news on the co 2 cooling developments at cern dt cms tracker upgrade cooling and mechanics meeting
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[email protected] 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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news on the co 2 cooling developments at cern dt cms tracker upgrade cooling and mechanics meeting

[email protected]

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

Liquid

Liquid

Vapor

Vapor

Pressure

Pressure

2

2

1

1

2-phase

2-phase

4

4

5

3

3

Enthalpy

Enthalpy

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.
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

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)

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

Liquid

Liquid

Vapor

Vapor

Pressure

Pressure

2-phase

2-phase

Enthalpy

Enthalpy

slide14

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

[email protected]ºC vs 1.2 [email protected]ºC

2 vs 1 pump

the portable 100w mini xxxxx system
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 [email protected] -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
  • 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 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.
matlab state point model
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 ([email protected]), Model currently works with old models (Friedel & Kandlikar from the LHCb-velo stone ages)

typical state point model output lhcb velo
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

summary
Summary
  • 2 operational CO2 systems @ CERN
  • 2 new laboratory CO2 systems under development ([email protected] -40°C & [email protected] -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
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