C.KotnigFCC Design Meeting 12.11.2015 FCC Beam Screen cooling Claudio Kotnig

C.Kotnig FCC Design Meeting 12.11.2015

FCC Beam Screen cooling

Claudio Kotnig

http://doc.cern.ch/archive/electronic/cern/others/PHO/photo-bul/bul-pho-2007-046_01.jpg


C.Kotnig FCC Design Meeting 12.11.2015 2

Content

1. New Beam Screen Design2. Beam Screen Cooling – Sector design

a) Basic hydraulic schemeb) Header and magnet string design

3. Modifications of the basic hydraulic scheme4. Transient modes: Beam Injection5. Summary




New Beam Screen Design

Small CB C10

Small CB O4

Big CB C8

Big CB O4

DT ≈ 2 - 3 K

Antechamber

DT ≈ 1 K

Thermal comparison of the examined designs

Higher temperature range available for extracting the heat→ Less mass

flow→ Less pressure drop→ Less exergy losses





Small CB C10

Small CB O4

Big CB C8

Big CB O4

ACap ≈ 68.4 mm2

ACap ≈ 26.2 mm2

ACap ≈ 9.6 mm2

ACap ≈ 1.8 mm2

Atot ≈ 274 mm2

Atot ≈ 105 mm2

Atot ≈ 77 mm2 Atot ≈ 18 mm2

Antechamber

ACap ≈ 57.6 mm2Atot ≈ 115 mm2

dhyd ≈ 6.14 mm

dhyd ≈ 2.81 mm

dhyd ≈ 3.5 mm dhyd ≈ 1.5 mm dhyd ≈ 6.03 mm

Hydraulic comparison of the examined designs

Hydraulic performance should be between Big CB O4 and Small CB O4




Large controlling effort Investment costs Down time due to component failure

≈

≈

≈

Beam Screen Cooling – Sector design

FCC sector design:

1. Control Valves+ Minimizing total mass flow+ Individual control of single magnet strings+ High efficiencies and stable operation in non-

nominal modes

→ valves, but minimize necessary amount

→ Parallel flow scheme with possible advantages compared to counter flow scheme, if no valves would be used

2. Flow direction → counter flow scheme3. Assembly

scheme+ Large temperature range

available Variable compressor inlet conditions + High pressures in the magnet strings Large valves necessary

+ High supply pressures → smaller pressure losses+ High supply pressures → smaller pressure ratios

4. Supply pressure→ supply pressure 50 bar→ assembly scheme HX1 - C – HX2 – MS - V





Pressure drop in beam screen and headers is a crucial influence quantity for the necessary electrical power

Pressure losses can be reduced with• increasing header

diameter→ high investment costs and

necessary space• shorter magnet strings → many valves necessary

Influence on the exergetic efficiency by variation of these parameters on the hydraulic schemes?

• Supply pressure p0 = 50 bar• Isentropic efficiency of the (cold) compressor hs = 0.7





Exergetic efficiency z vs. header diameter dH for 1, 4 & 7 magnets per MS




Modifications of the basic hydraulic scheme

Example: Distribution of pressure losses in magnet strings (7 magnets)

Installing a bypass at the last MS

• increases the total mass flow

• deacreases the basic pressure drop in the last magnet string

MS inlet temperature increases due to thermal shielding of the supply header

mBP = 0.43 kg/s




Exergetic efficiency z vs. bypass mass flow mBP for 1, 4 & 7 magnets per MS


zmax zmaxzmax





Example: Distribution of pressure losses in magnet strings (7 magnets)

→ No thermal shielding tasks for the supply header

Basic (minimal) pressure drop increases with MS inlet temperature

→ MS inlet temperature low and almost constant

Basic: Dp0 ≈ 8 bar

Bypass: Dp0 ≈ 5.5 bar

RH-Shield: Dp0 ≈ 4 bar










Warm compressor cycle (TU Dresden)

• Depending on pressure drop in the sector, the necessary power consumption including the Nelium-Cycle, could be lower than in a cold compressor cycle

• A warm compressor is less prone to failure and easier to handle

• A warm compressor could be used for cool-down and warm-up tasks

• A warm compressor could have advantages regarding load changes (e.g. inserting the beam after working a long time in standby mode, etc. )

Warm compressor cycle

TaCold compressor cycle

Neliu

m

cycle

Neliu

m

cycle









hs = 0.7 (cold compressor)

hs = 0.83 (warm compressor)

hth = 0.42 (Nelium cycle)


Beam screen sector cycle + Nelium cycle

Shie

ld

1M

Shie

ld

4M

Shie

ld

7M

Bypa

ss

4M

Bypa

ss

7M

Bypa

ss

1M

Basic

1M

Basic

7M

Basic

4M

1 MW ≙ 36,000,000 CHFin 10 years of FCC operation

1)2)

3)





1 2 3# magnets per string 4 7 7# valves 138 79 79total mass flow 5.68 kg/s 5.08 kg/s 5.08 kg/sbypass mass flow 0.15 kg/s (≈ 2.6

%)- -

temperature last MS inlet

44.6 K ≈ 40 K ≈ 40 K

pressure drop last MS 2.02 bar 3.84 bar 3.84 barpressure drop / ratio 2.8 bar / 1.06 4.6 bar / 1.10 4.6 bar / 1.10total power consumption

8.3 MW 8.4 MW 9.2 MWadditional piping yes yes yeswarm compressor benefits

no no yes

temperature HX inlet 60.0 K 62.5 K 62.5 K

?

?




Transient modes: Beam injection

Similar increase of current like in the LHC → standby to nominal operation in 27 minutes

in

nom

nom

in

nom

redpp

TT

m

mm

in

incor

pTmm 101325

15.288




Transient modes: Beam injection

Fast increase of heat to extract (especially at the end of the injection process)→ during normal physic’s runs the working point of the

compressor shall be kept constant artificially

Only during longer breaks, the load on the compressor shall be decreasedStarting physic’s runs again → reach working point by closing valves before magnet ramping starts

Tin = const.pin = const.m = const.




Summary

SummaryThe pressure drop generated in the sector is the crucial quantity for the necessary electrical power – the design of the hydraulic scheme is decisive for the final pressure drop.

Based on the actual sector design, hydraulic schemes with a cold compressor are the better choice w.r.t. the power consumption.Warm compressors have advantages like multipurpose usage and easier handling.The investigation of transient processes could bring the choice regarding the type of used compressor to a head, if one concept clearly is superior during transient modes.

The separate shielding scheme is the preferable choice to minimize the necessary power consumption for cooling magnet strings of reasonable lengths.



C.Kotnig FCC Design Meeting 12.11.2015

19

Thank you very much for your attention





New Beam Screen Design developed by the VCS-Group at CERN

• Shield (Antechamber)

• Beam Tube

• Capillaries

• Copper layer(s)

Cold Bore

41





Heat loads affecting the Beam Screen:

• 28.4 W/m (synchrotron radiation)

• 3 W/m (resistance image current)

o Small dispersion angle (≈ 10º)

o Large component in axial direction

→ parts affected by the synchrotron radiation depend on the reflection and the distances between the stabilizing ribs

o Only one direction

o Heat transition via weld contacts





≈ 56 K

< 41 K

40 K

Temperature difference < 1 K(former designs: ≈ 2 - 3 K)

→ Larger temperature difference available

• less exergy losses

• less mass flow





Solutions for provide compressor with constant inlet conditions

Second HX

Bypass

+ Low investment costs and necessary space

High investment costs and necessary space

+ Possibility of using different temperature levels

Temperatures clearly below 40 K necessary




Basic Beam Screen Cooling System




Modifications of the Basic Beam Screen Cooling System











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C.KotnigFCC Design Meeting 12.11.2015 FCC Beam Screen cooling Claudio Kotnig