LHCb-VELO Microchannel fracture safety system and evaporator concept 26 June 2015 Bart Verlaat 1.
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Transcript of LHCb-VELO Microchannel fracture safety system and evaporator concept 26 June 2015 Bart Verlaat 1.
LHCb-VELO Microchannel fracture
safety system and evaporator concept
26 June 2015
Bart Verlaat 1
Microchannel volume (1)
• The minimum volume which we can shut-off is 1 u-channel including the in and outlet pipes.
• The worst case is a filling of cold liquid – T-30ºC liquid (1076 kg/m3)
used in analyses– Under normal circumstances
vapor is present and less CO2 is present.
• Assuming a 0.5mm inlet and 1.2mm outlet (1m long)– See quick CoBra analyses 2
0 0.5 1 1.5 2-35
-30
-25
-20
-15
Velo Upgrade thermal profileMF=0.3 g/s, Tsp=-25ºC, Q
app=40 W, Q
env=0 W, x
end=0.45 dP=4.62 bar
Branch length (m)
Tem
pera
ture
(ºC
)
1 23 4 5
1x, D
=0.5
mm
19x,
D=0
.06m
m
19x,
D=0
.15m
m
1x, D
=1.2
mm
¯T
ur R
e=50
21
v
=1.4
5 m
/s
¯T
ur R
e=50
22
v
=1.4
5 m
/s
¯T
ur R
e=50
23
v
=1.4
5 m
/s
¯T
ur R
e=50
24
v
=1.4
5 m
/s
¯A
nnu
x=0
.18
¯A
nnu
x=0
.45
¯A
nnu
x=0
.45
¯A
nnu
x=0
.45
¯A
nnu
x=0
.45
¯A
nnu
x=0
.45
0
10
20
30
40
Pre
ssur
e(B
ar)
T Structure
T Tube wall (ºC)
Tsat Fluid (ºC)T Fluid (ºC)
P Fluid (Bar)
Microchannel volume (2)
• Module volumes and CO2 content @ -30ºC liquid (1076 kg/m3):– Inlet: D0.5mm x 1m = 0.2 ml
• 0.21 gram
– μ-channel: 19x (60μm* 60μm*30mm+120μm*200μm*267mm) = 0.12 ml• 0.13 gram
– Outlet: D1.2mm x 1m = 1.1 ml• 1.2 gram
– Total module volume: • 1.6 gram CO2 total
• Vacuum volumes (Eddy Jans memo, 5 November 2009) :– Secondary: 450 liter– Primary: 1715 liter– Maximum dP=10 mbar
• Loosing 1.6 gram of CO2 in the secondary volume gives a density of 1.6 g / 450 l = 3.5 g/m3– 3.5 g/m3 density after warming up to 20’C gives a pressure of 1.9mbar– Direct expansion without heat pick-up is
• Conclusion: 1 μ-channel leak is not critical! But a proper module shut-off mechanism is needed
3
Venting CO2 in vacuum
4
3.5 g/m3 => v=285 m3/kg
Far off scale
Ca 350 kJ/kg*1.6 g = 560 J to heat it up to ambient.
Condition of -30 C liquid ⁰
Condition of +20 C ⁰low pressure gas
How can we isolate 1 μ-channel?
• 3 module shut-off options:
– Place no-return valves at each module inlet and outlet• Will add the inlet manifold volume to the leaking volume• 1 critical active common inlet valve• No risk of liquid trapping• Need a reliable miniature no return valve
– Place a shut-off valve at the inlet and protect the outlet return flow with a no-return valve
• No risk of liquid trapping• Need a reliable miniature no return valve• Many active valves in the vacuum
– Place shut-off valves at each module inlet and outlet• Risk of liquid trap• Many active valves in the vacuum• For safe operation:
– A relieve: risk of leak or an atmospheric back flow.– A safety gas volume: need a small heat source to keep it filled with gas (might be ambient) 5
No return valve option
• This concept requires small passive no return valves.• Actuator can be out of the tertiary vacuum • Inlet manifold will be leaked into the vacuum as well:
– Assuming a 4x0.7 tube & 1m long– Extra Volume: 5.3 ml = 5.7 gram– Pressure in secondary vacuum @ 20’C = 8.9 mbar 6
1 Active NC valve needed and many miniature no return valves
Red volume will leak in vacuum
Green volume can stay pressurized. An additional pressure relieve can be included
Ambient Tertiary vacuum Secondary Vacuum
Valve is NC and actuated when a pressure increase in the Velo is detected. Eg. 1e-3mbar
Individual inlet shut-off
• This concept requires small passive no return valves.• 26 actuators in the tertiary vacuum
– Pneumatic valves very complex in a vacuum– Electrical valves NC have a constant heat load on the
CO2 inlet• Small volume leaked into vacuum
– Pressure in secondary vacuum @ 20’C = 1.9 mbar7
26 Active NC valves needed in vacuum and 26 miniature no return valves
Red volume will leak in vacuum
Green volume can stay pressurized. An additional pressure relieve can be included
Ambient Tertiary vacuum Secondary Vacuum
Valves are NC and actuated when a pressure increase in the Velo is detected. Eg. 1e-3mbar
Full active shut-off
• This concept is very sensitive for trapping cold liquid– Each line needs a relieve mechanism– Open relieve mechanisms (Burst disc or safety valves) are a risk for the modules
(sudden cool down when activated)– A warm safety volume is an option
• 52 Actuators in the tertiary vacuum– Pneumatic valves very complex in a vacuum– Electrical valves NC have a constant heat load on the CO2 inlet
• Small volume leaked into vacuum– Pressure in secondary vacuum @ 20’C = 1.9 mbar
8
52 Active NC valves needed in vacuum
Red volume will leak in vacuum
Green volume can stay pressurized. An additional pressure relieve can be included
Ambient Tertiary vacuum Secondary Vacuum
Valves are NC and actuated when a pressure increase in the Velo is detected. Eg. 1e-3mbar
Safety volume always contains warm gas
All
Upgrade Velo cooling vs current Velo cooling
9
All inlet capillaries on 1 side. Return common (Manifold inside)
Electronics crates
Cable feedthrough
Tertiary vacuum with manifolds and safety valves
Cooling feed through with thermal stand-off
Out of the way space for cooling connector and flexible part
Cooling lines passing the module base on the side
Safety system continued
• The all no-return valve option seems optional and favorable (option 1)– Simplest from control point of view
• No active parts in vacuum
– Need to develop a reliable miniature no-return valve• A small leak rate still tolerable as the vacuum
pump continues pumping (Ca. 10 mg/s allowed)
• Other options require many active valves (26 or 52) all in vacuum.
10
CO2 pumping in secondary vacuum
11
10-2
10-1
100
101
102
103
10-4
10-3
10-2
10-1
100
101
Pressure (mbar)
Mas
sflo
w (
g/s)
ACP28 CO2 pumping capacity
Pressure (mbar)
Mas
s flo
w (
g/s
)
ACP 28 pumping capacity for CO2
A constant CO2 leak of 10 mg/s is tolerable
At least 1 ACP28 pump is active, sometimes 2 work in parallel
Concept Evaporator P&ID
12
PV110
nc
TT35036
To UT-Detector
30
30
60
52
EH39052TT39052
CV39052 EH30036 CV30038 PV30038
NV30142
NV30148
NV30242
NV30248
NV30342
NV30348
nc
nc
EH35036 CV35038 PV35038
NV35142
NV35148
NV35242
NV35248
NV35342
NV35348
PV35052
nc
PV35040
nc
PV35050nc
PV39060
nc
PV39030
nc
PV30040
nc
PV30050
PV59032PV59054
PV49060
PV49030
nc
nc nc
36
PT35052TT35052BD35052
52
PT35038TT35038
38
SA35052
SA30052
PT30038TT30038
38
Safety vent
By-pass with dummy load
Pre-heater
Safety vent
Pre-heater
nc
PV35052
52
PT30052TT30052BD30052
TT39032PT39032BD39032
32
TT30036
36
60
PT39058TT39058BD39058
58
VacuumAmbient
P&ID explained
• Labelling (QQxyyzz)– QQ=component
• PV=Pressure valve• CV=Control Valve• NV=No Return Valve• TT=Temperature transmitter• PT=Pressure Transmitter• EH=Electrical Heater• SA=Safety Accumulator
– x=System ID• 1=Chiller A• 2=Chiller B• 3=CO2 Velo • 4=CO2 UT• 4=CO2 Common• 6=Dry-air• 7=Tertiary Vacuum
– yy=Branch ID• 00 = Aside common• 01…26 = Evaporator 1 to 26, A side• 50 = C –side common• 51-76 = Evaporator 1 to 26, C side• 90 = General (Inlet, By-pass & return)
•
• UT and Velo can be connected at the level of the accumulator
– PV59054 & PV59032 open– Close the PV39030 & PV39058 incase of Velo failure or visa
versa
• Preheater EH30036 & EH35036 regulate TT30036 & TT35036
• The Pressure difference (PT39032-PT39058) is regulated constant with CV39052
– CV30038 & CV35038 are set constant for a certain evaporator flow
– The constant dP allow the sharing of the UT
• Safety procedure– If Pvacuum>10-3 mbar, then close PV30038, PV35038, PV30052 & ,
PV35052 – If PT30038 < PT39058 – 3bar, then open PV30040 & PV30050;
This means there is a leak in this section– If PT35038 < PT39058 – 3bar, then open PV35040 & PV35050;
This means there is a leak in this section– System remains running over by-pass, to stay active for safety
control and UT operation– The safety procedure is safe by default valve position (No
venting), Venting is done in addition to be more safe. A safe vent action requires NO valves, but than there is a high risk of unwanted venting which is a hazard for the modules as a cool down is a result.
• A safety accumulator in the module section must prevent accidental liquid trap. The SA has always a gas filling. 13