CMS CO2 Test Stand Specifications and Installation Status Erik Voirin Fermilab PPD - Process Engineering Group CMS CO2 Cooling Test Stand1

1

CMS CO2 Test Stand Specifications and Installation Status

Erik Voirin Fermilab

PPD - Process Engineering Group

CMS CO2 Cooling Test Stand

2

CMS CO2 Cooling Plant Specs• Closed Loop System cooled by three staged condensing units.

• Can provide 0 - 20kW of cooling depending on CO2 temperature.

• Cooling Power: 0-8kW@-40C; 0-13kW@-30C; 0-20kW@-20C.

• Carbon Dioxide Flow: Variable speed pumping to 2250 grams/sec.

• System contains 135kg of CO2 and is rated to 84 bar.

• Numerous connection points for small or large scale CO2 cooling experiments.

• Controlled by PLC through touch screen or network.

• Equipped with hazardous environment / CO2 air level monitors and safety alarms.

• Status: In final installation and commissioning phase.


3

CMS CO2 System Simple Overview


4

Installation / Commissioning Status

• Mechanical installation complete, except forsome pipe insulation

• PLC and all instruments

installed & commissioned

• 3 Condensing units nowbeing charged with R404a


5


• Cross Shaped Storage Vessel in place and insulated with 4” Trymer insulation.

• Storage Capacity is 625 Liters.

• 135kg CO2 @ 35C


6


• PLC Logic complete and touch screen controller programmed

• All hardware (heaters, pump, chillers, valve, fan)are controlled by the PLC

• Must complete insulationfill system with CO2

tune controls and testsystem under load.


7

Pressure/Leak Testing• Thread sealants rated to 10,000 psi fail at 1200 psi.

– (Teflon tape and Pipe Dope compounds)

• System was completely leak tight at 300 psi. • Raised pressure to 1320 for pressure test, (Passed)

– Bubble test at 1200 psi showed every single NPT fitting leaked.

• Used 3M Scotch-Weld Structural Adhesive– 3M Pt#1838 Green

• All No Leaks except for all three of the largest fittings (1.25” NPT)• Cleaned threads with alcohol, applied the adhesive to both male

and female threads, retighten.• 4 day high pressure leak test at 950 psi showed no leaks and no

drop in pressure.


8

Control System Interface – Main Overview• Touch screen and remote control and monitoring


9

Control System– Temperature Control• Set Storage Tank CO2 Temperature


10

Control System– Pump Control• Set differential pressure across experiment


11

FPIX Calculations and Characteristics of Single and Two Phase Flow

Erik Voirin Fermilab

PPD - Process Engineering Group


12

FPix Mass Flow at 3.8 bar DP


1 OO 1 OI 1 II - IO 2 OO 2 OI 2 II - IO 3 OO 3 OI 3 II - IO0

1

2

3

4

5

6

7

8

Mas

s flow

at 3

.8 b

ar d

iffer

entia

l (g/

s)

Route Flow (grams/sec)1 OO 6.4021 OI 6.857

1 II - IO 6.1782 OO 6.5142 OI 7.205

2 II - IO 6.363 OO 6.8573 OI 7.437

3 II - IO 6.605Half Cylinder 60.415

Total 241.66

13

Pressure along routes of half disk Starting sub-cooled at 23.5 bar and -20C


0 1000 2000 3000 4000 5000 600017

18

19

20

21

22

23

24

Half Disk 1

CO2 Pressure O-O (6.402 g/s)

CO2 Pressure O-I (6.857 g/s)

CO2 Pressure Inner (6.178 g/s)

Length from manifold (mm)

CO2

Pres

sure

14

Temperatures along routes of half disk Starting sub-cooled at 23.5 bar and -20C


0 1000 2000 3000 4000 5000 6000-20

-19.5

-19

-18.5

-18

-17.5

-17

-16.5

Half Disk 1

CO2 Temp O-OCO2 Temp O-ICO2 Temp Inner


CO2

Tem

pera

ture

15



0 1000 2000 3000 4000 5000 6000-20

-19.5

-19

-18.5

-18

-17.5

-17

-16.5

Half Disk 2



CO2

Tem

pera

ture

16



0 1000 2000 3000 4000 5000 6000-20

-19.5

-19

-18.5

-18

-17.5

-17

-16.5

Half Disk 3



CO2

Tem

pera

ture

17

Vapor Quality

• Exit Quality is roughly 1%• Saturation doesn’t begin until partway into the

half disk• High flow rate still yields a high convection

coefficient in single phase flow (~16 kW/m2*K)– Results in a maximum bulk CO2 to tube wall

temperature difference of 0.8C, 1.4C, 0.9C on Outer-Outer, Outer-Inner, and Inner tubes. (130% load)


18

Preheating to Saturation• Not recommended as a sole solution to achieve saturation, as it causes a

sharp rise in fluid temperature, resulting in reduced performance.


19

Sub-cooled boiling• Wall boiling

can occur before bulk fluid reaches saturation

• Two phase correlations for heat transfer shouldn’t be used at the ~1% quality which could be seen in FPix

• Second Putenkov equation

gives most accurate results for these micro channel tubes with near single phase flow.


20

Lowering Temperature• Preheating to achieve saturation results in larger peak in temperature.• Adding a needle valve before flow enters the cooling tubes will reduce the

pressure and temperature. It will also raise the quality and decrease the flow rate.

• This would lower the temperature peak seen in the graph and move it to the left since we come closer to saturation by reducing pressure, not increasing temperature.

• Could be dialed in upon commissioning.• For lowest temperature the lowest

pressure difference from the detector outlet back to the storage tank is preferred. (NO OUTLET RESTRICTIONS)


21

Needle Valve/Pre-Heater Optimization• Attempting to calculate an optimal cooling scenario can only get us

close to a possible solution. (Actual heat loads are not uniform and involve gravitational and momentum effects)

• The pressure reducing valve assures we can tune our cooling tubes to get the absolute maximum possible performance with our given inlet and outlet conditions.

• Can be combined with a pre-heater if needed.

• This will allow us to tune the system to run at any differential pressure, any differential temperature, any flow rate, and any quality possible with our given inlet and outlet conditions.


Documents

CMS CO2 Test Stand Specifications and Installation Status Erik Voirin Fermilab PPD - Process Engineering Group CMS CO2 Cooling Test Stand1