04/18/23 Auke-Pieter Colijn 2
Two-stage cooling
• Standard cooling– C3F8 coolant only
• Dual-system @ NIKHEF:– R404A primary coolant– C3F8 secondary coolant
• Cheap & easy ……..– Do not need oil-less compressor
04/18/23 Auke-Pieter Colijn 5
R404A
H2O condenser
Compressor
Main evaporator
Pressure control
Expansion valves
Sub-cooler
Hot gas bypass
T sensor
T sensor
1) Regulate C3F8 T with R404A evaporator P
2) Expansion valves regulate P [0-3kW@-25C]
3) Explain sub-cooler in a bit
04/18/23 Auke-Pieter Colijn 6
Primary cooling: R404A
GASGAS+LIQUID
LIQUID
A
BC
D
A-B: Compress R404A
B-C: Liquefy hot gas in H2O condenser C-D: R404A expansion
D-A: Evaporate R404A. Heat is absorbed from C3F8P
[bar
]
Enthalpy [J/g] 1.dH = dQ2. P = flow*dH
04/18/23 Auke-Pieter Colijn 7
C3F8 system for Testbox
Pump
10-12 bar P control
Sub-cooler
Main evaporator= C3F8 condenser
Restrictors
HEAT LOADa.k.a. detector
R404A
C3F8
R404A
C3F8
Can adjust C3F8 flow!
04/18/23 Auke-Pieter Colijn 8
C3F8 Cooling@CERN
A
BC
E1. A-B: compression
2. B-C: condensing
3. C-D: sub-cooling w. heat exchanger on outlet
4. D-E: expansion
5. E-A: absorb heat from detector (+ sub-cool inlet)
DLIQUID
GAS+LIQUID GAS
P [b
ar]
Enthalpy [J/g]
04/18/23 Auke-Pieter Colijn 9
C3F8 Cooling@NIKHEF
ABC
D
E
1. A-B: condensing
2. B-C: sub-cooling
3. C-D: pump to 12bar
4. D-E: expansion
5. E-A: absorb heat from detector
P [b
ar]
Enthalpy [J/g]
What is BAD about point E?
LIQUID
GAS+LIQUID GAS
04/18/23 Auke-Pieter Colijn 10
C3F8 Cooling@NIKHEF
Enthalpy [J/g]
1. A-B: condensing
2. B-C: sub-cooling
3. C-D: pump to 12bar
4. D-E: heating
5. E-F: expansion
6. F-A: absorb heat
AB
D E
F
C
LIQUID
GAS+LIQUID GAS
P [b
ar]
04/18/23 Auke-Pieter Colijn 12
Run: Temperature
Start-up Run Warm-up
1. I want -10C, I get -10C
2. Need to study fluctuations
04/18/23 Auke-Pieter Colijn 13
Run: Pressure
Inlet pressure = 11bar
Return pressure = 2.8bar = -10 C
Start-up Run Warm-up
04/18/23 Auke-Pieter Colijn 14
Start-up problems
– Lots of leaks
– Broken R404A expansion valve
– Controller (unwired)
– Cooling water stability
– No manual: safety/operations
04/18/23 Auke-Pieter Colijn 15
To do
• Adjust controller: limit temperature fluctuations
• Adjust pressure: 12 bar C3F8
• Adjust flow: each disk circuit
• New pump: need one without leaks
• Heater element: avoid sub-cooled cooling
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