4th Thermosyphon Workshop 1

Full Scale Thermosyphon Design Parameters

and Technical Description

Jose Botelho DireitoEN/CV/DC

19 November, 2010

4th Thermosyphon Workshop 2

Outline

• Design specifications• Thermodynamic cycle• Power requirement and power consumption• Pipe sizing and insulation• Condenser/Tank design

19 November, 2010

4th Thermosyphon Workshop 3

Thermosyphon Design Specification

19 November, 2010

Parameter Actual Plant Thermosyphon Design Specification

Flow of C3F8 at full power 1.1 kg/s (1) 1.2 kg/s

Liquid pressure at the supply distribution lines (plant side) 15 bara 15 bara (Height required = 95 m)

Temperature at the supply rack 20°C 20°C

Nominal pressure of the C3F8 at the return rack (plant side) 0.8 bara 0.5 bara (Psat=0.31 bara;Tsat=-60°C)

Temperature at the return rack 20°C 20°C

Maximum operating pressure PN25 PN40

(1) Read from the plant flow meter.

Evaporative /Thermosyphon

Return Rack

Supply RackPin Tin

Pout

4th Thermosyphon Workshop 4

Thermosyphon Basic Scheme

19 November, 2010

4th Thermosyphon Workshop 5

Thermodynamic Cycle

19 November, 2010

12/10/2010 60kW Thermosyphon 6

AB

C

DE

F G H I

JK

LM N O

PI‘

4th Thermosyphon Workshop 6

Cooling and Electrical Power

19 November, 2010

Operation Line0

Description Component Power [kW] Power Type

Point A to B Cooling of the Return vapour Sub-Cooling HX 35 Passive component

Point B to C Return line Return pipe (+) 4 Passive component

Point C to D Condensation Tank Condensation 165 -

Point D to E Sub-Cooling Tank sub-cooling 5.5 -

Point C to E Condensing + Sub-cooling Condenser/Tank (-) 170 Chiller Power

Point E to F Supply line Supply pipe (+) 4 Passive component

Point F to G Heating up to the dew point Electrical Heater (-) 13 Electrical

Point G to H Heating the liquid using the return vapour

Heat Exchanger 35 Passive component

Point H to I Heating to room temperature Electrical Heater (-) 51 Electrical

Point I’ to A Evaporation and super heating Dummy Load (-) 107(1)/22(2)/0(3) Electrical

(1) During the commissioning period only.(2) Start up.(3) Running trough the detector.

4th Thermosyphon Workshop 7

Pipe Sizing and Insulation• Supply Pipe:

– Minimize pressure drop -> Larger diameter.– Minimize liquid volume and cost of pipes and installation -> Smaller diameter.

• Return Pipe: – Minimize pressure drop

• A high pressure drop can force us to decrease saturation pressure, increasing the Chiller cost!

– Minimize cost of pipes and installation

• Insulation:– Minimize heat pick up on the return line.

• taking into account the external wall temperature of the Insulation.– Maximize heat pick up on the supply line.

• Tanking into account the external wall temperature of the insulation.

19 November, 2010

4th Thermosyphon Workshop 8

Pipe Sizing and Insulation: Supply• Pipe Size and Insulation Supply:

– DN50; ΔPfriction=55mbar

– Insulation Thickness: 40mm; ΔTmax/100m=1.8K

19 November, 2010

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0 5 10 15 20 25 30 35 40 45

dT/ 10m [K]

h air [W/m2.K]

DN50 Liquid line; HTCC3F8=329W/m2.K

Ins. Thick 20 mmIns. Thick 30 mmIns. Thick 40 mm

-30

-25

-20

-15

-10

-5

0

5

10

15

20

25

0 5 10 15 20 25Twall Out [°C]

h air [W/m2.K]

DN50 Liquid line; HTCC3F8=329W/m2.K

Ins. Thick 40 mmIns. Thick 30 mmIns. Thick 20 mm

4th Thermosyphon Workshop 9

Pipe Sizing and Insulation: Return• Pipe Size and Insulation Return:

– DN200; ΔPfriction=25mbar; ΔPheight=35mbar (independent from the pipe)

– Insulation Thickness: 40mm; ΔTmax/100m=3.5K

19 November, 2010

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0 5 10 15 20 25 30 35 40 45

dT/ 10m [K]

h air [W/m2.K]

DN200 Vapour line; HTCC3F8=42W/m2.K

Ins. Thick 20 mmIns. Thick 30 mmIns. Thick 40 mm

-5

0

5

10

15

20

25

30

0 5 10 15 20 25

Twall Out [°C]

h air [W/m2.K]

DN200 Vapour line; HTCC3F8=42W/m2.K

Ins. Thick 40 mmIns. Thick 30 mmIns. Thick 20 mm

4th Thermosyphon Workshop 10

Condenser/Tank Design

• Total Cooling Power: 170kW (164.5kW of condensation + 5.5kW of sub-cooling).

• Required flow of C6F14: 40kg/s (ΔT=5K)

– The pressure drop would be too high using only one coolant coil (standard size of ≈16mm ID).

– The solution is the use of a Shell and Tube Heat Exchanger.

19 November, 2010

4th Thermosyphon Workshop 11

Condenser Design

19 November, 2010

Finned External Surface

Smooth Internal Surface

• First Approach* on the Condenser Design:

• HTC on Condensing side: 12 kW/m2.K• HTC on Brine side: 1.1 kW/m2.K• Overall HTC: 253 W/m2.K• Required surface area of heat exchange: 93 m2

• Required number of tubes: 225 (with 3m length; 0.208 m2/m of external finned surface area)• Number of tubes: 253 (12% over surface)• Number of loops: 42• Number of tube passes: 4• Velocity of C6F14: 2.6m/s (Copper alloy needed)• Pressure drop: 1.9 bar

C3F8 vapour inlet (x3)

C3F8 liquid outlet (x3)To liquid tank

3 m

Φ 0.8m

* Calculations will be verified by Claudio Zilio (Padova University)and by the manufacture company.

4th Thermosyphon Workshop 12

Tank Design

• Total required mass of Liquid: 2750kg– Liquid side: 1565 kg– Vapour side: 644kg– Compensation for leaks: 540kg (3kg/day; 180days)

• Maximum volume: 2.15m3 (@32°C)

• Minimum volume: 1.6m3 (@-65°C)

• Approximate recommended total volume of the Tank: 2.5m3

• The possibility of joining the Condenser and the Tank is being studied.

19 November, 2010

4th Thermosyphon Workshop 13

Thermosyphon P&ID

19 November, 2010