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C3F8 cooling @ NIKHEF

DesignCompare

Does it work?

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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

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FRONT VIEW REAR VIEW

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T sensors

Freon “doggy”

snoop

P sensors

My favorite tools

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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

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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

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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!

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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]

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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

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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]

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Run it!

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Run: TemperatureStart-up Run Warm-up

1. I want -10C, I get -10C

2. Need to study fluctuations

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Run: Pressure

Inlet pressure = 11bar

Return pressure = 2.8bar = -10 C

Start-up Run Warm-up

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Start-up problems

– Lots of leaks– Broken R404A expansion valve– Controller (unwired)– Cooling water stability– No manual: safety/operations

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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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Summary• Cooling plant @ NIKHEF

1. Different design2. Works3. Make final adjustment