CO2 cooling pressure drop measurements

R. Bates, R. French, G. Viehhauser, S. McMahon

Objective

• Measure the pressure drops over our cooling pipes– Aim to measure straight pipe and compare to calculations– Our stave with its few wiggles– Pixel disk 1/12th – Change of pipe ID to understand this effect

• Measure the HTC of the CO2 system• Measure

– for warm running (commissioning)– cold operation (T=-25 to -35C)– function of massflow, power load, input vapour quality, pipe

inner diameter, pipe wiggles

Items to measure• Vapour quality at input 0 to x – we should understand the effect of a non-

zero Vi

• Vapour quality at output = 0.5• Enthalpy = 310J/g (at -35C) • Power = 170/100W (short and long stave) & ~100W for 1/12th of Pixel disk

– Detector power = 20W– Includes EOS card– Linear power density along pipe = 0.67 & 0.4 W/cm

• Required Mass flow = 1.2/0.7 g/s• Input fluid temperature ideally -35C• Measure room temperature operations as well

– Available enthalpy halved so mass flow needs to double– No detector current and therefore run-away less of a concern

Pixel disks Cooling pipe geometries

• 2 possible geometries

• HEX modules = 9W• Quad = 6W• Total = 9*9 + 3*6 = 99W + EOS card + Leakage current

CERN Blg158 CO2 cooling test stand(possibly a blow-off system at CERN as well)

• LHCb type Accumulator system

• PLC/SCADA control• PVSS interface

Schematic• Mass flow 0.5 to 15 g/s• Saturation temperature -27C to 25C• Input vapour quality 0.05 to 1

P-H diagram

• Pressure in 1,4,4’,5,6 defined by Acumulator

• 1 to 2 pump increases pressure, plus adds heat

• Cold liquid adjusted to required input enthalpy by heater to get to 3‘

• 3’ to 4 via needle valve• 4 to 5 boiling in stave• 5 to 6 cooling in HEX

Requirements on our side• VCR ½ inch connections• Tested to 120bar

– At start up go to almost 70Bar• Insulated

– Put in a box full of soft foam– Use the box as a transport box

• Insulated box has a relief valve > 100 mbar over pressure– Prevent CO2 pressure build up in box if stave leaks– Sized to allow CO2 out if stave ruptures without pressure build up in external box

• Leak tested to < 10-4 mbar.l.s-1

• Inlet needle valve• Temperature and pressure sensors• Power load heaters and power supplies• DAQ

Pipes that we have

• Range of pipes as staves available– S/S 3.175 mm OD; 2.775mm ID; 0.2mm wall thickness– Ti 2.275 mm OD; 2.035mm ID; 0.12mm wall thickness

• Lengths of 1.2m with and without SMC bend– Also need to add a pixel pipe

• For pipe as heater need low resistivity connection to pipe.– Copper blocks fabricated and soldered to pipe– Need to check connection fine

Using the pipe as a heaterS/S Titanium (Ti-6Al-4V)

Resistivity/ Ohm-cm 7.4e-5 4.2e-5

Outer wall diameter/ mm 3.175 2.275

Wall thickness/ mm 0.2 0.12

Resistance/ Ohm/cm 3.96e-3 5.17e-3

Module + EOS Power on stave/ W

150 150

Sensor power/ W 20 20

Total power/ W 170 170

Current/ A 13.4 11.7

Voltage/ V 12.7 14.5

Assumes a stave length of 120cmPipe heater length = 2 x stave lengthFor safety put HV in the centre of the pipe and GND at each endFor SCT cooling tests using Delta Elektronika SM- D7020-D: 35V/20A

HTC• To measure HTC need the fluid temperature and the inside pipe temperature in

heat path.• Fluid temperature = outside pipe temperature for zero heat flux; i.e. Thermally

Isolated– Measure outside pipe temperature with NTC.

• For heat load use pipe• Inside pipe temperature = Measure outside pipe temperature in heated section

and use knowledge of k_S/S or k_Ti

– Measure outside pipe temperature with NTC.• HTC f(x) => requires distributed heat load

– Add electrical connections along pipe and bridge gap with copper braid. 8cm sections and 2cm gaps.

– Power density increases a little– S/S: 15A,with ΔV= 0.5V per unit– Ti: 13A,with ΔV= 0.5V per unit

Other items• Safety values

– Still to do– Used Swagelok for C3F8/C2F6 have range to suite pressure

• DAQ– Have system for Temp/Pressure (Voltage) measurements based on Analogue

devices FPGA evaluation board with Labview software– Requires a little work to duplicate.

• Insulated box– R.F. has identified such, use as transport box

• Relief valve– Still to do

• Flow meter/Temperature sensors/Pressure sensors– Flow meter in Oxford– Temperature sensors from

Measurement matrix for stavesTmax= -35°C Mass flow [g/s]

Linear power density [W/cm] 0.7 1.2

0.8 3 1

0.7 2 1

0.6 2 2

0.5 2 3

0.4 1 3

Tmax= -30°C Mass flow [g/s]

Linear power density [W/cm]

0.7 1.2

0.8 3 2

0.7 3 2

0.6 3 3

0.5 3 3

0.4 2 3

Tmax= -25°C Mass flow [g/s]Linear power density [W/cm]

0.7 1.2

0.8 3 20.7 3 20.6 3 30.5 3 30.4 2 3

Tmin=15°C Mass flow [g/s]

Linear power density [W/cm]

1.4 2.4

0.8 3 2

0.7 3 1

0.6 3 2

0.5 2 3

0.4 1 3

L.P.D Short strips = 0.67 W/cm; Long strips =0.4 W/cm