COMPUTER MODELING OF FLUID STRUCTURE HEAT TRANSFER

SOFTWARE fluidyn - MP

PRESENTATION OF fluidyn - MP

General : role & utility of Computational Fluid DynamicsA reliable numerical representation of a real processus with the help of well adapted physical models

Easy to use & adapted to optimisation studies in industrial processes

Economic with a security advantage

Ideal complementary tool for experimental measurements

Access to physical variables (velocities, pressure, temperature, etc.) at each point in the domain

Software fluidyn - MP, CHT Model Strong coupling & conjugate heat transfer between fluid & structures integrated in a single software platform

Robust physical models & various well adapted solvers

Finite Volume Method for fluids and Finte elements method for structures

Automatic exchange of boundary conditions between fluids & structures - Adaptative Fluid Mesh

Local time step used to reduce CPU time

3-DimensionsCompressible / incompressibleMechanical / thermal shocks Viscous / non-viscousLaminar / turbulentMulti-speciesMulti-phaseSolution of Navier-Stokes EquationsFluid Solver

Non-Newtonian Flows : Bingham lawPower law

Chemical combustion reactions Arrhenius modelEddy-break-up modelEddy dissipation model

Deflagration & fireBLEVEPool fire

DetonationJWL model

Two phase flows droplets, bubbles, particlesEuler-Lagrange Monte-Carlo, Free surface flow ( VOF method + CSF method)

Fluid Solver

Algebraic ModelsBaldwin- LomaxMixing Length :Van Driest dampingAbbott & BushnellCebeci- SmithSub grid scale model SGS Two equations transport (k - e) & RNGReynolds stress model (anisotropic turbulence) Turbulence ModelsFluid Solver

Perfect gasIdeal gasJWL (Jones - Wilkins - Lee) for explosionsLinear - polynomialUser definedEquations of StateTemperature functionsUser definedViscosity & Prandtl numberFluid Solver

Spatial discretization schemesExplicit: Van Leer Flux Vector Splitting Roe Flux Difference Splitting 3rd order Advection Upwind Splitting, HLLCSemi- implicit : Weighted Upwind Scheme QSOU 2nd order Implicit : Central Difference Scheme 3rd order Flux Limiter Scheme (Van Leer, SMART, etc.)

Fluid Solver

Explicit :Time stepglobal minimum for transient simulations local for steady state simulationsconvergence accelerationTemporal Integration 6 step 2nd order Runge Kutta.

Implicit:Gauss-Seidel or Jacobi iterative methodssteady state calculation & low velocities.Temporal discretization schemeFluid Solver

3 available models

Arrhenius Modelcoefficients of chemical reactions linked to Arrhenius parameters & activation temperatures

EDC Model (Eddy Dissipation Concept)Magnussen formula used to link the intermittent turbulent flame to the turbulent dissipation rate

Minimum of the Arrhenius model & EDCadapted to high velocity turbulent flows

Monitoring combustion gases (CO, CO2, NOX...) & smoke, dispersionCombustion Modelling

Finite Volumes computation in the fluid

Radiation ModelsTransparent MediaAutomatic calculation of 3D view factorsShadow effect of intermediate obstaclesOpaque Media Six-Flux modelDiscrete ordinate model

Collaboration with research laboratories (EM2C laboratory of Ecole Centrale, Paris) et industries (CIAT) for heat transfer modellingRadiation Modelling

Convectionfinite volumes computation in the fluidautomatic computation of heat transfer coefficient in fluid - structurehigh order spatial solution schemes (3rd order)

Conductionfinite elements computation in the structure (beams, shells, tetrahedrals, etc.)computation with an adapted local time step

Strong coupling with automatic exchange of boundaryconditions between fluid & structuresConvection / conduction modelling

Finite Elements beams shellstetrahedral, hexahedralbricks, springs, etc.

Material characteristics

Linear elasto-plastic, orthotropic Piecewise linear Non linear plasticStructured solver

Structured solver Small deformations & large displacements Finite Elements method

Large deformationsFinite Elements method

Finite Elements solversExplicit / implicit

Rayleigh damping

Boundary Conditions

Transient or constant

Outside :at nodes : temperature, forces, displacementsat faces: pressure, volume forces

Imposed automatically in fluids & structures

Modelling displacement of fluid mesh with Updated Lagrangian methodStructured Solver

Computation Procedure - 4 steps

Multi-block structured

Un-structuredDelaunay method2D & 3D meshesHybrid, tetrahedral or hexahedral mesh

Adaptative meshShocks, turbulent boundary layers, ..Refined mesh & automatic interpolation of the solution.

Interactive, simple & automatic

Complex geometries

MeshPre - processor

Geometry & computation parameters visualisation during simulation.

3D colour visualisation.

Multi-viewport facility : upto 30 viewports

Comparison of results obtained from different computations

Vectors, iso-contours, iso-surfaces & 3D current lines

Translations, rotations, multi projections

XY plots: residual & other parameters

AnimationsPost - processor

Examples of studies conducted with fluidyn - MPModelling of Fluid Structure Heat Transfers Fire in a traincompartmentExchanger slab (CIAT)RefrigeratorAfterburnerRiserWaste incineratorCooling metalPipe with 2 fluids (high pressure)

CASE 1Fire in a train compartment

Study FrameworkTwo phases :Simulation of code calibration in the case of fire modelling in an enclosure

experimental results : sample compartment consisting ofa seat & a ventilation system reproduction of heat phenomenon(convection + radiation) optimisation of principal parameters : smoke rates coefficient of smoke absorption distribution of chemical energy of the burned seat asradiative & convective energy mesh Simulation done for the whole car (complex geometry,Multiple boundary conditions)

Phase 1 : geometry

Phase 1 : Model setting

Phase 2 : geometry

Phase 2 : mesh

Phase 2 : Results

Phase 2 : Results

Phase 2 : Results

Phase 2 : ResultsVENTILATION & FIRE IN THE COMPLETE CARTemperature evolution in a compartment

Phase 2 : ResultsRoof

CASE 2Heat exchanges in a exchanger slab

Study frameworkDescription

Cooling in one of the fin tubes of an exchanger by air flow

Dimensions of the fin tube = 100 45 0.5 mm

Fin tube material = aluminium

Cooling fluid circulating in the tubes, T = 25C.

External temperature (air) = 10C.

Inlet air velocity = 2 m/s

Simulation until temperature stabilisation in the structure

Geometry

Mesh

ResultsMPpressure field

ResultsMPMPvelocities field

ResultsMPMP

ResultsMPtemperature field

ResultsMPtemperature in the structure

CASE 3Heat Exchanges in a refrigerator

Study frameworkDescription

The refrigerator has 4 compartments separated by 3 slabs cooled by a cooler (- 90C).Dimensions of the refrigerator = 128.5 55 74 cmThe compartments are interconnected behind the refrigerator.The refrigerator is insulated by a polyurethane layer.Insulator thickness : 8 mm cm on the panel in front, 12 cm in the restThe external temperature is 20C.The heat transfer across the insulation involves the natural convection currents in the compartments.Simulation time= 100 min (temperatures stabilised in the insulator & in the refrigerator)Air Polyurethane

= 1.972 kg/ m3 = 48.053 kg/ m3 = 1.23e-5 Pa.s k = 0.025 W/mK Cp = 1007.4 J/kgK Cp = 400 J/kgK Pr = 0.744 = 0.0055

Geometry

MeshTransverse View Top view

ResultsTemperature Contours in the insulator x = 0.45 m

ResultsTemperature Contours in the insulator y = 0.4 m

ResultsTemperature Contours in the insulator z = 0.75 m

ResultsNatural convection : velocity field x = 0.24 m

ResultsNatural convection : velocity field y = 0.53 m

ResultsTemperature contours in the compartments along X axis

ResultsTemperature contours in the compartments along Y axis

ResultsTemperature contours in the compartments along Z axis

CASE 4Heat exchanges in an afterburner

Description

Expansion of hot gases in the main body of an afterburner

Injection of cold air in the bypass duct which mixes with the hot air through the wall with holes.

Stabilisation of the turbulent flame by an arris gutter.

Liquid fuel injected across 4 surfaces.

Chracteristics : hot flows (combustion), heat transfers, structural deformations

Objectives : measurement of combustion efficiency (CO, CO2, H20)

Parameters : hot & cold air mixture, fuel vapor-gas mixture, stabilisation of the flameStudy framework

Geometry

Mesh

Numerical MethodsDescription

Twophase compressible flow, turbulent with kinetic reactions, jet, radiation

Unstructured mesh

High order schemes for solution of heat transfers

Steady implicit solver for the fluid & transient explicit solver for the structure

turbulence model RNG k e

combustion model EDC

fuel spray : discrete particle model, Monte Carlo size distribution

ResultsVelocity contours in the median plane

ResultsTemperature Contours in the median plane

ResultsHeat flux on the jacket of the cold air passage

ResultsPost combustion efficiency

ResultsDeformation of the after-burner flame holderInitial stateFinal state

ResultsResults of the displacements at the injector levels

ResultsDeformation at injectors levelInitial StateFinal State

CASE 5Heat transfers in a riser in maritime environment

Study frameworkDescription

The riser is a system composed of a vertical pipe consisting of a circulating fluid which is imbricated in an insulated matrix (chemical reactor). It is submerged in sea water.

Fluid = water circulating at an initial temperature of 45C

Vertical Pipe = steel

Insulator = gel, foam & polypropylene

Temperature of sea water = 4C

Stabilised temperatures during simulation = 7 h

Objective : establish a temperature map in the pipe & in the reactor

Geometry

ResultsTemperature contours in the fluid domain

ResultsTemperature contours in the structure

CASE 6Heat exchanges in a refractory of a domestic waste incinerator

Wall protected by the refractoriesHEAT EXCHANGER IN A DOMESTIC WASTE INCINERATOR

INCORPORER AutoCAD-r13

DESCRIPTION :The water / vapour pipes are inside the incinerator wall.The pipes are thermally protected by a refractory material (7 different insulators).insulatorrefractory Study framework

Mesh

TEMPERATURE CONTOURS T = 0 ms

TEMPERATURE CONTOURS T = 500 s

TEMPERATURE CONTOURS T = 1000 s

TEMPERATURE CONTOURS T = 2000 s

CASE 7Cooling in a piece of metal

METAL RETRACTIONTemperature contours in the metal

Mesh deformation Dynamic adaptative mesh which follows the retraction

CASE 8Nuclear applications : heat exchanges in a pipe under high pressure

Flow in a bend with heat transfer in the fluid & the pipe walls

Fluid : Incompressible = 870 kg/m3 = 0.001 Pa.s

Structure : Density = 7800 kg/m3Conductivity = 63W/m-K Specific Heat = 420

Inlet : Pressure = 157 bar Velocity = 1 m/s

cold fluid : Temperature = 423Kheat fluid :Temperature = 523K

Outlet : Pressure = 157 bar

HEAT TRANSFERS IN A PIPE

Geometry

Boundary ConditionsAccidental scenario in with 2 fluids present

Turbulent incompressible flowfluid = watermodel k- for turbulenceMultiblockModellingPipe = steelLinear elastic modelFinite elements = hexahedral

FLUIDSTRUCTURE

ResultsTemperature Contours in the fluid near the wall

ResultsTemperature contours in the wall

ResultsStress on the walls

ResultsPipe deformations under heat stress

ResultsVelocity field in the plane of the pipe diameter

CONCLUSIONThe software fluidyn - MP is well adapted to the modelling of strong heat coupling between the fluid & structure

The software fluidyn - MP is well adapted to the modelling of deformations (mechanical & heat in the structure)

Possibility to develop a software dedicated to the study of heat transfers between the bridge (structure) & the lacquer (fluide)automatic mesh generationstudy of different temperaturesadjustable & optimisable parameters(material choice, thickness)

UKSutton ColdfieldFRANCELyonCHINABeijingJAPANTokyo