Mini-Thermosyphon Test Results

Mini-Thermosyphon Tests Results 1

Mini-Thermosyphon Test Results

Jose Direito et. al. (EN/CV/Detector Cooling)

May 28, 2010


Objectives/Motivations

• Validation of the Thermosyphon concept in a smaller scale (17.4 meters of height).

• Report the behavior of system during Start up/operation/shut down.

• Gain experience on the operation of the plant.

May 28, 2010


General Scheme and Layout @ Blg 191

ΔH

P1

P2 Detector/EvaporatorP3

P2 > P3 > P1

ChillerCondenser

Dummy Load

~18m

May 28, 2010

Natural circulation of the Fluid (C3F8)- On the liquid phase by gravity- On the gas phase by pressure difference

Liquid

Gas


Thermodynamic Cycle

A-B : Condensation and sub-cooling

B-C : Hydrostatic ΔP

C-D : Expansion

D-E : Evaporation and super heating

May 28, 2010

Start-up

Running Cold

Liquid

2-Phase

Gas

Ramp Down

C3F8 Pressure – Enthalpy Diagram


FTPT

Calc. Saturation Temperature

Mini-Thermosyphon Working Principles

May 28, 2010

Conditions to run:- Condenser Sat. Temp. > Liq. Temp.- Liq. Pressure (supply line) > Local Sat. Pressure- Outlet Vapour Temp. > Evap. Temp.

Monitored Parameters:- ΔT = Tsaturation – Tliquid

- ΔP = Psupply – Psaturation (and/or Tsaturation (local) – Tlocal) - ΔT = Tout gas – Tevaporation

Possible Set Points:

- Chiller Set Point (sets the Cond./Evap. Temp.)- Expansion Valve (sets the flow)- Dummy Load Outlet Temperature

C6F14 circuit C3F8

Mini-Thermosyphon Tests Results 6May 28, 2010

Evaporation temperature of -5°CFlow = 30g/s (3kW)

Condenser pressure oscillations of 23mbar

Evaporation Temperature oscillations of 0.15°C

Evaporation temperature of -25°CFlow = 21g/s (2.1kW)

Condenser oscillations of 28mbar Temperature oscillations of 0.4°C

(oscillations can be reduced by installing a pressure regulator)

Stable Running Conditions


35 hours RunMass Flow of 16g/s (1.6kW of Cooling Power); Evaporating at -28°C


Running Conditions at different Temperature and Flow rates

May 28, 2010

Decreasing the flow from 30 to 15g/s:- Higher efficiency on the condensation -> lower evaporation temperatures-The chiller set point should be related to the condenser saturation temperature.

T sat

T liq

T gas

T readout chiller

ChillerC6F14


Starting up and Ramping Down

May 28, 2010

- The condensation on the tank is faster than the sub cooling!- Having the saturation temperature close to the liquid temperature can stop the flow!

22g/s (2.2kW cooling power) – 3:35 hr to go from 25°C to -25°C (ΔT=50K -> 14.3K/hr)


C3F8 flow of 30g/s (~3kW)

2:45 hours to go from 25°C to -25°C (ΔT=50K -> 18.2K/hr)

Flow from 26g/s (2.6kW) to 14g/s (1.4kW)

1:05 hours to go from 25°C to -25°C (ΔT=50K -> 47.6K/hr)

Faster Ramp Down with higher flows


Stopping examples

May 28, 2010

Saturation Temperature got too close to the Liquid Temperature (very low flow)

T sat ≈ T liquidm [g/s]

P [bar]


Stopping examples

Supply Manifold temperature (T06) higher than the local saturation temperature


System Restart after a Stop

May 28, 2010

After the Stop, the Chiller Set Point was increased until the dP indicates that there is liquid on the supply lineThe Flow was then restarted


Optimising and Scaling the Thermosyphon

May 28, 2010

• Because of the High Cost of Chillers for low temperatures:

– Minimisation of the ΔT between the Chiller and the Evaporation Temperature:

• ΔT between the Chiller and the Liquid part of the condenser.• ΔT between the Liquid and the Condensing part of the Condenser.

• Decrease the minimum flow rate necessary to keep the plant running.


Liquid and Saturation Temperatures study

T sat

T liq

T gas

(Chiller Set Point)


Minimisation of the ΔT on the Liquid Part: Insulation

May 28, 2010

Chiller Power

Heat removed from the C3F8

Pick Up Heat

A Proper Insulation is required!


• This ΔT can be minimised but there must be a minimum value to keep the plant running:– Take full advantage of the surface area on the design phase.– Changing the flow rate on the C6F14 circuit according to this ΔT on the final Plant:

• If the ΔT is small then the flow should be decreased and vice versa.• This can also reduce the minimum flow required to keep the plant running.

May 28, 2010

Minimisation of the ΔT (Liquid and Saturation Temperature)

Reduced the C6F14 Flow

T sat

T liq

T gas

(C6F14 Flow)


Behaviour when the Chiller turned off

May 28, 2010

Stopping the chiller and the flow:-It would be possible to restart at least 5 min later.-This time can be increased using a proper insulation.

Stopping the chiller only:-The saturation temperature increases but it keeps running.-The rate at which the temperature increases can be reduced if the chiller pump keeps running.

Chiller Stopped

Valve closed Chiller Stopped


Pixel Stave connected to the Thermosyphon

May 28, 2010

Tests and Results By:Vaclav Vacek, Rene Marek; Czech Technical University – PragueKirill Egorov – CERN

Flow rate on the Half Stave of 1.6g/s; Stave Power of 100W


• The Thermosyphon works!

• Its possible to scale it for different Power, Temperature, and Fluid requirements.

• It is very reliable, since no working components (pumps or compressors) exist on the plant.

May 28, 2010

Conclusions

Mini-Thermosyphon Test Results

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