CEA-Grenoble / DSM / DRFMC / Service des Basses Températures / B. rousset 1 24/04/2007

1 bar4.2 KVapour

Two-phase HeII LiquidHe

Slope batween0-1.4 %

Longitudinal T

transverse T1 bar4.2 KVapour

Two-phase HeIITwo-phase HeII LiquidHe

Slope batween0-1.4 %

Longitudinal T

transverse T

LHC cooling scheme

magnet

1 bar4.2 K

Pressurized HeII bath

Vapour

T2

Liquid

Saturated He II bath

T1

A Tore Supra like cooling scheme ?

Any instabilities ?

Enhance transverse heat transfer by use of corrugated pipe ?

Two-phase flow pressure drop compatible with longitudinal DT ?

CEA-Grenoble / DSM / DRFMC / Service des Basses Températures / B. rousset 2 24/04/2007

CEA-Grenoble / DSM / DRFMC / Service des Basses Températures / B. rousset 3 24/04/2007

Comparison between experiments and theoretical model

0

50

100

150

200

250

300

350

0 2 4 6 8 10 12 14

Vgs (m/s)

P (P

a)

Data Slope=0 % m= 7.2 g/s T=1.77 K

Model developped at CEA/SBT

LHC nominal operation

Main results concerning pressure drop

CEA-Grenoble / DSM / DRFMC / Service des Basses Températures / B. rousset 4 24/04/2007

0

10

20

30

40

50

60

1 3 5 7 9 11Vgs (m/s)

Wet

ted p

erim

eter

(%

)(%

)

Data 7.2 g/s 1.77 K

Code

Horizontal line

Low vapour velocity No liquid droplets

High vapour VelocityLots of droplets

Main results concerning heat transfer

LHC nominal operation

CEA-Grenoble / DSM / DRFMC / Service des Basses Températures / B. rousset 5 24/04/2007

• From this results on co-current HeII two-phase flow (no instability for descending co-current two-phase flow, longitudinal and transverse DT small enough to correctly cool down the magnets) we concluded that this cooling scheme will be used to cool down the LHC superconducting magnet strings.

• For upgrade of LHC, the use of smaller sector with high vapour velocity will also meets the requirement.

Conclusion