KIT – Universität des Landes Baden-Württemberg undnationales Großforschungszentrum in der Helmholtz-Gemeinschaft

www.kit.edu

MODELLIERUNG VALIDIERUNG

Direct numericalsimulations(DNS)-TUD

RANS simulations

KIT-Univ.

u0

g q''

q''

Responsible: R. Stieglitz

LIMTECH A1: Thermo-hydraulic flow in a sudden expansion

� Motivation-Challenge-Aim� Infrastructure & preparatory work� Time planing

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A1: Thermo-hydraulic flow in a sudden expansion

Motivation

� in- and outflow of thermal storage containers,� heat exchanger bundles, � manifolds & collectors in PCS� highly heat loaded surfaces (CSP, ….) � Reliable CFD model badly needed

Challenges

� scale separation of thermal-viscous boundary layers� Different statistics of flow and thermal field� multi-scale flow structure � buoyancy � anisotropic turbulence� non-standard situation: liquid metal

Aim

� Reliable description of TH performance in different flow regimes � development of adequate numeric design tools

q

q

CSP reveiver

Receiver

collectormanifold

distributor

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FOCUS

� validity limits of model assumptions

� Model development & validation (anisotropy momentum, heat flux)for LM

Benchmark experiment

KIT

Direct numerical

simulations (DNS)-

TUD

RANS

Simulations

KIT-Univ.

A1: Thermo-hydraulic flow in a sudden expansion

T=const.

Trifold strategy�Benchmark experiment in simple geometry ����backward facing step (BFS) �data

�RANS simulation (industrial approach)� anisotropic turbulence modelling

for industrial application� identification of limitations

�DNS simulation� reference data for RANS � transition regimes

(laminar � turbulent, buoyant � mixed � forced convection)

u0

a

u0

h

g q, T

q, T

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Work plan

� WP1: Preparatory Phase (all Partners)

� WP2: RANS simulations /modeling (KIT-FSM)

� WP3: DNS, LES, Hybrid modeling and simulations (TUD)

� WP4: Experiment @ KASOLA facility (KIT)

� WP5: Flow field analysis (all Partners)

Know how & role of Partners

� KIT KASOLA: Liquid metal know how, design & experiment (1 Sci.)

� KIT –FSM: RANS simulation& modeling (1 PhD)

� TUD: LES, DNS & Hybrid modeling & simulation (1 PhD)

Link to other subprojects

� Young investigator group for measurement techniques

� B1 (transitional flows), B2 (solar apps), B4 (PCS) and C3 (LIMMCAST)

A1: Thermo-hydraulic flow in a sudden expansion

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Prototypic Benchmark: Vertical Backward Facing Step

� stratification problem (buoyancy) at large axial ∆T

� flow separation at geometry discontinuities� challenging experiment with liquid metal

Approach

� Here small Pr-Fluid(PrSodium=0.007)

� LES u-Field

� + DNS of T-Field

Measurement

� Velocity - Pitot-tube

� Thermocouples

Conditions:

Re=104, T =310°C=const,Tin=260°C

a=60mm, l=50a, h=1/4a

aa

u0

h

g q''

q''

A1: Thermo-hydraulic flow in a sudden expansion

T=const.

u0

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KASOLA: Plant

Na-Air HX

Cold trap

Na tank

MHD pump

Solar storage tank H

~ 1

2 m

Expansion tank

Test pool

Versatile test circuit

R&D Focus

� liquid metal (LM) systems for transmutation

� Accelerator target development

� Studies of LM for solar applications

� Development of turbulent LM heattransfer models for CFD tools

KEY DATA

� Heating power: ~ 800 kW

� Temperature range: 150°-550°C

� Maximum flow rate: 150 m3/h

� Sodium inventory : 7m3

� Tent. Start-up: 2/3 Quarter2013

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CURRENT STATUS

� Design, development & build-up of the KASOLA loop (Hering et al.)

� Components in house (purchased, manufactured)

� Loop concept certified by in principal technical survey

� Safety concept elaborated and safety report existent (to be completed in minor parts by the pre-requisites of the TÜV)

� Development of a KASOLA model with TRACE to estimate the required thermal load (Homann, Jäger)

� Hydraulic evaluation of KASOLA with numerical methods (Onea, Homann)

� Design, optimization of KASOLA components, e.g. cold trap, with CFD (Onea)

� Improvement of the system code TRACE for thermal-hydraulic investigations of Na flow (Jaeger)

SPECIFIC project related work

� Evaluation of preliminary isothermal tests in air strand (A1 -Jäger…..)

� Set-up of small loop (Na; In-Ga-Sn, B1) for preliminary investigations (W. Jaeger

+ Student),

KASOLA

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CURRENT STATUS- Simulation work

� DNS computations by TUD started

� Turbulent LM Heat transfer RANS-LES modelling at KIT (FSM/ISL) revisited

� Development of a turbulent Prandtl number approach Prt = f(y+, Re, Pr) for CFD (M. Boettcher)

� Evaluation of the instrumentation ( ongoing Jianu )

KASOLA

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PRELIMINARY WORK

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CFD-Simulation @TUD :backward-facing step

Spectral-Element & Fourier-Method

12.5 Mio nodes

electro-magneticactuator

1870 =HRe

laminar

inflow

)sin(),,( tzyxff L ω=

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� Momentum field

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no forcing sinusoidal forcing

� Momentum field

Simulation: Flow with forcing

� iso-surface = λ2 criterion

� color = stream-wise velocity

CFD-Simulation @TUD :backward-facing step

Result: � Use of actuator reduces separation

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Analysis of DNS-Data of a Poiseulle duct flow (Kawamura et. al.)

RANS-Model: HFM

Dimensionless quantities

CFD-Simulation @KIT : advanced turbulent heat flux modeling

� Temperature field

flow direction

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� Low Pr extension requires modified damping term of pressure dissipation

CFD-Simulation @KIT : advanced turbulent heat flux modeling

� Temperature field

© PhD Baumann 2012

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CFD-Simulation @KIT : advanced turbulent heat flux modeling

� Temperature field

© PhD Baumann 2012

LES: 6.4 Mio. CellsFine structure model: dyn. Smagorinksi-Model

DNS-Data of Chung, [2002]

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KASOLA model with TRACE p , dp distribution along the loop

KASOLA: Loop performance 1D modeling

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Isothermal Pre-testing of BFS-geometry

Idea1:1 representation of geometry, Re-analogyOptical access to flow field (u,u‘)Elaboration of critical measurementpositions complementary to CFD results

GoalOptimization of inflow conditioningGeometry optimizationWell defined CFD-boudary conditions L-STAR/SL

L-STAR/LLLDA

PIV / LIF

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Time frame and organisation

Preparatory phase

Erection of KASOLA

Air strand test

Optimizationgeometry

Built of test sectionfunctionality test

Advanced modelling

First LM Tests

Analysis and

Optimization

Extended campaigns

Activites to be shared by all

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