Transcript UPGRADE ATLAS Meeting August 12, 2008 University of Santa Cruz Cooling System Work Marco Oriunno, SLAC M.Oriunno, SLAC Santa Cruz, August 12th 2008

UPGRADE
ATLAS Meeting
August 12, 2008
University of Santa Cruz
Cooling System Work
Marco Oriunno, SLAC
M.Oriunno, SLAC
Santa Cruz, August 12th 2008
Considerations I
UPGRADE
Carbon Dioxide is under consideration to replace fluorocarbon as a refrigerant fluid
for the upgrade of the ATLAS inner detector (Pixel/Strips)
Direct advantages inside the tracker volume compared to the present fluorocarbon
based system:
Lower temperatures easily achievable O(-50oC) -> high protection against
the risk of thermal runway
Higher refrigeration capability -> smaller pipes (integration/material
budget)
Reduced mass flow per refrigerated power -> pressure drops & pipe size
Compact cooling system plant
Distinctive features:
High standstill pressure (10÷60 bars)
Natural gas, not flammable, dielectric and not toxic
Negligible Global Warming Potential and Ozone Depletion Impact
Fluorocarbons will be soon banned, the refrigeration industry has started the CO2
Rush as the next refrigeration standard.
M.Oriunno, SLAC
Santa Cruz, August 12th 2008
Considerations II
UPGRADE
Although the CO2 advantages are acknowledged, there is not yet any official endorsement of CO2
cooling system for ATLAS
Several groups are already working on cooling calculations, but only few experimental installations are
available only in Europe: NIKHEF, Liverpool both with basic blown systems
CMS also has expressed interest in carbon dioxide cooling for the Tracker upgrade: CERN plans to
organize few one-day technical forums starting next October.
On the path of growing the ATLAS upgrade effort at SLAC, the involvement of SLAC in the CO2
cooling project has a two-fold advantage : it is a complement to the US ATLAS activities and encourages
the growth of user presence on the site.
To develop the possibility of a SLAC involvement took an explorative trip on week June 23-27 :
• One day meeting at NIKHEF to discuss ( with Nigel and Georg) the ATLAS cooling needs,
technical visit of the CO2 Blown system.
• Meeting with the CMS engineers involved in the CO2 upgrade to establishing communication,
plan to exchange information to solve common problems
• Technical Visit at CERN of the CO2 plant of LHCb VELO detector, running stable at -30oC
• Independent private discussions with the ATLAS colleagues based at CERN (Neal, Vic, Andrea,
Christophe) on the features of the present cooling system and various integration aspects
Attempt to take the most updated and unbiased picture of the ATLAS cooling upgrade project
M.Oriunno, SLAC
Santa Cruz, August 12th 2008
SLAC PLAN
UPGRADE
STEP 1, Development of a blown CO2 plant with small refrigeration capacity,
Unavoidable move to coalesce people and resources around the project
Characterization of the boiling parameters and the heat transfer
Pipes characterization under high pressure: materials, sizes
Thermal test of small detector prototypes from other US ATLAS group
STEP 2, development of a real vapor-compression plant with larger refrigeration
capacity, few kW : a non trivial extrapolation of the previous exercise.
Test of full scale stave/disk prototypes
Characterization of components : capillaries, heat exchangers, evaporators
Parallel activity,
Participation to the definition of specs for the upgraded cooling plant:
Thermal issues detector related : mat. budget, heat transfer, pressure drops
Plant design: choice of compressors, heaters, heat exchangers, piping, integration.
M.Oriunno, SLAC
Santa Cruz, August 12th 2008
SLAC PLAN, details(*)
UPGRADE
Start experimental Data
Today
08.12
Procurement Launch
$$$
(*) To be consolidated after real knowledge of the %effort of people involved. I counted myself at 100% which is not the case at the present
M.Oriunno, SLAC
Santa Cruz, August 12th 2008
UPGRADE
M.Oriunno, SLAC
Santa Cruz, August 12th 2008
UPGRADE
Step 1, The Blown System
The maximum refrigeration power is limited and defined by a reasonable time to swap
the CO2 cylinder: for 10 watts are needed 0.085 g/s, i.e. 80 hours continuously
Start with a dummy heater on a ¼” pipe to commission the system at few mg/s
Boiling heat transfer studies :
Several mathematical models available for different boiling regimes
Very scarce data in the open literature
Effect of evaporator shape and surface material finishing
Pressure drop studies with different evaporator shapes and sizes
Thermal test of stave module detector prototypes: thermal resistance fluid-sensor
M.Oriunno, SLAC
Santa Cruz, August 12th 2008
UPGRADE
Step 2, A medium size vapor-compression cycle
As soon as large size stave prototypes become available in the US ATLAS community, the
blown CO2 plant must be upgraded to a medium size vapor-compression plant of ~10kW
•
The design will require some time because of the several details to be proper
addresses
•
The safety and installation issues will require also more attention and time
•
The financial investment will be more important
Such architecture may well be adopted for the ATLASup ID, therefore it is worth to start to
look at general technical solutions which can be scaled up or down for both systems.
M.Oriunno, SLAC
Santa Cruz, August 12th 2008
ATLAS ID cooling plant, first thoughts
UPGRADE
We have started think about the global architecture of the final cooling system
Many options and variants are possible using CO2 :
1. Adopt the same design as for the fluorocarbon, but at least try to improve the
known weak points
2. Adopt a modified vapor-compression cycle (trans critical cycle)
3. Adopt a completely different solution, similar to the LHCb VELO, with an
Accumulator Pressure Loop
Performances and costs for all the options should be fairly compared before to make
the final choice but it could be a long process.
We need soon a document with the minimal functional requirements of the cooling
system upgrade : heat loads, temperature range, radiation environment, tracker
opening scenario, B-layer insertion, beam pipe bake out, thermal barriers and
controls.
Such document should be brief and leave out the technical solutions as much as
possible.
M.Oriunno, SLAC
Santa Cruz, August 12th 2008
ATLAS ID cooling plant, first thoughts
UPGRADE
At the present we consider the option 1, the less steep to climb because :
1. It is a well proven scheme in refrigeration industry for large installation
2. There are not practical limitations to the refrigeration power ( worth to recall that
ATLAS ID-up is close to 0.25 MW)
3. Allow naturally the reliable location of the plant in a radiation protected
environment
4. Minimize the integration space through warm transfer line
5. Long time experience and trained people in the ATLAS community
6. The factorial risk increase innovating on fluid and cooling plant architecture at the
same time, i.e. know how, people and costs.
Since we believe that a vapor-compression remains after all a good solution for the
ATLAS ID upgrade, exploring the conceptual design for such a system, not only will
provide some preliminary answers but also the guidelines for the Step 2, a medium
size vapor-compression cycle.
M.Oriunno, SLAC
Santa Cruz, August 12th 2008
INNER TRACKER
stave -25°C
capillary
UPGRADE
Heat Exchanger
gas heater
Distribution rack
Distribution rack
Pressure
regulator
Experimental cavern
BPR setpoint
P
PR setpoint
P
CO2 plant with
unchanged C3F8
architecture
Heat loads expected
Item
Power
(kW)
Pixel
10
Barrel Strips
70
Disks
50
Heat losses
20
TOTAL
150
Total with safety
factor
250
Shielded and
accesible area
condenser
Subcooling
Heaters and
Heat Exchangers
outside tracker
volume
Oil free compressor
INNER TRACKER
stave -40°C
capillary
Heat Exchanger
Distribution rack
Distribution rack
Experimental cavern
BPR setpoint
P
Pressure
regulator
P
PR setpoint
CO2 plant with
upgraded architecture
Shielded and
accesible area
condenser
M.Oriunno, SLAC
Oil free compressor
Santa Cruz, August 12th 2008
Global architecture
UPGRADE
P=10 bar
T= 20°C
H2O flow = 35 m3/h
Total thermal load 240 kW
P=10 bar
T= -40°C
Water HEX 20oC
P=10 bar
T= -40°C
F
Stav
e
83 kW
-40 oC
P=58 bar
T=20°C
E
T
Main line liquid
UX15 - Detector
60 x Ø4/6
P = 384 mbar
Water
ca
pil
lar
y
vapor quality 0.9
CO2
60 x Ø4/6
inlet distribution inside detector
P = 1bar
L
vapor quality 0.38
CoolPack
CYCLE ANALYSIS : ONE-STAGE CYCLE
> DX EVAPORATOR
PR
Ditribution rack
X4
LOG(p),h-DIAGRAM
P=10 bar
T= 20°C
QSGHX : 0 [kW]
P=10 bar
T= 20°C
Ditribution rack
X4
5
4
T2 : 192.0 [°C]
Pressure Regulator
3
T4 : 18.0 [°C]
BPR
2
QC : 384 [kW]
T5 : 18.0 [°C]
TC : 20.0 [°C]
T3 : 192.0 [°C]
SUB-DIAGRAM
WINDOWS
Back Pressure Regulator
W : 158.5 [kW]
m : 0.9817 [kg/s]
QE : 240 [kW]
6
TE : -40.0 [°C]
T7 : 20.0 [°C]
8
© 1999 - 2001
1
Main line liquid
USA15 - UX15
4 x Ø30/34
P = 150 mbar
T8 : 21.0 [°C]
T1 : 21.0 [°C]
Department of
Mechanical Engineering
Main line gas
USA15 - UX15
P = 120mbar
7
X6 : 0.42 [kg/kg]
Technical Univ ersity
of Denmark
Version 1.46
TOOL C.1
REFRIGERANT : R744
COP : 1.514
COP* : 1.521
CARNOT : 0.391
T=20°C
P=58 bar
T=18°C
P=58 bar
T=192°C
P=58 bar
T=20°C
Condenser
Pressure ratio
(P2/P1) = 5.8
B
C
LCO2
receiver
D
Water HEX 16oC
3
H2O flow = ?? m /h
P= 10 bar
T = 20oC
384 kW
A
250 Nm3/h
M.Oriunno, SLAC
6.44 m3/h
Reciprocating
Compressor 152 kW
Refrigeration Load = 250 kW
C02 mass flow = 1.3 kg/s
M.Oriunno, SLAC
July 15 2008
Santa Cruz, August 12th 2008
Estimated Performances
UPGRADE
Parameter
Refrigeration load
Evaporation temperature
CO2 mass flow
Compressor Power
Compressor Volumetric flow
Compression ratio
Compressor Max Temperature
Condensation temperature
Gas Cooling Heat rejected
Condensation Heath rejection
Sub-cooling
Super-heating
Symbol
Qe
Te
mf
Qc
Vf
R
Tm
Tc
Qg
Tl
Qu
Qb
Min
150 kW
-40oC
0.789 kg/s
91 kW
150 Nm3/h
5.8
185oC
20oC
154 kW
123 kW
16 kW
52 kW
Max
250 kW
-40oC
1.315 kg/s
152 kW
250 Nm3/h
5.8
185oC
20oC
257 kW
205 kW
27 kW
87 kW
C3F8
60 kW
-25oC
1.056 kg/s
60 kW
530 Nm3/h
6
90oC
52oC
41 kW
90 kW
35 kW
NA
Distinctive features:
Low mass flow
Low volumetric flow
None or light sub-cooling but in the
experimental cavern
Heater and/or heat exchanger outside
the cold volume
Significant increase of the condensers
capacity
Higher gas rejection temperature at the
compressors
M.Oriunno, SLAC
Santa Cruz, August 12th 2008
Capillaries
UPGRADE
Capillaries are fully passive devices and therefore are the most reliable devices to drop
pressure inside an inaccessible and harsh environment.
Length very dependent on several parameters like inlet conditions and mass flow
Preliminary simulations done by Vic Vacek, CTU Prague (private communication) confirm
that the final capillary length for CO2 is not so different form C3F8 ~2-3 meters
V.Vacek
Parameters of adiabatic capillary flow:
Inlet pressure of sub cooled liquid … pin = 58 bar
Inlet temperature of sub cooled liquid … Tin = 18°C
Capillary tube inner diameter … ID = 0.60 mm and 0.80 mm
Relative inner wall roughness: ε ID = 0.003
ID=0.6 mm
V.Vacek
ID=0.8 mm
V.Vacek
M.Oriunno, SLAC
Santa Cruz, August 12th 2008
High Pressure and piping
UPGRADE
The high standstill pressure of the CO2 (~60 bar) is generally raising questions and
concerns about the size and the reliability of pipes and connectors
One should note that high pressure piping with ~ 150 bars and beyond, are routinely
handled in large chemical process plants with a satisfying level of reliability and safety
Of course this should not relax the effort of to design the pipe work in very detail,
especially of the part inside the cold volume, which will not be anymore accessible after
the sealing and the irradiation
Pressurized piping must be compliant with the code ASME B31.3 where the material
grades, the minimum wall thickness and the allowable stresses are given as function of
pipe diameter and the design gage pressure. For straight pipe under internal pressure the
minimum wall thickness is given by:
Pd
t
2( SEW  P(1  Y )
Where d is the inner diameter, P the design pressure, S the allowable stress, Y, E and W are coefficients depending on
the quality of the material. The following figures show the size of the pipes for the two cases of high pressure (60 bar)
and low pressure (10 bar) :
0.6
0.05
Al
0.04
0.4
t ( di Sss)
Copper
t ( di Scu)
Material
Stainless Steel
Copper
Aluminum Alloy
Xo
(cm)
1.76
1.35
8.9
Min wall thickness mm
(ASME B31)
0.10
0.19
0.30
Radiation length/Xo
t ( di Sss)
t ( di Sal)
0.02
1.13 %
2.81 %
0.67 %
0.2
Copper
Steel
Steel
0
0
0
3
3
4
5
di
6
6
High Pressure 60 bar for Stainless steel, Copper and Aluminium
M.Oriunno, SLAC
Al
t ( di Scu)
t ( di Sal)
0
12
12
14
16
di
18
20
20
Low Pressure 10 bar for Stainless steel, Copper and Aluminium
Santa Cruz, August 12th 2008
Pressure drops calculations
UPGRADE
We can adopt for CO2 the same distribution used for the C3F8.
The Inner detector is subdivide in four quadrant fed independently by a 30/34 mm liquid
line and a 72/76 mm vapor line.
Distribution racks fan in to ~ 50 liquid lines 4/6 mm and fan out 18/20 mm vapor
lines.
The racks contain also the pressure and the back pressure regulators valve which set,
independently for each channel, the mass flow and the evaporation temperature
pressure drops
Compressor to Racks
Racks to Inner Detector
Internal piping Inner detetctor
Inner Detector to racks
Racks to Compressor
M.Oriunno, SLAC
Phase
liquid
liquid
liquid/vapor
vapor
vapor
# channels
4
200
200
200
4
Mass flow per channel (g/s)
250
5
5
5
250
Max Length (m)
177
25
~
25
177
Pipe ID (mm)
30
4
~
18
72
Pressure drop (mbar)
220
534
8
91
Santa Cruz, August 12th 2008
Conclusions
UPGRADE
Plan to develop at SLAC an US ATLAS CO2 cooling facility
Blown CO2 system in construction -> expected to run end of September
Larger plant in design phase, main components have been sized
Preliminary calculations shows that for the final ATALSup ID, adopting CO2 in a
vapor-compression cycle similar to the present plant running with C3F8, is feasible
and offers many advantages due to the better physical properties of CO2.
It provide also enough margin to eliminate the weak points shown so far by the
present C3F8 system
It fit well in super high irradiated environment like SLHC
It minimize the unavoidable take of risk stemming from the adoption of too many
technological unknowns.
M.Oriunno, SLAC
Santa Cruz, August 12th 2008