1. SC1R Cold Box PDR: Process Requirements
SC1R Cold Box Preliminary Design Review
N Hasan
Saturday, November 10, 2018

2. Presentation Outline CEBAF Cryogenic Load CEBAF 2K Cryogenic Systems
- Operating Philosophy
- Equipment
- Distribution
Process Requirements / Considerations
- Cold Compressors
- 4K-2K Heat Exchanger
- Internal Piping
Proposed P&I Paths
Commissioning Plan
Summary
SC1R Cold Box PDR: Process Requirements

3. CEBAF Cryogenic Load Continuous Polarized Electron Beam up to 12 GeV
55 Full Size Cryomodules (C50/C75/C100)
2 Quarter Size Cryomodules
Cryogenic Load Split between –
a) North LINAC (27.25 CMs)
b) South LINAC (25 CMs)
c) LERF (3.25 CMs)
Prescribed Energy of 1150 MeV/LINAC/pass1
Static Heat in-leak to LHe bath: 22 W/module
- Calculated, based on total electric heat applied and TD read-backs
RTL Heat in-leak to primary return flow:
a) North LINAC 600 W
b) South LINAC 600 W
c) LERF W
Fig. Schematic of CEBAF at 12 GeV
1 Zhang et al., Optimization of the RF cavity heat load and trip rates for CEBAF at 12 GeV, IPAC2017
SC1R Cold Box PDR: Process Requirements

4. CEBAF Cryogenic Load (contd.)
Fig. RF load at each LINAC under different operating conditions 1
RF Heat Load at each LINAC (North / South): approx W
- can be as high as 3100 W
Electric Heat Load (Pressure Compensation): approx. 250 W
Total Heat Load per LINAC: approx W
Flow Required to support Load: approx. 200 g/s
- based on approx. 80% quality, 3.0 atm, 4.5 K primary supply flow and 37.5 mbar
vapor pressure
SC1R Cold Box PDR: Process Requirements

5. CEBAF Cryogenic Load (contd.)
Operating Pressure:
40.0 mbar
6.0 GeV Operations
36.5 – 37.5 mbar
12 GeV Commissioning
LINAC Pressure Optimization
(Spring 2017 Run)
Tests performed at operating pressures ranging from 37.0 mbar to 41.0 mbar
38.5 mbar (maximum allowable)
Cavity tuning
Fig. North LINAC Operating Pressure and Energy Reach2
2Cryo Pressure / SRF Optimization – Fall 2016,
SC1R Cold Box PDR: Process Requirements

6. CEBAF 2K Cryogenic Systems – Operating Philosophy
2K Cryogenics for Large Systems:
All cold compressors (CEBAF and SNS)
Pressure stability demonstrated to be better than +/-0.1 mbar
Partial cold compressors (CERN)
Pressure stability of +/- 0.3 mbar, which makes the tuning of SRF cavities very difficult and unstable
CEBAF 2K Cryogenic Systems:
5 Cold Compressors in Series
CC4 Speed maintains flow.
CC1-CC3 speed maintained by speed ratio with CC4.
CC5 speed maintains constant pressure ratio across.
Pump down follows a pre-defined path
-CC speed, flow as function of RTL pressure,
look-up table, obtained experimentally
SC1R Cold Box PDR: Process Requirements

7. CEBAF 2K Cryogenic Systems - Equipment
SCN (SC2)4
Commissioned 1999 (JLab, L’ Air Liquide).
5 Cold Compressors (CC1-CC5).
Design max. CC flow ~250 g/s.
Design CC return temperature to 4KCB is ~30K.
Max. CC Inlet / Outlet Pressures: 28 / 1200 mbar (Pr. ratio 42).
3 NTU 4K-2K Heat Exchanger (added capacity).
SCM (SC1)3
Commissioned 1994 (CVI Corp., L’ Air Liquide).
Initially 4 Cold Compressors (CC1-CC4), CC5 added later.
Design CC flow g/s (up to 285 g/s during pump-downs).
Design CC return temperature to 4KCB is ~30K.
Max. CC Inlet / Outlet Pressures: 28 / 1189 mbar (Pr. ratio 42).
Initially 2 NTU 4K-2K Heat Exchanger. Upgraded to 3 NTU later.
3 CEBAF Cold Compressors Characteristics, L’Air Liquide Datasheet
4Design, Fabrication, Commissioning, and Testing of a 250 g/s, 2-K helium cold compressor system, Ganni et al., Proc. of CEC, Vol. 47 (2002)
SC1R Cold Box PDR: Process Requirements

8. CEBAF 2K Cryogenic Systems – Distribution System
Two 4.5K Cryo-plants (CHL1, CHL2)
Two 2K Cold Boxes (SCM, SCN)
Three separate LINACs (NL, SL, LERF)
Distribution System –
- Separate Header for Each System
- Re-configurable (U-Tubes)
- Can be Cross-Connected (Valves / U-Tubes)
- Helps operating at reduced capacity if needed (during SAD)
SC1R Cold Box PDR: Process Requirements

9. CEBAF 2K Cryogenic Systems – Distribution System
CHL1 (4K CBX)
CHL2 (4K CBX)
SC1M
SC2N
LERF SL NL
Fig. Simplified Schematic of the CHL-LINAC Distribution System (Primary Returns Only, Typical Config.)
SC1R Cold Box PDR: Process Requirements

10. Process Requirements – Cold Compressors
Simplified Process Model:
Simulated process CC1 suction
Max. Pump-down Flow: g/s
Pump-down Flow Profile: Existing
HX Parameters: HX-10 (SCN)
NTU 3.0
RTL Heat in-leak: 600 W (per LINAC)
Supply Flow Condition: 3.0 atm
4.5 K
Considerations -
Fully Compressible Flow
Single or Dual LINAC Pump-down
Fig. Schematic of the 2K system for the Process Model
SC1R Cold Box PDR: Process Requirements

11. Process Requirements – Cold Compressors (contd.)
Simulated process CC1 suction:
Fig.: Simulated CC1 suction temperatures during pump-down
Fig.: Volumetric flow requirements at CC1 suction during pump-down
SC1R Cold Box PDR: Process Requirements

12. Process Requirements – Cold Compressors (contd.)
Mode of Operation:
Maximum Capacity
250 g/s, 1.2 bar
≤ 30 K
~ 3.0 bar, 4.5 K
Guaranteed mode of operation.
Forms the basis for -
a) maximum volume flow (660 liters/sec)
b) maximum operating speed
For comparison –
JLab SC2: 580 liters/sec
FRIB (Upgrade): 640 liters/sec
LCLSII: 580 liters/sec
≤ 3.6 K
≤ 28.0 mbar
HX-10R
SC1R Cold Box PDR: Process Requirements

13. Process Requirements – Cold Compressors (contd.)
Mode of Operation:
Nominal Capacity
200 g/s, 1.2 bar
≤ 30 K
~ 3.0 bar, 4.5 K
Guaranteed mode of operation.
Nominal turn-down condition.
Forms the basis for (under safe operating point from surge)
a) maximum pressure ratio
≤ 3.8 K
≤ 31.0 mbar
1.5
HX-10R
SC1R Cold Box PDR: Process Requirements

14. Process Requirements – Cold Compressors (contd.)
Mode of Operation:
Pump-down Peak
250 g/s, 1.2 bar
~ 3.0 bar, 4.5 K
Transient State.
Maximum mass flow rate (~250 g/s)
Maximum Acceleration of CCs
≤ 6.0 K
~ 52.0 mbar
HX-10R
SC1R Cold Box PDR: Process Requirements

15. Process Requirements – Cold Compressors (contd.)
Mode of Operation:
Minimum Capacity
170 g/s, 1.2 bar
≤ 30 K
~ 3.0 bar, 4.5 K
Expected mode of operation.
Maximum turn-down mode.
Helps with operation with SLINAC only
≤ 3.6 K
≤ 31.0 mbar
HX-10R
SC1R Cold Box PDR: Process Requirements

16. Process Requirements – Heat Exchanger
Brazed Aluminum Plate-Fin Heat Exchanger:
Stream:
Primary Supply Stream
Primary Return Stream
[Unit]
Flow Rate
250
[g/s]
Operating Pressurea
2.85 (41.2)
(0.5)
[bar]
Inlet Temperature
4.5
2.2
[K]
Outlet Temperature
2.5
3.3
Total Duty
1.5
[kW]
Corrected MTD (max.)
0.59
NTU 3
[-]
Design Temperature
340/2.0
Design Pressure (max.)a
25.2 (350)
7.9 (100)
Frictional Pressure Drop
1.7 2
[mbar]
Inlet Header Size (max.) 4 -
[NPS]
Outlet Header Size (max.)
Inlet Nozzle Size (max.) 10
Outlet Nozzle Size (max.)
Type Connection
Aluminum to Stainless steel transition joint, Slugged, Marked for Cutoff, Pressurized for Shipment
a Values in the parentheses refer to the pressures in psig.
SC1R Cold Box PDR: Process Requirements

17. Process Requirements – Heat Exchanger (contd.)
Is it possible to reduce the HX capacity to meet Cold Box physical sizing constraints?
Higher primary supply temperatures to LINAC.
Reduced dynamic heat capacity of LINAC.
Higher pressure drop (typically) in sub-atmospheric (return) side.
Increases CC speeds for same flow conditions.
Lower CC1 inlet temperature.
Decreases CC speeds for same flow conditions.
SC1R Cold Box PDR: Process Requirements

18. Process Requirements – Internal Piping
Frictional Pressure Drop1:
LINAC Pressure = ΔpRTL + ΔpHX + ΔpIP + CC1 inlet pressure
33.5
[mbar]
CC CC CC3-2 CC2-1 CC1
5.5 mbar
1,0 mbar
1.8 mbar
1.2 mbar
1.0 mbar
1 at maximum flow condition with inlet conditions similar to SC2
SC1R Cold Box PDR: Process Requirements

19. Process Requirements – Internal Piping (contd.)
Design Considerations:
Minimum suction volume required to offset transients during acceleration/deceleration
Parameter
Value
[Unit]
Description
FID 11
[-]
Fluid ID ṁ
250
[g/s]
CC Flow Rate ∆
0.015
[mm]
Absolute Roughness of SS Piping
qin-leak 20
[W]
Heat In-Leak (min.)
CCID 1 2 3 4 5
pin 28 76
182
410
823
[mbar]
Inlet Pressure (Assumed)
Tin
3.6
6.2
9.7
14.7
21.2
[K]
Inlet Temperature (Assumed)
ρin
0.378
0.594
0.908
1.347
1.869
[g/l]
Inlet Density Ṽ
661.2
420.5
275.3
185.7
133.8
[l/s]
Volumetric Flow Rate τ
37.8
0.2
0.15
[sec]
Time Constant (Based on SC2 Process)
Vin 25
0.084
0.041
0.028
0.020
[m3]
Volume Required at Inlet D 6
[in.]
Piping Diameter L -
181.5
89.1
135.2
97.5
Inlet Piping Length (Required)†
SC1R Cold Box PDR: Process Requirements

20. Process Requirements – Internal Piping (contd.)
Design Considerations:
Flow straighteners in inter-stage piping.
Reduces vorticity at CC suction.
May increase inter-stage pressure drop.
Imposes restrictions on minimum piping length between stages.
Per ISO : Annex C (`Etoile Straightener)
Towards CCN+1 suction
From CCN discharge
Fig.: Simulated vortex flow through flow straightener (left) and straight pipe (right)
Fig.: Bellows – straight tube assembly
SC1R Cold Box PDR: Process Requirements

21. Proposed P&I Paths Primary Return – CC Discharge:
SC1R Cold Box PDR: Process Requirements

22. Proposed P&I Paths (contd.)
Primary Supply – 4KCBX to LINAC:
SC1R Cold Box PDR: Process Requirements

23. Proposed P&I Paths (contd.)
LN Shield:
SC1R Cold Box PDR: Process Requirements

24. Proposed P&I Paths (contd.)
Purge / Clean-up / Warm-up:
SC1R Cold Box PDR: Process Requirements

25. Commissioning Plan Maximum/Nominal Capacity: CHL2 (4K CBX)
SC1R
SC2N
LERF SL NL
SC1R Cold Box PDR: Process Requirements

26. Commissioning Plan (contd.)
Minimum Capacity:
CHL2 (4K CBX)
CHL1 (4K CBX)
SC1R
SC2N SL NL
LERF
SC1R Cold Box PDR: Process Requirements

27. Summary CEBAF Cryogenic Load: 3750 W / LINAC ~ 200 g/s CC Flow
CEBAF 2K Cryogenic Systems:
2x 4K Cold Box; 2x 2K Cold Box
Ability to Cross-Connect Loads/Plant
Process Requirements:
Cold Compressors – mbar (CC1 suction); Pressure Ratio: 42
4K-2K Heat Exchanger – 3 NTU, ~ 0.6 MTD
Proposed P&I Paths:
Primary Supply/Return; LN Shielding for 2K piping
Purge / Clean-up / Warm-up piping
Commissioning Plan (Preliminary):
Commissioning with CHL2
SLinac, LERF
SC1R Cold Box PDR: Process Requirements

28. Thank You
Saturday, November 10, 2018