News on the co 2 cooling developments at cern dt cms tracker upgrade cooling and mechanics meeting
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News on the co 2 cooling developments at cern dt cms tracker upgrade cooling and mechanics meeting

News on the CO2 cooling developments at CERN DTCMS Tracker Upgrade Cooling and Mechanics meeting

Bart Verlaat

13 October 2010

Status of the current co 2 systems blow system
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




















Status of the current co 2 systems cryo lab 2pacl
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.

  • New developments in co 2 cooling
    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)

    The 1kw xxxxx system
    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.

    Bart verlaat 13 october 2010

    xxxxx system

    Set point controls
    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


    Taccu = 20°C

    Tsub = -50°C


    Heater = (Enth request - Enth 3) x Massflow

    Accumulator control



    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)

    Accumulator design and control
    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.

    Co 2 condenser design and control
    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

    Pump mass flow control
    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

    Condensing unit
    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.

    Enthalpy heater control
    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)

    Xxxxx versus xfel cooler
    xxxxx versus XFEL cooler

    CERN-DT xxxxx system

    Nikhef/Desy XFEL system











    Bart verlaat 13 october 2010

    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

    The portable 100w mini xxxxx system
    The portable 100W “Mini - mechanical (and control?) designxxxxx” 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.

    Future developments
    Future developments mechanical (and control?) design

    • 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.

    2pacl state point model in matlab
    2PACL State point model in mechanical (and control?) designMatlab

    • 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.

    Matlab state point model
    Matlab mechanical (and control?) design state point model

    Qx= Qapplied + Qenvironment +Qexchanged




    dPx= f(D,Q1,MF,VQ,P,T) or f(Cv)

    dHx= Qtot/MF or pump work



    Px+1 = Px- dPx

    Hx+1 = Hx+ dHx

    Tx,VQxand properties derived from Refprop


    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)

    Typical state point model input excel configuration file
    Typical state point model input mechanical (and control?) designExcel configuration file

    Typical state point model output lhcb velo
    Typical state-point model output mechanical (and control?) design(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

    Summary mechanical (and control?) design

    • 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

    Bart verlaat 13 october 2010 mechanical (and control?) design