Cryogenic helium circulation pumps for forced flow cooling · Cryogenic helium circulation pumps...

Cryogenic helium circulation pumps for forced flow cooling | H. Neumann, G. Zahn | March 2009 www.kit.edu

Cryogenic helium circulation pumps for forced flow coolingInstitute for Technical Physics

Holger Neumann, Gernot Zahn

Cryogenic helium circulation pumps for forced flow cooling | H. Neumann, G. Zahn | March 2009

KIT – die Kooperation von Forschungszentrum Karlsruhe GmbH und Universität Karlsruhe (TH)

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Content

Advantages of Helium circulation pumps in forced flow cooling loops

History and development of Helium pumps

Different types of Pumps pistoncentrifugalthermo mechanical

Requirements for ITER

Existing Helium pumps in the research institutes of Europe and Japan

Development for ITER and test option for the pumps

Conclusions



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Advantages of Helium circulation pumps in forced flow cooling loops

Separation of refrigerator and superconducting coil cooling loop powered by He-pumps

Advantages in high flexibility concerning

mass flow rate

pressure ⇒ temperature

pressure drop

heat load

Important benefit after fast discharge or quench

Possibility to reduce mass flow in coil

Independent control of heat load from refrigerator

Refrigerator

Superconducting coil

Control dewar

Compressor

LHe

JT



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Development of Helium pumps

1977: Start of development in FZK

One cylinder piston pump for forced flow cooling test loop with a LCT dummy conductor

This pump was developed in collaboration with the industry (Linde)

Design parameter

mass flow: 20 g/s

pressure head: 3 bar

operating pressure range: 3 – 10 bar



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Development of a three cylinder piston Helium pump

1982: Development of a three cylinder piston pump for the test of the EU-LCT coil

This pump was developed in collaboration with the industry (Linde)

Design parameters:mass flow: 150 g/spressure head: 3.5 baroperating pressure range: 3 – 10 bar

Characteristic curve:very steep ⇒mass flow rate almost independent of

pressure head

Further advantage:low heat load because of long distance between the piston submerged in liquid Helium and gear box at room temperature

With this pump the LCT, POLO, W7-X demo and TFMC model coils have been tested and the pump is still used in FZK

60 80 100 120 140 1600,0

0,5

1,0

1,5

2,0

2,5

3,0

3,5

Temperature = 4.4 KInlet pressure = 3.5 bar

C:/origin/P280F

200 rpm 250 rpm 300 rpm

Pre

ssur

e he

ad

∆∆ ∆∆p [b

ar]

Mass flow rate [g/s]



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Development of a Helium centrifugal pump

1989: Development of a centrifugal pump for the operation of the LCT coil at 1.8 K (He II)

This pump was developed in collaboration with the Walther-Meissner-Institut

Design parameters:mass flow: 50 g/spressure head: 400 mbaroperating pressure range: 3 - 20 bar

Characteristic curve:very flat sufficient for reliable cooling of the winding of the LCT coil with a mass of 20 t during energizing, stable operation (19 kA) and dump

Advantages of this pump:small dimensions (diameter 50 mm, height 210 mm)superconducting motormagnetic bearings

10 20 30 40 50 6050

100

150

200

250

300

350

400

N.100 1/s N.120 1/s N.140 1/s N.160 1/s N.180 1/s N.200 1/s

Pre

ssu

re h

ead

[m

bar

]Mass flow rate[g/s]



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Development of a thermo mechanical pump

1990: Development of a thermo mechanical pump (Fountain pump) for the operation of the LCT coil at 1.8 K (He II)

This pump was developed in FZK

Design parameters:mass flow: 30 g/spressure head: 450 mbaroperating pressure range: 3 - 20 mbar

Characteristic curve:can be influenced by the cold valve sufficient for reliable cooling of the LCT coil during energizing, stable operation (14 kA) and a fast discharge

Big advantage of this pump:heat from the coil and the transfer lines can be used as energy for the circulation of the HeII

Disadvantages:large dimensions of the pump (diameter 300mm, height 650 mm)operation only in He II below 2.2 K



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Development of a larger centrifugal pump

Motor chamber

Motor

Watercoolingchannels

Bearings

He inlet

Impeller

Flange at room temperature

2001: Development of a larger centrifugal pump for the test of the TFMC as redundancy to the two already installed piston pumps with a mass flow rate of 150 g/s each

This pump was developed by Barber & Nichols

Design parameters:mass flow: 300 g/spressure head: 3.5 baroperating pressure range: 3 - 20 bar

Big advantage of this cartridge pump design: the complete pump can be removed or exchanged without opening lines or the cryostatThe impeller can be easily exchanged for an adjustment of the characteristic to the cooling loop



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Characteristic of the large centrifugal pump

16:2016:40

17:0017:20

17:400

2500

5000

7500

10000

12500

15000

17500

20000

0

50

100

150

200

250

300

350

400

0,0

0,5

1,0

1,5

2,0

2,5

3,0

3,5

4,0R

ota

tio

n s

pee

d [

1/m

in]

Time

Date:14.09.04

SI290 [1/min] Rotation speed MFI266 [g/s] Mass flow rate

Mas

s fl

ow

rat

e [g

/s]

DP Pressure head

Pre

ssu

re h

ead

[b

ar]



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Characteristic of the large centrifugal pump

0 100 200 300 4000,0

0,5

1,0

1,5

2,0

2,5

3,0

3,5

4,0

Design N5000 N7500 N10000 N12500 N15000

Pre

ssu

re h

ead

[b

ar]




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Characteristic of the large centrifugal pump including the characteristic of the cooling loop

The high efficiency of a centrifugal pump exists only in a very limited area

The characteristic of the cooling loop must be well known for the design of the pump because it should match with the high efficiency region

Characteristic of the cooling loop



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Cryogenic efficiency of the centrifugal pump

0 50 100 150 200 250 300 350 400 4500,20

0,25

0,30

0,35

0,40

0,45

0,50

Eff

icie

ncy


N5000 N7500 N10000 N12500 N15000 )hh(mP 12real −⋅= &

ρ∆⋅= pm

Ptheo

&

real

theo

PP=η

Calculation of the efficiency



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Cooling system of ITER including He circulation pumps



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Requirements of He circulation pumps for ITER

D. Henry, J.Y. Journeaux, P. Roussel, F. Michel, J.M. Poncet, A. Girard, V. Kalinin, P.Chesny: “Analysis of the ITER cryoplant operational modes”; Fusion Engineering andDesign 82 (2007) 1454–1459

ITER expected operating conditions for cold compressors and cold circulatorsITER-340D110-0000003, By ITER-CEP-PE-CSE, 27/11/2008

4.5 K; 2.0 kg/s, ∆p ~ 0.9barCold circulating pump PF&CC windings

5.0 K; 2.0 kg/s, ∆p ~ 0.9 barCold circulating pump CS windings

5.0 K; 2.5 kg/s, ∆p ~ 1.8 barCold circulating pump TF windings 11.4 kW for all pumps

5.0 K; 3.0 kg/s, ∆p ~ 0.5 barCold circulating pump structure

Heat loadOperation conditionsSHe-pump

4.2 K; 2.0 kg/s, ∆p ~ 0.65barCold circulating pump PF&CC windings

4.2 K; 2.0 kg/s, ∆p ~ 1.2 barCold circulating pump TF windings11.4 kW for all pumps



4.2 K; 2.0 kg/s, ∆p ~ 1.0 barCold circulating pump PF&CC windings

4.2 K; 2.5 kg/s, ∆p ~ 1.5 barCold circulating pump TF windings11.4 kW for all pumps



V. Kalinin, E. Tada, F. Millet, N. Shatil: ” ITER cryogenic system”; Fusion Engineering and Design 81 (2006) 2589–2595



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Existing Helium pumps in the different research institutes and requirements for ITER

0

0,5

1

1,5

2

2,5

3

3,5

4

0 500 1000 1500 2000 2500 3000 3500

mass flow [g/s]

pre

ssu

re h

ead

[b

ar]

existing pumps

ITER [1]

ITER [2]

ITER [3]

FZK

JAERI

ATLASTF windings

CS windings

PF&CC windings pump structures

η = 0.7

η = 0.5

η = 0.72



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Proposal for a test loop in TOSKA

B300

SHe-pump

Refrigerator2 kW, 4.4 K

Possibility of Installation and test of pumps in TOSKA

Advantages

existing facility

only small modifications and additional equipment e.g. heat exchanger needed

sufficient cooling capacity with existing 2 kW-Refrigerator

cooling capacity can be increased for a limited time by decreasing the LHe level in B250

Gasometer

B250



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The TOSKA facility and the 2 kW refrigerator



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The TOSKA facility and the 2 kW refrigerator

671 kW21 g/s----68 g/s6 Pure liquefaction

614 kW9.1 g/s-----5 Pure liquefaction

610 kW--1440 W---4 Pure refrigeration

847 kW8.8 g/s1000 W400 W700 W-43 g/s3 Full load

819 kW12.3 g/s1000 W230 W500 W-50 g/s2 Stand-by

855 kW9 g/s1000 W400 W700 W5.5 g/s-1 Basic

70 K4.4 K3.3 KLHeLN2

El. power consumption of the compressors

Liquefactionrate

Refrigeration capacityPrecoolingwith

Mode



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Conclusion of the pump development

Each of the existing Helium circulation pumps was working very well sometimes for a long time

The mass flow rate of all the pumps used up to now is much below the requirements for ITER which are in the range between 1.5 kg/s to 3 kg/s

The cryogenic efficiency of the existing pumps is around 50 % but for ITER 70 % is mandatory

A development of a appropriate pump by industry is indispensable

The characteristic of the cooling system must be well known for an appropriate design of such a pump which should working in the region of high efficiency

The new developed Helium circulation pumps must be tested and ifnecessary optimized before installation in ITER



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