CFD analysis of Conjugate Heat Transfer on a graphics card

CFD analysis of Conjugate Heat Transfer on a graphics card.

The conjugate heat transfer is the study when heat transfer is taking place from solid to fluid or vice versa. In this case, the heat transfer will take place from an electronics component to air through conduction first and then through forced convection. The material chosen for all the solid bodies is aluminum and for fluid an air. The specifications and methodology for both the mesh studies are:

Fluid Material - Air

Solid Material(Base, Processor, Fins) - Aluminium

Air Velocity - 1 m/sec

Heat Generation(Processor) - 2 X 10⁷ W/m²K

Viscous Model - SST K-ω Model

Solution Method - SIMPLE(Mostly 1st Order Upwind)

Baseline Mesh:

Baseline mesh is mesh where no refinement is done except the processor, where heat is getting generated. The automatic meshing was taking only 4 cells at the processor, so I added hexagonal sizing of 0.2 mm to make it little finer. The mesh is automatically getting finer at few sensitive areas and that is really important for capturing hot spots.

No. of Nodes- 53831

No. of Elements- 268080

Quality of mesh is not good, but it\'s working pretty well as far as the temperature hot spots are concerns.

The Solution is not converged well as the mesh is coarse, but momentum equation is converged and the solution is stable.

Velocity Profile:

The temperature profiles:

1. Base:

2. Fin Top

3. Processor:

4. Outlet:

Wall Heat Transfer Coefficient:

1. Base:

2. Fin Top:

Finer Mesh:

The finer mesh is meshing where some local setting has been done, but it\'s still not fine enough to give accurate result because of an academic license limit. The hexahedral mesh is used whenever possible to save a few elements for other crucial places. The results are different than before but whether those are close to accurate or not, can\'t be proven from the below analysis. All contours look smoother than before and wall and boundaries are well captured.

No. of Nodes - 95271

No. of Elements - 511375

Mesh definitely better than before as hot spots are well meshed and no. of elements also increased.

Quality is also better than previous mesh and it will definitely be useful for getting better results.

The same model is used for finer mesh and momentum and energy equations are converged. Continuity equation and the omega equation is taking time but the solution is surely stable.

Velocity Profile:

The temperature profiles:

1. Plane in the middle

2. Base:

3. Fin-top

4. Processor

5. Outlet

Wall Heat Transfer Coefficient:

1. Base

2. Fin-top

Observation:

1. Finer mesh improves the wall heat transfer coeffiecient, which decreases the maximum processor temperature.

2. The finer mesh is converging the energy equation way below the threshold set.

3. Hot-spot zone captured by both the mesh pretty well.

4. Above set-up definitely needs more than the above-studied number of elements to capture all things and to reach an accurate result.

5. As the wall heat transfer coefficient increased in finer mesh, processor temperature dropped and outlet temperature increased.

Sr. No.	Mesh	Max. Processor Temp.(0C)	Base Wall HTC(W/m2K)
1	Coarse	48.05	1346.81
2	Fine	45.39	1399.03