Heat  Transfer  Simula0ons  with  COMSOL  Mul0physics  

© 2012 COMSOL. COMSOL and COMSOL Multiphysics are registered trademarks of COMSOL AB. Capture the Concept, COMSOL Desktop, and LiveLink are trademarks of COMSOL AB. Other product or brand names are trademarks or registered trademarks of their respective holders.

Dr  Edmund  Dickinson  COMSOL  Ltd  

Agenda  •  Why  do  we  model  heat  transfer?  

•  Modeling  heat  transfer  with  COMSOL  Mul0physics®  –  conduc0on,  conduc0on  and  radia0on  –  Mul0physics:  electrical  hea0ng  –  Mul0physics:  cooling  flow  

•  Video  demo  –  Heat  transfer  in  a  light  bulb.  

•  How  to:  –  Try  COMSOL  Mul0physics  –  Contact  us  

•  Q&A  session  

Why  Do  We  Model?  

•  Concep0on  and  understanding.  

•  Design  and  op0miza0on.  

•  Tes0ng  and  verifica0on.  

Conjugate heat transfer simulation of an aluminum heat sink.

What  is  mul0physics?  

Mul0physics:  mul0ple  interac0ng  phenomena  

Could  be  simple:  

•  Heat  transfer  by  convec0on  in  a  fluid  flow.  

Could  be  complex:  

•  Reac0ng  flow  evolving  heat,  with  temperature-­‐dependent  reac0on  rates.  

Advantages  of  COMSOL  Mul0physics  

•  Mul,physics  –  Everything  can  link  to  everything.    •  Flexible  –  You  can  model  just  about  anything.  

•  Usable  –  You  can  keep  your  sanity  doing  it.  

•  Extensible  –  If  it’s  not  specifically  there…  add  it!  

                 Thermal Stress: A stator blade in the turbine stage of a jet engine is heated

by combustion gases, where the resulting temperature gradients introduce significant stresses. To prevent the stator from melting, air is passed through a cooling duct in the blade. Shown is the temperature distribution throughout the blade and in the flow stream.

All-­‐Inclusive  Interac0ve  Modeling  Environment  

Model  Builder  

Provides  instant  access  to  any  part  of  the  model  seZngs.  

•  CAD/Geometry  •  Materials  •  Physics  •  Mesh  •  Solve  •  Results  

Graphics  

Ultrafast  graphic  presenta0on,  stunning  visualiza0on,  and  mul0ple  plots.  

COMSOL  Desktop™  

Straigh_orward  to  use:  it  gives  full  insight  into  and  control  over  the  modeling  process.  

Product Suite  

Thermal  Analysis  

Conduc0on   Heat  transfer  of  moving  solids  

Convec0on  in  fluids   Radia0on  

Thermal  modeling  can  include  many  

different  effects.  

 

It  can  be  solved  for  both  steady  state  and  

0me-­‐dependent  problems.  

Thermal  Analysis:  Mul0physics  

•  Many  applica0ons  combine  heat  transfer  with  another  physics  type.  

•  Forced  /  natural  convec0on:    -­‐  fluid  flow.  

•  Joule  hea0ng:      -­‐  electrical  analysis.  

•  Thermal  stress:      -­‐  structural  analysis.  

Heat  Exchanger  –  Forced  Convec0on  

Flow  and  Heat    •  Model  of  a  heat  exchanger:  

–  Heat  conduc0on  in  solid  –  Heat  convec0on  in  air  flow  

•  60  °C  hot  stream  exchanges  heat  with  30  °C  cold  stream.  

•  Isotherms  show  temperature  distribu0on  through  the  steel  block.  

Natural  Convec0on  

•  Dynamic  heat  convec0on  caused  by  temperature  gradients.  

•  Occurs  when  density  depends  on  temperature.  

•  Control  complexity:  compare  empirical  models  with  a  complete  fluid  flow  model.  

 

Electronic  Component  Cooling  

•  Heat  sinks.  •  Circuit  board  components.  •  Can  include  modeling  of  the  cooling  flow.  

Natural  convec0ve  cooling  of  a  vacuum  flask  Coffee Temperature vs. Time

Temperature and velocity profile around a vacuum flask cooled by natural convection using low k-ε turbulence model

Light  Bulb  –  All  Forms  of  Heat  Transfer  in  One  Model  •  60  W    filament  heats  rapidly  over  the  first  seconds.  •  Induces  a  flow  driven  by  natural  convec0on.  •  Radia0on  is  significant  to  both  internal  and  external  heat  transfer.  

t = 0.1 s t = 60 s

Temperature Velocity

t = 0.1 s t = 60 s

Laser  Hea0ng  of  a  Spinning  Disc  

•  Gaussian  heat  pulse  for  laser  hea0ng  of  a  rota0ng  disc.  

•  Flexible  heat  transfer  condi0ons:  –  choose  site  and  intensity  of  

hea0ng.  –  directly  incorporate  physical  

complexity  such  as  a  rota0ng  solid.  

Laser  Hea0ng  –  with  depth  penetra0on  

Revolving Laser with Depth Penetration

•  Crea0ng  heat  from  other  physics.  •  Influence  of  temperature  change  on  physical  phenomena.  

Heat  Transfer:  Mul0physics  

Joule  Hea0ng  

•  Electrical  resistance  causes  power  losses  as  heat.  

•  Resis0ve  hea0ng  is  propor0onal  to  current  density.  

•  Joule  hea0ng  causes  thermal  expansion:  –  Deforma0on  and  stress  

from  a  mul0physics  model.  

Heat-­‐Induced  Deforma0ons  

•  Thermal  expansion  in  a  coil  changes  its  dimensions.  •  The  effect  of  deforma0on  on  the  inductance  can  be  

determined  using  a  mul0physics  model.  

Temperature

Deformation

Chemical  Reac0on  Modeling  

•  Thermal  decomposi0on  of  a  gas-­‐phase  species  in  a  flow.  •  High  ac0va0on  barrier.  

–  increased  temperature  accelerates  the  reac0on.  

Flow  Velocity    

Temperature    

Concentra,on  

Thermally  Induced  Creep  

•  Internally  pressurized  sphere.  •  Temperature  is  held  at  ~  40%  of  

mel0ng  point.  •  Mo0on  starts  aler  1000  hrs  (42  

days).  von Mises Stress

Stress at 3 points

Focused  Ultrasound  Hea0ng  

•  High-­‐Intensity  Focused  Ultrasound  (HIFU)  uses  sonic  energy  to  heat  damaged  or  diseased  0ssue.  

Sound Intensity (dB) Isotherms near focus after 1 second

Tissue

Water

Biohea0ng  –  Hepa0c  Tumor  Abla0on  

•  Low  frequency  Joule  hea0ng  using  a  catheter  inside  an  artery.  

•  Used  to  kill  cancerous  cells  in  a  tumor.  

•  Isotherms  allow  iden0fica0on  of  “damage”  region  where  cancer  cell  necrosis  occurs.  

Temperature

Voltage

RF  Hea0ng  –  Microwave  Oven  

•  Microwave  radia0on  in  a  box  heats  the  potato.  

•  Center  temperature  rises  quickly.  

Hea0ng  by  Internal  Fric0on  

•  Fluid-­‐structure  interac0on  (FSI)  in  the  cast  and  mold  for  an  aluminum  extrusion  process.  

•  Internal  fric0on  acts  as  a  heat  source.  

Viscosity changes in the non-Newtonian flow of

molten aluminum Isotherms and Flow Direction

von Mises Stress

Mold  Cooling  –  Mix  3D  Thermal  Modelling  with  1D  Pipe  Flow  

Mold  cooling  process  in  the  automo0ve  industry  

Pipe  Flow  Module  •  Fluid  flow  in  pipe  networks.  •  Heat  and  mass  transfer.  •  Couple  to  a  three-­‐

dimensional  heat  conduc0on  model.  

Cooling of a plastic mold of a steering wheel – including pipe flow in cooling channels.

EXAMPLE:    Light  Bulb  –  Heat  and  Flow  

•  Modeling  heat  transfer  in  a  60  W  glass  bulb  with  a  tungsten  filament  and  inert  argon  atmosphere.  

•  All  forms  of  heat  transfer!  

–  conduc0on  in  the  glass  –  internal  natural  convec0on  –  convec0ve  cooling  to  the  exterior  –  internal  surface-­‐to-­‐surface  radia0on  –  surface-­‐to-­‐ambient  radia0ve  loss    

Dr  John  Dunec  will  demonstrate  how  to  build  the  light  bulb  model  in  COMSOL  Mul0physics.  

John Dunec, Ph.D. COMSOL, Inc.

Upcoming  Workshops  North  America  

•  Los  Angeles,  CA  •  Arlington,  VA  •  Houston,  TX  •  Ouawa,  ON  •  Pasadena,  CA  •  Irvine,  CA  

Europe  

•  Oxford,  UK  •  Grenoble,  France  •  Paris,  France  •  Amsterdam,  Netherlands  •  Cardiff,  UK  •  London,  UK  •  GöZngen,  Germany  •  Stuugart,  Germany  •  Zürich,  Switzerland  •  Lund,  Sweden  

Register to our free hands-on workshops at:

www.comsol.com/events

Contact  Us  

•  www.comsol.com  –  User  Stories  –  Videos  –  Model  Gallery  –  Discussion  Forum  –  Blog  –  Product  News  

•  info@comsol.com  –  General  inquiries  

•  support@comsol.com  –  Technical  support  

Q&A  Session  

Any  ques0ons  not  answered  will  be  followed  up  by  email  

Product Suite  

www.comsol.com