The q weak target silviu covrig january 30 2009
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The Q weak 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.

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The q weak target silviu covrig january 30 2009

The Qweak TargetSilviu CovrigJanuary 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





January 2009 Hall C Users Meeting

Q weak target players

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 [email protected] Hz helicity flip -> 5% increase to detector asymmetry width

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

The highest power lh2 target in the world

January 2009 Hall C Users Meeting

Computational fluid dynamics

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
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

2 liters cell

January 2009 Hall C Users Meeting

Lh2 Flow and Density

<vt>bv = 2.5 m/s

<Δρ⁄ρ>bv = 0.74 %

Δp = 0.32 [email protected] kg/s

<vt>bv = 0.28 m/s

<v||>bv = 3.8 m/s

<Δρ⁄ρ>bv = 1.82 %

Δp = 0.27 [email protected] kg/s

High power heater
High Power Heater

  • 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)

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

January 2009 Hall C Users Meeting

4 layer and 2 layer hphs
4-layer and 2-layer HPHs

lh2 flow

January 2009 Hall C Users Meeting

Heat exchanger

  • 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 [email protected] kg/s

  • 24 liters of lh2

Heat Exchanger

87.3 cm long, 27.3 cm diameter

Cooling power design 3000 W

January 2009 Hall C Users Meeting

Cryogenic pump
Cryogenic Pump

Assembled in-house (D. Meekins): Al turbo-charger impeller for car racing on a ¾” SS shaft of a 1HP inverter-duty, 29 Hz/ 230 V/ 2.8 A Baldor motor (max 100 Hz)

Requirement: 1.5 [email protected] [email protected] K in lh2

January 2009 Hall C Users Meeting

Ln 2 pump tests
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)


    • 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
Gas Panel and Service Lines

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

  • 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

January 2009 Hall C Users Meeting

Target safety
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

H 2 release in hall c
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 [email protected] (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

Target schedule

Target Schedule


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)


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
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