This document discusses best practices for conjugate heat transfer simulations in SimScale. It covers importing a CAD model, setting up simulations, and post-processing results. Key steps include cleaning up the CAD, assigning materials, setting boundary conditions like inlet velocity and chip power, and adding result probes. The example application is electronics cooling. Simulation results show airflow paths, temperature distributions, and validate the model has converged. Attendees are invited to ask questions.

1. CFD webinar
Conjugate Heat Transfer
Best Practices in SimScale

2. 1. Import your CAD model
2. Set up and define your simulation
3. Post-process your results
The SimScale Solution
How to use SimScale
3 Results & Post-Processing
2 Simulation Setup
1 CAD Upload

3. Today we will dive into conjugate heat transfer
best practices, looking at key setup
parameters, and how to judge the accuracy of
your results.
Today’s application
Conjugate Heat Transfer

4. What is...
Conjugate Heat Transfer?
● Heat transfer between solids and fluid(s)
● Both convection & conduction heat transfer
● Both forced and natural convection
● Common applications: electronics cooling, heat
exchangers, industrial machinery, some AEC, etc.

5. Simulation Setup
Conjugate heat transfer best practices
How to set up a conjugate heat transfer simulation in SimScale

6. CAD Cleanup
Geometry preparation
6
1. Electronics CAD is usually incredibly intricate
2. Large sections of electronics packages have little influence
over thermal performance; bus plugs, pin connectors, etc.
a. Should be simplified – rows of buses can be
approximated as a block
3. All chip pins, numbering imprints, serial numbers, fillets
should be removed
4. Small bodies which are not heat emitting should be
removed
5. Inlet/outlet extension should be added
6. Small fillets on heat sinks, capacitors, etc, should be
removed

7. Step 1
1. Drag & drop Parasolid CAD file to geometry
upload
2. Another option: directly import via Onshape
CAD Upload

8. Step 2
1. Open inner region
2. Imprint
Geometry Operations

9. Step 2
1. Open inner region
2. Imprint
Geometry Operations
Split Surface

10. 10
Step 3: Material Assignments
● Electronics chassis assigned aluminium
● Inlet, outlet extensions added
● Default aluminium assigned
Aluminium
Aluminium

11. 11
Step 3: Material Assignments
● Electrical connectors, snaps all assigned as
ABS
● These components are mostly simplified cubes
● Will have little thermal impact – flow
obstruction will impact thermal performance
ABS Plastic
ABS Plastic

12. 12
Step 3: Material Assignments
● All heat sinks were assigned copper
● Default copper from SimScale database
Copper
Copper

13. 13
Step 3: Material Assignments
● All capacitors, chips assigned as silicon
● Default silicon from SimScale database
Silicon
Silicon

14. 14
Step 3: Material Assignments
● Anisotropic thermal conductivity
● In plane: 22 W/m-K
● Through plane: 0.347 W/m-K
PCB
PCB

15. Step 4
● Inlets/outlets need to be defined
● Inlet: Velocity & Temperature
○ Pressure will be calculated
● Outlet: Pressure
○ Velocity, temperature will be
calculated
● Power sources
Boundary Conditions
Inlet: 2 m/s, 19 °C
Outlet: 0 Pressure Gauge

16. 5 Watts
1 Watt

17. Step 5
● Result control surface data probes should be
added to all areas of interest: inlet, outlet, heat
emitting bodies, etc.
● Result controls will plot field data (velocity,
pressure, temperature, etc.) as the run progresses
● Excellent method of judging convergence
● Simulation can be considered converged when
areas of interest stop fluctuating
Result Control
Inlet
Outlet

18. Step 5
● Result control surface data probes should be
added to all areas of interest: inlet, outlet, heat
emitting bodies, etc
● Result controls will plot field data (velocity,
pressure, temperature, etc) as run progresses
● Excellent method of judging convergence
● Simulation can be considered converged when
areas of interest stop fluctuating
Result Control
Chips

19. Results
Conjugate Heat Transfer Best Practices
Findings, ROI, key learnings, and next steps

20. ● Vector comets show flow path of air through
domain
● Recirculation of air in far back corner -
potentially warm section of model
● Bottom center area of model has low air flow
○ No large heat loads in that section
● Center of domain may be a “dead zone” due to
swirl
Results

21. ● Temperature plotted globally
● Capacitors are warmest parts of simulation
● Heat sinks are oversized
● Some heat sinks are not aligned with flow
direction
Results

22. ● High flow over heat sinks at entrance
● Heat sinks do an effective job of cooling
chips at entrance
● High velocity does not prevent high
temperatures on capacitors
● Low velocity in top left corner of domain
● Low velocity in bottom right of domain
● Fairly good flow in middle of model
Results

23. ● Streamlines show flow path of air through
domain
● Low flow air in far back corner - potentially
warm section of model
● Bottom center area of model has low air
flow
○ No large heat loads in that section
● Center of domain may be a “dead zone” due
to swirl
Results

24. Now, ask me anything.
Q&A
Conjugate Heat Transfer Best
Practices in SimScale
CFD webinar