CFD Analysis of LAr Flow in 35 ton prototype, ProtoDUNE, & LBNF - - PowerPoint PPT Presentation

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CFD Analysis of LAr Flow in 35 ton prototype, ProtoDUNE, & LBNF cryostats Gregory Michna Stephen Gent Aaron Propst Department of Mechanical Engineering South Dakota State University November 10, 2017 Project Goals Study impurity levels

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CFD Analysis of LAr Flow in 35 ton prototype, ProtoDUNE, & LBNF cryostats

Department of Mechanical Engineering South Dakota State University November 10, 2017

Gregory Michna Stephen Gent Aaron Propst

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Project Goals

  • Study impurity levels within a LAr cryostat using Computational

Fluid Dynamics (CFD) simulation methods.

  • Explore effect on impurity levels by changing:

– LAr circulation flow rate and inlet temperature – LAr inlet and outlet locations – Internal electronics heat load

  • Desire a uniform and stable distribution of impurities

11/10/2017 2 Liquid Argon Flow CFD Simulations

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SLIDE 3

Methods

  • Simulate LAr motion due to natural convection (buoyancy)

with Boussinesq model.

– Fluid body force equation:

thermal expansion coefficient, average temperature

  • Simulate impurity levels with a passive scalar.

– Passive scalar is carried (convected and diffused) by LAr similar to colored dye in water. – One‐way coupling: “passive” scalar does not affect the LAr motion.

  • Simplify cryostat FC and APA geometry using porous regions.

11/10/2017 3 Liquid Argon Flow CFD Simulations

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SLIDE 4

Impurity Level Quantification

  • Method 1: Electron Lifetime

– τ

∗

  • ∗
  • ∗
  • – Useful when exact value of the impurity surface flux is known.

– Can compare to experimental electron lifetime measurements from 35 Ton cryostat.

11/10/2017 4 Liquid Argon Flow CFD Simulations

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SLIDE 5

Impurity Level Quantification

  • Method 2: Normalized Percent Difference

– Impurity level scaled such that the average level within the field cage is 1 (or 100%). – Levels expressed as +/‐ % above or below 100%. – Useful when exact value of the impurity surface flux is unknown. – Easier to compare impurity levels between simulations.

11/10/2017 5 Liquid Argon Flow CFD Simulations

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SLIDE 6

Simulations to Date

  • 35 Ton
  • V1 Design

– Full and symmetric models

  • V2 Design

– Symmetric only

  • Latest Design

– Full and symmetric – Various operating conditions

  • ProtoDUNE

11/10/2017 6 Liquid Argon Flow CFD Simulations Top View of Latest Design Removed in Symmetric Models

. .

35 Ton ProtoDUNE

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35 Ton Simulation

  • Red: heat enters through wall
  • Blue: constant temperature,

constant impurity flux

  • Yellow: field cage is a 23%

porous wall

  • 9.5 GPM LAr flow rate
  • Constant inlet temperature:

87.808 K

7 Liquid Argon Flow CFD Simulations 11/10/2017

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SLIDE 8

35 Ton Simulation

8 Liquid Argon Flow CFD Simulations

Impurity Distribution Fermilab Results

(Erik Voirin, Fermilab)

11/10/2017

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SLIDE 9

35 Ton Simulation

9 Liquid Argon Flow CFD Simulations

4 purity monitors in this corner

(Geometry Not accounted for in CFD model)

(Erik Voirin, Fermilab)

11/10/2017

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SLIDE 10

35 Ton Simulation

10 Liquid Argon Flow CFD Simulations

2500 3000 3500 4000 4500 5000 5500 6000 0.5 1 1.5 2 2.5

Electron LIfetime [μs] Elevation from Cryostat Floor [m]

SDSU Simulation Fermilab Simulation ‐ Probe 1 Fermilab Simulation ‐ Probe 2 Fermilab Simulation ‐ Probe 3 Experimental

11/10/2017

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SLIDE 11

35 Ton Simulation

  • Simulation agrees with experimental data.
  • Can apply same CFD methods to other designs.

11/10/2017 11 Liquid Argon Flow CFD Simulations

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LBNF Cryostat ‐ Geometry

11/10/2017 12 Liquid Argon Flow CFD Simulations

  • APA – approx. 80% open
  • CPA – impermeable
  • Field Cage – 23% open

Field Cage Field Cage APA APA APA CPA CPA

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LBNF Cryostat ‐ Geometry

11/10/2017 13 Liquid Argon Flow CFD Simulations

Field Cage Field Cage Field Cage Field Cage Cross Section from Side View

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LBNF Cryostat – Boundary Conditions

  • Top Wall (LAr surface):

– LAr Saturation Temperature: 88.348 K – Passive Scalar Flux: 1

  • Remaining Exterior Walls:

– Heat Flux: 7.2 W/m^2

  • Electronics Surfaces:

– Total Heat Source: 23,700 W

  • Inlet Temperature:

– Maintained at 0.4418 K above outlet temperature to account for pump work – Flow rate in table on the right

  • APA and FC Planes:

– Treated as Porous Region, see next slide

V1 Full V1 Sym. Latest Sym. Inlet Flow Rate 4 Pumps 4 (2) Pumps 1 (0.5) pump # of Inlets 1 1 (0.5) 12 (6) # of Outlets 4 4 (2) 7 (7)

14 Liquid Argon Flow CFD Simulations 11/10/2017

Single Pump = 103 GPM Electronics Surfaces in pink

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Representing APA Plane with Porous Region

The APA planes consisted of 10 layers:

  • Plane 1: Vertical wires (150 micron

diameter at a 5‐mm pitch)

  • Plane 2: +60° wires
  • Plane 3: ‐60° wires
  • Plane 4: Vertical wires
  • Plane 5: Mesh 80% open (90° wires
  • f 0.528‐mm dia. and 5‐mm pitch)
  • Planes 6‐10: Symmetry of planes 1‐

5, with a 75 mm space between planes 5 and 6.

15 Liquid Argon Flow CFD Simulations 11/10/2017

1 2 3 4 5

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Representing APA Plane with Porous Region

  • Motivation: Cells required to

represent real APA geometry for entire cryostat is vastly beyond computational resources.

  • Mimic the flow resistance on the

macro‐scale using porous regions.

– Simulate only a small section of real APA plane geometry. – Find pressure drop across planes at several velocities in expected range.

16 Liquid Argon Flow CFD Simulations 11/10/2017

Inlet Outlet Symmetry on 3 sides APA Mesh Layers

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Representing APA Plane with Porous Region

  • Plot pressure vs. velocity.
  • Determine quadratic trend line.
  • Use coefficients as inertial () and

viscous () flow resistance coefficients.

  • Divide coefficient by porous region

thickness.

  • Final APA resistance coefficients:

– Inertial: 11,300 kg/m^4 – Viscous: 119 kg/m^3‐s

17 Liquid Argon Flow CFD Simulations 11/10/2017 y = 563.21x2 + 5.9315x R² = 0.9999

0.2 0.4 0.6 0.8 1 1.2 0.01 0.02 0.03 0.04

Pressure Drop [Pa] Velocity [m/s] Fermilab Simulation SDSU Simulation

  • Poly. (SDSU Simulation)
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Representing FC Plane with Porous Region

  • FC plane consist of 23% open,

slot geometry, assumed 23 mm slot at 100 mm pitch.

  • Used same method as APA plane

to find resistance coefficients.

  • Final resistance coefficients:

– Inertial: 411,000 kg/m^4 – Viscous: 247 kg/m^3‐s

18 Liquid Argon Flow CFD Simulations 11/10/2017

Inlet Outlet Symmetry on all four sides 2.3 cm slot

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LBNF V1: Impurity and Temperature at z = 30.5 m plane (pump discharge)

11/10/2017 19 Liquid Argon Flow CFD Simulations

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LBNF V1: Impurity and Temperature at z = 0 m plane (center of cryostat)

11/10/2017 20 Liquid Argon Flow CFD Simulations

z = 0 m plane (center of cryostat)

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Simulations

  • Latest Configuration:

– Symmetric: standard operating conditions, electronics turned off, and half LAr flow rate. – Running full model: Erik Voirin’s results showed significant asymmetry.

11/10/2017 21 Liquid Argon Flow CFD Simulations

Top View of Latest Configuration Removed in Symmetric Models

. .

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Mesh Validation

  • Used two mesh types with varying

levels of refinement.

  • Solutions have been in agreement.
  • Polyhedral mesh requires more

iterations and time (about 30%) to solve the passive scalar for impurity distribution.

  • Currently using trimmed cell mesh

(hexahedral, cubes of varying sizes).

22 Liquid Argon Flow CFD Simulations 11/10/2017

Polyhedral Trimmed

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Latest Design: Symmetric vs. Full Model

  • Simulating half the cryostat will

cut calculation time in half.

  • Must determine if both full and

symmetric models yield similar results.

23 Liquid Argon Flow CFD Simulations 11/10/2017

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  • Sym. vs. Full: Temperature at Z = 5.17 m

In Line with Inlet

24 Liquid Argon Flow CFD Simulations 11/10/2017

Full Symmetric

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  • Sym. vs. Full: Impurity at Z = 5.17 m

In Line with Inlet

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Full Symmetric

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  • Sym. vs. Full: Temperature at X = 3 m

26 Liquid Argon Flow CFD Simulations 11/10/2017

Full Symmetric

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  • Sym. vs. Full: Impurity at X = 3 m

27 Liquid Argon Flow CFD Simulations 11/10/2017

Full Symmetric

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Electronics Turned Off

  • Heat flux on electronics changed

from 23,700.0 W to 0.0 W.

  • No other changes.
  • Will compare impurity level

minimum, maximum, and standard deviation after slides of images.

28 Liquid Argon Flow CFD Simulations 11/10/2017

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Electronics Off: Temperature at Z = 5.17 m In Line with Inlet

29 Liquid Argon Flow CFD Simulations 11/10/2017

Electronics On Electronics Off

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Electronics Off: Impurity at Z = 5.17 m In Line with Inlet

30 Liquid Argon Flow CFD Simulations 11/10/2017

Electronics On Electronics Off

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Electronics Off: Temperature at X = 3 m

31 Liquid Argon Flow CFD Simulations 11/10/2017

Electronics On Electronics Off

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Electronics Off: Impurity at X = 3 m

32 Liquid Argon Flow CFD Simulations 11/10/2017

Electronics On Electronics Off

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Half Flow Rate

  • LAr inlet flow rate changed from

103 GPM to 51.5 GPM

33 Liquid Argon Flow CFD Simulations 11/10/2017

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Half Flow Rate: Temperature at Z = 5.17 m In Line with Inlet

34 Liquid Argon Flow CFD Simulations 11/10/2017

Regular Flow Rate Half Flow Rate

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Half Flow Rate: Impurity at Z = 5.17 m In Line with Inlet

35 Liquid Argon Flow CFD Simulations 11/10/2017

Regular Flow Rate Half Flow Rate

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Half Flow Rate: Impurity at X = 3 m

36 Liquid Argon Flow CFD Simulations 11/10/2017

Regular Flow Rate Half Flow Rate

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Half Flow Rate: Temperature at X = 3 m

37 Liquid Argon Flow CFD Simulations 11/10/2017

Regular Flow Rate Half Flow Rate

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No CPA Planes

  • Simulation mesh was adjusted to

remove prism layers on CPA plane surface

  • CPA plane was changed from

solid (impermeable) region to fluid region.

38 Liquid Argon Flow CFD Simulations 11/10/2017

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Without CPA: Temperature at Z = 5.17 m In Line with Inlet

39 Liquid Argon Flow CFD Simulations 11/10/2017

With CPA Plane Without CPA Plane

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Without CPA : Impurity at Z = 5.17 m In Line with Inlet

40 Liquid Argon Flow CFD Simulations 11/10/2017

With CPA Plane Without CPA Plane

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Without CPA : Temperature at X = 3 m

41 Liquid Argon Flow CFD Simulations 11/10/2017

With CPA Plane Without CPA Plane

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Without CPA : Impurity at X = 3 m

42 Liquid Argon Flow CFD Simulations 11/10/2017

With CPA Plane Without CPA Plane

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No Inlet Heat Addition

  • Inlet temperature set to be equal

to outlet temperature.

  • LAr will not rise as quickly since it

will be colder than previous simulations.

43 Liquid Argon Flow CFD Simulations 11/10/2017

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No Inlet Heat Addition: Temperature at Z = 5.17 m In Line with Inlet

44 Liquid Argon Flow CFD Simulations 11/10/2017

Standard Without Inlet Heat Rise

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No Inlet Heat Addition: Impurity at Z = 5.17 m In Line with Inlet

45 Liquid Argon Flow CFD Simulations 11/10/2017

Standard Without Inlet Heat Rise

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No Inlet Heat Addition: Temperature at X = 3 m

46 Liquid Argon Flow CFD Simulations 11/10/2017

Standard Without Inlet Heat Rise

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No Inlet Heat Addition: Impurity at X = 3 m

47 Liquid Argon Flow CFD Simulations 11/10/2017

Standard Without Inlet Heat Rise

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Field Cage Impurity Values: scaled so that the average impurity in the field cage is equal to 1. Table lists percent above/below average.

Latest Design: Field Cage Impurity Range Information

  • Turning off the electronics does not significantly affect the scaled

min/max or standard deviation.

  • Half LAr recirculation rate decreases the max value and standard

deviation

48 Liquid Argon Flow CFD Simulations 11/10/2017

V1 Design Poly New Poly Trimmed Full Trimmed No Elec Half Flow No CPA No Inlet Heat Max Value 7.90% 2.13% 1.27% 1.34% 1.21% 1.51% 0.71% 1.30% 1.24% Min Value

  • 11.80%
  • 4.76%
  • 4.30%
  • 5.93%
  • 4.86%
  • 4.24%
  • 3.20%
  • 5.39%
  • 7.31%

Standard Dev. 1.63E-02 1.41E-03 1.38E-03 1.72E-03 1.61E-03 1.70E-03 1.04E-03 1.45E-03 2.68E-03

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ProtoDUNE

49 Liquid Argon Flow CFD Simulations 11/10/2017

Boundary Conditions Top Wall LAr Saturation Temperature: 87.93 K Passive Scalar Flux: 1.0 Other Exterior Walls Heat Flux: 5.76 W/m^2 Inlet 19 GPM flow rate split across 4 inlets 0.4418 K above outlet temperature Outlet Single outlet CPA planes Impermeable stainless steel APA planes Same as previous. Field Cage planes Same as previous. Ground plane Porosity: 10% open Inertial Resistance: 2.373e7 kg/m^4 Viscous Resistance: 4007 kg/m^3-s

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ProtoDUNE

Z Cross Section View X Cross Section View

50 Liquid Argon Flow CFD Simulations 11/10/2017

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ProtoDUNE: Streamlines

51 Liquid Argon Flow CFD Simulations 11/10/2017

View from +Z direction

View from ‐Z direction

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ProtoDUNE: Impurity and Temperature at x = 0.0 m (center of cryostat)

52 Liquid Argon Flow CFD Simulations 11/10/2017

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ProtoDUNE: Impurity and Temperature at z = 0.4 m (Through CPA Plane)

53 Liquid Argon Flow CFD Simulations 11/10/2017