# Presentation: 484644

## The Qweak TargetSilviu CovrigJanuary 30, 2009

- A computational fluid dynamics (cfd) journey
-  cryogenic loop components
-  cell, high power heater, heat exchanger
-  cryogenic pump tests
-  gas service lines
-  safety calculations
-  relief
-  vent
-  release
-  schedule

- January 2009 Hall C Users Meeting

## Qweak Target Players

-  G. Smith and S. Covrig (Hall C – Jlab)
-  D. Meekins (Target Group – Jlab)
-  J. Dunne and D. Brown (Miss. State. U.)
-  + JLab designers and engineers

- Qweak Target Parameters

-  beam: 1.165 GeV, 180 μA, raster 5x5 mm2, FWHM ~ 200 μm
-  lh2: 20 K (3.7 K sub-cooled), 35 psia (2.4 atm) @ 1 kg/s (15 l/s)
-  t = 2.5 g/cm2, 4 % radiator
-  beam heating: 2100 W in lh2, 25 W in 2x0.127 mm Al nipples
-  total design target power: 2500 W = beam heating + losses
-  density fluctuations 45 ppm@250 Hz helicity flip -> 5% increase to detector asymmetry width

- January 2009 Hall C Users Meeting

- The highest power lh2 target in the world

## Computational Fluid Dynamics

-      Software engine for cfd simulations from Fluent.Inc, used in Qweak courtesy of F. William Hersman, UNH
- In Qweak used for designing the cell, hph, hx check-out and a host of simulations for the target safety assessment
- how it works: control-volume-based technique, converts a general scalar equation for
- into a scalar equation to solve numerically
- which is linearized into an algebraic equation
- the equations from all cells form a system of linear algebraic equations that are solved
- Can simulate both steady-state and time-dependent cases

- January 2009 Hall C Users Meeting

## CFD Design Process for the Cell

- Simulations run in steady-state
- Conditions: lh2, beam in nominal conditions, beam heating sourced as uniform power density in both lh2 and Al windows (typically 2.4e8 W/m3 in lh2, 3.9e9 W/m3 in Al), turbulence model used k-ε
- Requirements: minimization of both bulk heating and windows heating, in steady-state cannot estimate ⁄ on the scale of the helicity frequency
- Started with a G0-type longitudinal flow cell (4 cases modeled)
- Converged on a transverse flow cell (>4 cases modeled), which became the Qweak target cell
- NB. without cfd the Qweak target cell would have been a G0-type cell

- January 2009 Hall C Users Meeting

- 2 liters cell

## Lh2 Flow and Density

- <vt>bv = 2.5 m/s

- <Δρ⁄ρ>bv = 0.74 %

- Δp = 0.32 psi@1 kg/s

- <vt>bv = 0.28 m/s
- <v||>bv = 3.8 m/s

- Δp = 0.27 psi@1 kg/s

- <Δρ⁄ρ>bv = 1.82 %

## High Power Heater

- Simulated 8 cases with fluent, narrowed down 2 models that work for us

- Requirements: keep H2 liquid, fit inside 3” pipe, low Δp, 1.2 Ω total
- Conditions:
-  LH2 in at 35 psia, 19 K, 1 kg/s (boils at 23.7 K)
-  coils wire NiCr-A alloy, 13AWG (0.9144 mm radius)
-  2500 W heating in the bulk
-  g10 support with 1.5 mm radius holes for wires
- Results:
-  found 2 models that work, 6v = 4-coil model and 8v = 2 coil model
-  4-layer model delivered to Jlab from MSU (J. Dunne & D. Brown)

| Model | L/T/G/p |  |  | q
W/cm2 | <T>
K | Tmax
K |  |  | Δp
psi |  | <h>
kW/m2K |  | 
W | Pin
psia | G10
holes |   |
| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |
| 6v | 4/23/13/2D |  |  | 3.52 | 22.9
23.5 | 30
31.5 |  |  | 0.323 |  | 10.8-12.1 |  | 2507 | 35 | y/y |   |
|  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |   |
| 8v | 2/36,28/13/2D |  |  | 4.02 | 23.05 | 25.86 |  |  | 0.303 |  | 12.68
12.82 |  | 2499 | 35 | y/y |  |
|  |  |  |  |  | 23.00 | 25.18 |  |  |  |  |  |  |  |  |  |  |
|  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |

- January 2009 Hall C Users Meeting

## 4-layer and 2-layer HPHs

- January 2009 Hall C Users Meeting

- lh2 flow

## Heat Exchanger

- Cooling power design 3000 W

- Designed by the JLab target group
-  3 fin-tube coils in parallel in 3 sections, fully balanced (same pressure drop in all 3 circuits)
-  it is a hybrid hx, getting both 4 K (2 coils) and 15 K (1 coil) He coolant
-  designed for: 500 W cooling from 15 K circuit @17 g/s and 2500 W cooling from 4 K circuit @25 g/s
-  estimated lh2 pressure drop 0.6 psi@1 kg/s
-  24 liters of lh2

- January 2009 Hall C Users Meeting

- 87.3 cm long, 27.3 cm diameter

## Cryogenic Pump

- Assembled in-house (D. Meekins): Al turbo-charger impeller for car racing on a 3⁄4” SS shaft of a 1HP inverter-duty, 29 Hz/ 230 V/ 2.8 A Baldor motor (max 100 Hz)
- Requirement: 1.5 psid@15 liters/s@20 K in lh2

- January 2009 Hall C Users Meeting

##  LN2 Pump Tests

-  1st  try 10.27.08, pump fully assembled, closed loop – starts at low f, goes to 100Hz and seizes at re-start (chocked flow suspected)
-  2nd try 10.29.08, pump fully assembled, open loop, seizes above 5 Hz (bearing suspected)
-  3rd try 11.03.08, pump fully assembled, open loop impeller freezes at low f in LN2 during cool-down (bearing suspected)
- 4th try 11.06.08, motor only, assembled in its house with one new bearing, controller overloads at low f (after settling in LN2)
- Diagnostics:
- controller bridged to motor and power line
- need new bearings
-  5th try at RT in water, works like a charm

- Expected 1.4 psid at 5 l/s in LN2

- January 2009 Hall C Users Meeting

## Pump Tests Pictures

- Measured in H2O
- 1.1 psid at 10 Hz
- 5.4 psid at 30 Hz

- January 2009 Hall C Users Meeting

## Gas Panel and Service Lines

-  functions: provide gases to the target loop (pumping, purging, normal running), relieve the cryogenic loop safely in a breach of vacuum, pressure buffer, pressure monitoring
-  bought ASME stamped MVs and RDs (for both relief and vent lines)
-  will use explosion proof PTs, DPT off the G0 panel
-  manufacturing will proceed once the pump is off the table

- 6000 gal ballast capacity outside Hall C, at 66 psia RT H2

- January 2009 Hall C Users Meeting

## Target Safety

- Nominally lh2: 54 liters (3.9 kg), 35 psia, 20 K – thermal energy in the target cold 15.5 MJ
- Risks: ODH (pressure system/cryogenics), flammability (fire/explosion)
-     thermal energy from combustion 556 MJ (would cause an 18 ̊C increase in Hall C)
- There are 2 containment boundaries for lh2, the cryogenic loop and the target chamber
- Relief = target chamber vacuum breach, cryogenic loop intact
- Vent = cryogenic loop breaks, target chamber intact
- Release = both the loop and the chamber breach -> H2 in Hall C
- two independent calculations of overpressure that concur for relief and vent
- for 2” relief pipelines, mass rate of 105 g/s causes Δpmax = 14.6 psi or pmax = 81 psia
- for 3.5” vent lines, mass rate of 171 g/s causes Δpmax = 7 psig
- fluent time-dependent simulations for 2 different vent events and three cases of H2 release in Hall C
- for 3.5” vent lines, in 3.1 sec, mass rate 210 g/s causes Δp = 13 psig (and rising), in disagreement with the calculation (the cfd simulation accounts for the time-evolution of the process, the calculation does not!)

- January 2009 Hall C Users Meeting

## Fluent Vent Simulations

- Mitigate BLEVE

## H2 release in Hall C

-  3 cases studied, H2 escapes through a 2” diameter hole in the scattering chamber at room temperature (case 1 - hole in the bottom plate, case 2 – hole in the top plate, case 3 – hole in the side-wall)
-  first 20 s H2 out at 200 g/s, next 35 s H2 dispersion
-  8” active/passive outlet vent on top of the dome, 8” active inlet air vent on side of the Hall C wall were considered
-  Hall C volume 26e3 m3, escaped H2 expands to 45 m3@RT (no ODH)
-  H2 flammability/deflagration range in air 4-74% by volume (sub-somic waves)
-  H2 detonation/explosion range in air 18-54% by volume (super-sonic waves)
-  two movies made for each case, RED  = flammability, detonation ranges respectively
-  most likely safety risk event: a H2 fire, small hole could cause sonic boom (vmax through 2” hole 1350 m/s in H2)
- Will have to consider mitigating possible ignition sources for fire

- January 2009 Hall C Users Meeting

## Slide 16

## Slide 17

## Slide 18

## Slide 19

## Target Schedule

- Pre-Installation
-  complete design of major subsystems by Feb09
-  assemble it in the test lab beginning of summer09
-  cold He tests in the test lab summer09 (need a complete loop)
-  safety review spring-summer09 (when design and certification ready)
- Installation
-  target window 2.03.10 – 4.28.10
-  gas panel                    2.04
-  alignment and survey 3.04 – 3.05
-  pump-out/leak check 3.10 – 3.12
-  safety walkthrough
-   & as built review        4.08 – 4.14
-  LNeon test                4.15 – 4.19
-  LH2 no-beam tests    4.23 – 4.28 ...

- January 2009 Hall C Users Meeting

## Gate valve and beam line

- Vacuum window missing

- P. Degtiarenko
-    1 MRad/h

## Motion Mechanism 

-  vertical lifter
- 24” travel, 6 positions
- spare limit switches, relays and dc power supplies procured
- has to be thoroughly tested in the test lab
-  horizontal motion
- 2” travel
- brake and limit switches ordered
- 900, 10:1 gear box was degreased and packed with vacuum grease
- the Phytron motor is the first target component controlled from the target-IOC
-  has to be tested in the test lab

- MSU logic diagram for the cryogenic loop vertical lifter using IDC-S6961

- January 2009 Hall C Users Meeting

## Downstream Gate Valve

- 16” all Aluminum, special design at $11.9k
- There is no thin window on the scattering chamber

- Made by Vacuum Research Co.
-  closes on power failure
-  extended body
-  non-magnetic
-  material certifications provided
-  closing time ~5 sec
-  24 VDC explosion proof solenoid
-  position/limit switches explosion proof for class 1, division 1, group B (H2)
-  has Buna O-rings, will change with metal ones