1. Centre de Physique des Particules de Marseille
Saturated CnF(2n+2) Fluorocarbons and their blends
in the context of on-detector cooling channels the ATLAS High Luminosity Tracker Upgrade
G. Hallewell
Centre de Physique des Particules de Marseille
Representing the work of a lot of people engaged in FC blends and sonar studies…
G. Hallewell: ATLAS tracker upgrade on-detector cooling meeting, CERN , May 31, 2012

2. Principal advantage… lower evaporating pressure
Why study saturated CnF(2n+2) fluorocarbons
in the on detector cooling channels of upgrade?
Principal advantage… lower evaporating pressure
A back up solution which would allow reuse of existing
(un-insulated) liquid supply & vapour return tubing through
muon chambers and external tubing, including thermosiphon;
Unnecessary to dismantle part of the muon spectrometer to
de-install existing tubing services and install new ones;
Possible saving of man hours of labour in a future
Environment that might be financially uncertain
Compatible with thermodynamics of thermosiphon
presently (and visibly) under construction  
G. Hallewell: ATLAS tracker upgrade on-detector cooling meeting, CERN , May 31, 2012

3. ATLAS FC Thermosiphon external surface status, May 25, 2012
G. Hallewell: ATLAS tracker upgrade on-detector cooling meeting, CERN , May 31, 2012C

4. C3F8/C2F6 blend comparison summary with CO2
Coolant
PEvap(bar abs)
Dp L-V - 50°C
P Evap(bar abs)
Dp L-V - 40°C
Dp L-V - 30°C
CO2
6.8
10.0
14.3
C3F8
0,53
0,87
1,36
80%C3F8/20%C2F6
1,50-0,70
2,21-1,14
3,16-1,78
50%C3F8/50%C2F6
2,36 - 1,07
3,59 - 1,82 5,
20%C3F8/80%C2F6
3,22-2,17
4,70-3,36
6,63-5,00
C2F6
3.7
5.4
7.6
G. Hallewell: ATLAS tracker upgrade workshop, Oxford, March 28-April 1, 2011

5. BACKGROUND TO BLEND-MAKING (A common technique)
Present (urgent) requirement for C2F6/C3F8 blends is for SCT
(can’t meet TDR Si temp spec. Excessive DP in exhaust Hexs & heaters)
 add more volatile C2F6 to C3F8 raises evaporation pressure at same operating temperature, to overcome pressure drops in exhaust Hexs & heaters
10% C2F6
in C3F8
20% C2F6
in C3F8
30% C2F6
in C3F8
Pevap(max)= 3.6bara
For Tevap ~ -25°C
Pevap(max)= 4.4bara
For Tevap ~ -25°C
Pevap(max)= 2.8bara
For Tevap ~ -25°C
G. Hallewell: ATLAS tracker upgrade workshop, Oxford, March 28-April 1, 2011

6. in SCT barrel thermal test structures
We have built a blend circulator and have been been studying cooling with C2F6 /C3F8 blends
in SCT barrel thermal test structures
G. Hallewell: ATLAS tracker upgrade on-detector cooling meeting, CERN , May 31, 2012

7. Fluorocarbon blend circulator UNICOS representation
G. Hallewell: ATLAS tracker upgrade on-detector cooling meeting, CERN , May 31, 2012

8. un-precooled tubes to thermal test stand at other end of SR1
Unlike present ID evaporative cooling system, compressor has a single stage (9 bar output): a liquid booster pump is needed (height limit -2m) to send liquid through 50m
un-precooled tubes to thermal test stand at other end of SR1
G. Hallewell: ATLAS tracker upgrade on-detector cooling meeting, CERN , May 31, 2012

9. Example of P-h diagram for blend circulator (using present SCT “internals” and operating with C3F8
Op. Point
P (barabs )
Temp (°C)
Physical State and location A
1.7
-25
Saturated vapour at the output of the SCT thermal test structure B
0.8 20
Superheated vapour at the input to the compressor C
9.0 50
Superheated vapour at the output of the compressor D 25
Saturated liquid at the exit of the condenser E 12 15
Pressurised and pre-cooled liquid at liquid pump output F 13
18-20
Pressurised liquid at the output of the 50m tubing linking the blend machine to the thermal test stand G
Pressurised and sub-cooled liquid at the capillary input H
Saturated liquid at the output of the capillary and entrance to the SCT thermal test structure
G. Hallewell: ATLAS tracker upgrade on-detector cooling meeting, CERN , May 31, 2012

10. Example of P-h diagram for blend circulator (using present SCT “internals” operating with 25%C3F8/75%C3F8
Op.
point P
(barabs )
Temp (°C)
Physical State and location A
2.1
-25
Saturated vapour at the output of the SCT thermal test structure B
0.8 20
Superheated vapour at the input to the compressor C
9.0 50
Superheated vapour at the output of the compressor D 25
Saturated liquid at the exit of the condenser E 12 15
Pressurised and pre-cooled liquid at liquid pump output F 13
18-20
Pressurised liquid at the output of the 60m tubing linking the blend machine to the thermal test stand G
Pressurised and sub-cooled liquid at the capillary input H
2.8
Saturated liquid at the output of the capillary and entrance to the SCT thermal test structure
G. Hallewell: ATLAS tracker upgrade on-detector cooling meeting, CERN , May 31, 2012

11. back pressure measured immediately upstream of BPR)
Reduction in maximum tube temperature vs C2F6 concentration in C3F8 (evaporation pressure = 2.2 bar abs)
back pressure measured immediately upstream of BPR)
Preliminary data from Alex Bitadze: May 2012
G. Hallewell: ATLAS tracker upgrade on-detector cooling meeting, CERN , May 31, 2012

12. Difference in Maximum Temperature over the SCT Barrel stave,
in case of 13barabs inlet (pre-capillary) pressure and different
back pressure in system.
Preliminary data from Alex Bitadze: May 2012
G. Hallewell: ATLAS tracker upgrade on-detector cooling meeting, CERN , May 31, 2012

13. SR1: Barrel SCT test structure: flowmetry & blend analysis in the exhaust
G. Hallewell: ATLAS tracker upgrade on-detector cooling meeting, CERN , May 31, 2012

14. Combined ultrasonic flowmeter and C2F6 / C2F6 mixture analyzer
G. Hallewell: ATLAS tracker upgrade on-detector cooling meeting, CERN , May 31, 2012

15. Sound velocity vs. C2F6 molar conc. in C3F8: instrument precision ~ 0
G. Hallewell: ATLAS tracker upgrade on-detector cooling meeting, CERN , May 31, 2012

16. Note: this set up doesn’t measure and has glued-together tubes.
SR1: Barrel SCT test structure: 2+2 staves, 48 modules: 2 capillaries, 1 shared exhaust
Note: this set up doesn’t measure
HTC (or CCHT?): it doesn’t have temperature sensors on heated dummy module locations,
and has glued-together tubes.
G. Hallewell: ATLAS tracker upgrade on-detector cooling meeting, CERN , May 31, 2012

17. SCT Barrel Cooling Loop (stave)
48 dummy heaters (ceramic plate with resistive trace on the top surface) are installed in place of the silicon modules.
The cooling loop was instrumented with NTC thermistors along its length and with pressure sensors at the start, middle and end of the loop.
G. Hallewell: ATLAS tracker upgrade on-detector cooling meeting, CERN , May 31, 2012

18. General View of cooling test stand in SR1
G. Hallewell: ATLAS tracker upgrade on-detector cooling meeting, CERN , May 31, 2012

19. G. Hallewell: ATLAS tracker upgrade on-detector cooling meeting, CERN , May 31, 2012

20. P_BH
P_AH
Heater with Pressure sensors P_BH and P_AH.
(orientation of the heater as in ATLAS)
Coiled Cu pipe (14mm ID, 30m) to reproduce the return line in the ATLAS experiment.
G. Hallewell: ATLAS tracker upgrade on-detector cooling meeting, CERN , May 31, 2012

21. Back pressure regulation
(BPR, Pressure sensors: P_BBPR, P_BFM, By-pass) and Bronkhurst flow meter.
By-pass
P_BFM
Dome P.
BPR
P_BBPR
Control of the back pressure regulation
(N2 bottle with manual pressure regulator to control dome pressure).
“Bronkhorst” flow meter.
Model: F-113AC-AAD-99-V
G. Hallewell: ATLAS tracker upgrade on-detector cooling meeting, CERN , May 31, 2012

22. TOOLS to USE (thanks to Georg for FLUDY)
E. Lemmon, M. Huber & M. McLinden,
‘REFPROP’ Standard reference database
23, version 9.0
U.S. Nat. Inst. Stand. & Technology (2010)
E. Lemmon & R. Span
“Short fundamental equations of state
for 20 fluids”,
J Chem. Eng. Data 51 (2006)
G. Hallewell: ATLAS tracker upgrade on-detector cooling meeting, CERN , May 31, 2012

23. What reference was used to arrive at these conclusions?
G. Hallewell: ATLAS tracker upgrade on-detector cooling meeting, CERN , May 31, 2012

24. 80% C3F8/20% C2F6 pressure - enthalpy
Evaporation, condensation no longer isobaric
(in common with many CFC-replacement blends):
Pevap (-40°C) ~ 2.211.14 barabs
G. Hallewell: ATLAS tracker upgrade on-detector cooling meeting, CERN , May 31, 2012

25. 50% C3F8/50% C2F6 pressure - enthalpy
Evaporation, condensation no longer isobaric
(in common with many CFC-replacement blends):
Pevap (-40°C) ~ 3.591.82 barabs
G. Hallewell: ATLAS tracker upgrade on-detector cooling meeting, CERN , May 31, 2012

26. 20% C3F8/80% C2F6 pressure - enthalpy
Evaporation, condensation no longer isobaric
(in common with many CFC-replacement blends):
Pevap (-40°C) ~ 4.703.36 barabs
G. Hallewell: ATLAS tracker upgrade on-detector cooling meeting, CERN , May 31, 2012

27. Back to the future?
HTC measurements in C3F8/C4F10 blends (Average over 1.6m length, 12 stations) ( ) Name (& politics) of the (then) game – progressive C3F8 acceptance: choose evaporation pressure as close as poss. to 1 barabs Could HTC be correlated with evaporation pressure gradient?
G. Hallewell: ATLAS tracker upgrade on-detector cooling meeting, CERN , May 31, 2012

28. Pure C3F8: Pevap = 2.5barabs @ -15°C
G. Hallewell: ATLAS tracker upgrade on-detector cooling meeting, CERN , May 31, 2012

29. 20% C4F10:80%C3F8 Pevap = 2.11.7barabs @ -15°C
G. Hallewell: ATLAS tracker upgrade on-detector cooling meeting, CERN , May 31, 2012

30. Bigger Dp at 50/50 than at other
50% C4F10:50%C3F8 Pevap = -15°C
Bigger Dp at 50/50 than at other
two mixtures
G. Hallewell: ATLAS tracker upgrade on-detector cooling meeting, CERN , May 31, 2012

31. 70% C4F10:30%C3F8 Pevap = 1.30.8barabs @ -15°C
G. Hallewell: ATLAS tracker upgrade on-detector cooling meeting, CERN , May 31, 2012

32. Pure C4F10: Pevap = 0.6barabs @ -15°C
G. Hallewell: ATLAS tracker upgrade on-detector cooling meeting, CERN , May 31, 2012

33. to simulate SCT stave (DH=3.6mm, L = 1.60 m)
Measurements made in stucture: 12 * 5cm Cu blocks silver soldered on 4mm (OD) Cu tube
to simulate SCT stave (DH=3.6mm, L = 1.60 m)
-15°C
-25°C
G. Hallewell: ATLAS tracker upgrade on-detector cooling meeting, CERN , May 31, 2012

34. to simulate SCT stave (DH=3.6mm, L = 1.60 m)
Measurements made in stucture: 12 * 5cm Cu blocks silver soldered on 4mm (OD) Cu tube
to simulate SCT stave (DH=3.6mm, L = 1.60 m)
2.46 barabs
0.58 barabs
1.8 – 1.0 barabs
2.1– 1.8 barabs
barabs
C3F8 concentration in C4F10
G. Hallewell: ATLAS tracker upgrade on-detector cooling meeting, CERN , May 31, 2012

35. The pressure dependence of HTC is not very convincing!
Possibly due to the liquid overdrive used..?
Fluid set
Boiling pressure
-15°C
Approx
HTC (±~12%)
C4F10
580 mbarabs
3047
70%C4F10: 30%C3F8
0.90.48barabs
2200
50%C4F10 : 50%C3F8
1.81.0barabs
2350
20%C4F10 : 80%C3F8
2.11.7barabs
2600
C3F8
2.5 barabs
4284
G. Hallewell: ATLAS tracker upgrade on-detector cooling meeting, CERN , May 31, 2012

36. Started to look at HTC models: start “simple”:
first for pure C3F8 in ATLAS SCT tube geometry (1)
This figure for pure 4gm/sec, 4.17mm DH tube
1.7barabs evap pres. (-25°C) xin = 0.3 (30% vap), xout= 0.9 (90%vap)
G. Hallewell: ATLAS tracker upgrade on-detector cooling meeting, CERN , May 31, 2012

37. Started to look at HTC models: start “simple”:
first for pure C3F8 in ATLAS SCT tube geometry (2)
Horribly unphysical
Found Pcrit value error:
prediction more like
This figure for pure 4gm/sec, 4.17mm DH tube
1.7barabs evap pres. (-25°C) xin = 0.3 (30% vap), xout= 0.9 (90%vap)
G. Hallewell: ATLAS tracker upgrade on-detector cooling meeting, CERN , May 31, 2012

38. Started to look at HTC models: start “simple”:
first for pure C3F8 in ATLAS SCT tube geometry (3)
Liq phase therm cond.
In the model, Reynolds and Prandtl numbers not assumed to change along the stave.
Liq phase dens
Vap.phase dens.
Shah model is the most rapidly testable in terms of “x slicing” from capillary through to run out at end of stave...
This figure for pure 4gm/sec, 4.17mm DH tube
1.7barabs evap pres. (-25°C) xin = 0.3 (30% vap), xout= 0.9 (90%vap)
G. Hallewell: ATLAS tracker upgrade on-detector cooling meeting, CERN , May 31, 2012

39. ‘coefficient of convective heat transfer’...
HTC or more properly (it seems...)
This model suggests CCHT increases with vapour fraction,
whereas there is less liquid to evaporate.
So what do we MEASURE? – a liquid or vapour effect?
We don’t see such a dramatic x dependence in temperature
profile for pure C3F8 measurements...
‘x’ or ‘vapour quality’:
0 means 100% liquid,100% means 100% vapour
G. Hallewell: ATLAS tracker upgrade on-detector cooling meeting, CERN , May 31, 2012

40. Pierre (3019), Shah (2972 av.) and Slipcevic (2000) models give predictions in pure C3F8 varying by >50%!
Nevertheless, each model might be able to give some RELATIVE predictions along bi-stave with increasing vapour content etc (started for Shah model).
The three models coded in an Excel spreadsheet to adapt to any tube geometry:
Pcrit, liquid, vapour phase densities, viscosities etc. can be calculated in NIST Refprop as inputs to models
G. Hallewell: ATLAS tracker upgrade on-detector cooling meeting, CERN , May 31, 2012

41. Toward future HTC measurements in C3F8/C2F6 blends:
Toward future HTC measurements in C3F8/C2F6 blends: HTC correlated with varying internal evaporation pressure?
G. Hallewell: ATLAS tracker upgrade on-detector cooling meeting, CERN , May 31, 2012

42. A point to note: the p-h point on the saturated vapour line
Adding more volatile C2F6 to C3F8 raises evaporation pressure at the same operating temperature, or reduces the operating temperature for the same evaporating pressure
10% C2F6
in C3F8
20% C2F6
in C3F8
30% C2F6
in C3F8
PevapLiq(Vap)= 4.1(2.3)bara
For Tevap ~ -25°C
PevapLiq(Vap)= 3.3(2.1)bara
For Tevap ~ -25°C
PevapLiq(Vap)= 2.8 (1.8)bara
For Tevap ~ -25°C
A point to note: the p-h point on the saturated vapour line
is ‘downstream’ of the active cooling, in an exhaust heater
that vaporises any unevaporated liquid
Source: NIST REFPROP SRD23 v9.0 (2010): modified Benedict Web Rubin E.O.S..
G. Hallewell: ATLAS tracker upgrade on-detector cooling meeting, CERN , May 31, 2012

43. NIST Refprop Data used in Shah model by FC type: (mainly S.I. Units)
Fluid
Evap
Temp (C)
Liquid
Phase
Press
(Pa)
Vapour
Dens
(kg/m^3)
Enthalpy
(J/kg)
Vapor
Vap-Liq
Diff Cp
(J/kg/K)
Therm
Cond
(W/m.K)
(mW/mK)
Visc
(Pa.s)
Surface
Tens (mN/mm)
Vapour Phase
C3F8
-25
167710
1564,3
16,519
174060
274730
100670
1002,7
757,5
0,059597
8,9594
0,000360 0,
9,1444
20%C2F6/
80%C3F8
333850
204630
1523,8
19,135
173580
272340
98760
1017,4
752,32
0,057972
9,1775
0,000308 0,
8,367
8,9964
C2F6
896550
1329,0
75,971
169170
256570
87400
1144,8
847,78
0,054881
10,805
0,000176 0,
4,2169
We will see that entering the blend parameters above into the Shah model gives similar HTC vs.
X development as in pure C3F8
(explicit x dependence, but no pressure dependence in model)
G. Hallewell: ATLAS tracker upgrade on-detector cooling meeting, CERN , May 31, 2012

44. Shah model HTC for 20%C2F6/80%C3F8
G. Hallewell: ATLAS tracker upgrade on-detector cooling meeting, CERN , May 31, 2012

45. Relating quality factor (hypotenuse) to Pressure (Pa: ordinate) and enthalpy (J/kg: abscissa)
Note: x is measured along hypoteneuse : need correction
slope = ( )/( )= ; arctan = 52.6°
sin 52.6° = 0,794  dP/P= (dx/x)*0,794 ; cos 52.6° = 0,607  dh/h= (dx/x)*0,607
x, P & h are full scale ranges of quality (1), enthalpy ( ) & press ) respectively
Note: in Shah model h & P not explicitly used: only x
Question is whether we can use density variation with x.
G. Hallewell: ATLAS tracker upgrade on-detector cooling meeting, CERN , May 31, 2012

46. Back to the Pierre model; this time for the 20%C2F6/80%C3F8 blend
Enthalpy chopped into bites
Corresoinding to 0.1 increments in x (vap. %)
G. Hallewell: ATLAS tracker upgrade on-detector cooling meeting, CERN , May 31, 2012

47. HTC from the Pierre model; this time for the 20%C2F6/80%C3F8 blend
No x-dependence predicted
by Pierre model for blend
coefficient of convective heat transfer’...
HTC or more properly ‘
‘x’ or ‘vapour quality’:
0 means 100% liquid,100% means 100% vapour
G. Hallewell: ATLAS tracker upgrade on-detector cooling meeting, CERN , May 31, 2012

48. Pre-conclusion: “Some they do and some they don’t and some you just can’t tell…”
Some models predict HTC change with vapour quality Others don’t… and some are horribly unphysical How much effort top put in to finding an adapted model..? Georg has given us FLUDY to aid the study: BUT… General comment: HTC is less important than dynamically induced DT on tubes
G. Hallewell: ATLAS tracker upgrade on-detector cooling meeting, CERN , May 31, 2012

49. Where we are…
In SR1we have set up an operational blend machine and sonar
vapour analyzers for verifying C3F8/C2F6 blend molar ratio;
The blend machine is fully integrated into the CERN UNICOS framework,
just like other cooling plants...
Studies have been mainly oriented toward barrel SCT operation
in the present tracker –
(aimed at overcoming exhaust pressure drops expected in pure
C3F8 for Si with high radiation-induced leakage currents.)
Alex Bitadze has been the principal player (PhD thesis).
His work is now completed and he is moving into other areas.
Other CERN-based manpower is needed for investigations of reduced diameter tubes (cf. present tracker) in this ATLAS facility.
G. Hallewell: ATLAS tracker upgrade on-detector cooling meeting, CERN , May 31, 2012

50. Our priority has had to be the present detector
Extra manpower will mean that HTC, dynamic DP
measurements would be soon possible (e.g. electric current
through tube/ resistive heaters on silver soldered blocks)
in various tube diameters –
FLUDY, Shah predictions can help in diameter choice?
If these tests show that FC blends can achieve the required
evaporation temperature, at required power...
will the community accept on-detector cooling tube diameters that
would work with CO2 AND a FC blend back-up?
OTHER PARALLEL COMPARATIVE STUDY OF %X0,
LOOKING AT TRADEOFF BETWEEN %X0 IN TUBE DIAMETER,
WALL MATERIAL AND DIFFERENT THERMAL DRAINS IS NEEDED.
IMPACT PARAMETER RESOLUTION
G. Hallewell: ATLAS tracker upgrade on-detector cooling meeting, CERN , May 31, 2012

51. Unreliable exhaust heaters (moved to more accessible locations in 2007/8) would be replaced by C6F14 liquid multi-channel Hex’s
(DATE SA, Grenoble being contacted (fabricant of thermosiphon condenser))
G. Hallewell: ATLAS tracker upgrade on-detector cooling meeting, CERN , May 31, 2012

52. Rappel: there has been no review to establish a baseline coolant for the tracker upgrade
Tempting to kick the ball into the long grass - philosophy
“if we don't put effort into considering and testing FC blend
backups alternatives, the cooling will have to be CO2”
But risk a train wreck in the future if muon chambers can’t
be removed and willpower/manpower/money can’t be found for
the present C3F8 copper cooling tube strip-out and replacement;
Rappel: there has been no review to establish a baseline and
back up coolant yet...
THERE WERE TWO COOLING REVIEWS TO CHANGE
FROM TO ESTABLISH FC BASELINE (1997/8)
G. Hallewell: ATLAS track/8er upgrade on-detector cooling meeting, CERN , May 31, 2012