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 1/12 th – 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 V i Vapour quality at output = 0.5 Enthalpy = 310J/g (at -35C) Power = 170/100W (short and long stave) & ~100W for 1/12 th 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 < 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 mm OD; 2.775mm ID; 0.2mm wall thickness – Ti 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 heater S/STitanium (Ti-6Al-4V) Resistivity/ Ohm-cm7.4e-54.2e-5 Outer wall diameter/ mm Wall thickness/ mm Resistance/ Ohm/cm3.96e-35.17e-3 Module + EOS Power on stave/ W 150 Sensor power/ W20 Total power/ W170 Current/ A Voltage/ V Assumes a stave length of 120cm Pipe heater length = 2 x stave length For safety put HV in the centre of the pipe and GND at each end For 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 staves Tmax= -35°C Mass flow [g/s] Linear power density [W/cm] Tmax= -30°C Mass flow [g/s] Linear power density [W/cm] Tmax= -25°C Mass flow [g/s] Linear power density [W/cm] Tmin=15°C Mass flow [g/s] Linear power density [W/cm] L.P.D Short strips = 0.67 W/cm; Long strips =0.4 W/cm