEL system Heater vs heat exchanger xxxxx system 1kW@-45ºC vs 1.2 kW@-25ºC 2 vs 1 pump

  15. The portable 100W “Mini -xxxxx” system • Development of the 100W system will be a simplified concept wrt the 1kW xxxxx system. Controls are reduced to a minimum. (Goal is no PLC). • Collaboration with LHCb for the VELO upgrade development. Raphael is working on design. • Volume is small so everything fits in the lowest PED class (Article 3.1). • The goal is to have 100W@ -40°C, and a temperature range between 25°C and -40°C. • Same pump and heat exchanger type as xxxxx system, but smallest in range.

  16. Future developments • Future systems will have a large increase of power and volume. • Especially large volume pipes (reuse of CMS pipes) will demand for large volume accumulators. • The CMS low pressure requirement, requires emptying of the system at standstill. This demands for even larger accumulators. • Therefore room temperature accumulation is under study.

  17. 2PACL State point model in Matlab • To support future system development a simulation is developed in Matlab to study state point values of a full loop. • At each state point the pressure and enthalpy are calculated iteratively according to the properties at the given state-points. Integrated Refprop database • Model can be sub divided in small sections of dL to accurately calculate the fluid state at any place in the loop. Environmental heat is included. • General configuration file as input giving tube information (lengths, diameter and isolation), flow restrictions (Cv), heat exchange(external or internal), pump performance.

  18. Matlab state point model Qx= Qapplied + Qenvironment +Qexchanged Qx+1 dPx+1 dHx+1 dPx= f(D,Q1,MF,VQ,P,T) or f(Cv) dHx= Qtot/MF or pump work Px,Hx Px+2,Hx+2 Px+1 = Px- dPx Hx+1 = Hx+ dHx Tx,VQxand properties derived from Refprop dPpump=∑dPall dHcondenser = ∑dHall Current status: All latest Thome models (dP, HTC) are being implemented (Joao@portugal), Model currently works with old models (Friedel & Kandlikar from the LHCb-velo stone ages)

  19. Typical state point model inputExcel configuration file

  20. Typical state-point model output (LHCb-VELO) Tsub=-40°C, Taccu=26°C Tsub=-40°C, Taccu=-10°C Tsub=-40°C, Taccu=-30°C State points in PH-diagram Subdivision details of transfer line

  21. Summary • 2 operational CO2 systems @ CERN • 2 new laboratory CO2 systems under development (1kW@ -40°C & 100W@ -40°C) • Scaling up 2PACL for the future • Prototyping of different concepts • Development of a state point model with latest Thome models to investigate new cycles

  22. bverlaat@nikhef.nl

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