Conjugate Heat Transfer Analysis on a graphics card.
Aim: To perform a steady-state conjugate heat transfer analysis on a model of a graphics card.
Software used: Ansys 2020 R1
Objectives:
- Run the simulation by varying the velocity from 1m/sec to 5m/sec for at least 3 velocities and discuss the results.
- Find out the maximum temperature and heat transfer coefficient attained by the processor.
- Prove that the simulation has achieved convergence with appropriate images and plots.
- Identify potential hotspots on the model.
CHT Analysis:
The analysis was performed in two different cases:
(1) Coarse mesh or baseline mesh
(2) Fine mesh
According to the variation in velocities, simulations were done.
Graphics card contains three important parts: fins, base(PCB board) and processor.
Here, the fin is made up of Aluminium, the base was made up of Copper and the processor was made up of gold.
Material Properties:
| Materials | Density(Kg/m^3) | Specific Heat Cp (j/Kg-K) | Thermal Conductivity (W/m-k) |
| Aluminium(Al) | 2719 | 871 | 202.4 |
| Copper (Cu) | 8978 | 381 | 387.6 |
| Gold (Au) | 19320 | 129.4 | 297.73 |
Set up:
The steady, pressure-based and absolute solver was used.
Energy equation was used.
Model: Standard K-epsilon model with standard wall functions.
Fluid: Air
Solids: Aluminium, copper and gold
We have taken three velocities such as 1 m/s, 3 m/s and 5 m/s.
Temperature is set at 300K.
Power used by the processor is 10 W.
So heat generated by the processor is 156250000 W/m^3
Geometry:
COARSE MESH:
Meshing-
Element Size: 10 mm
No. of nodes: 16059
No. of Elements: 85361
Residual:
Velocity Contour:
Velocity here was 5m/s
Temperature Contour:
From this, we can see the highest temperature is 356.49K.
Heat Transfer Coefficient:
Max wall heat transfer Coefficient = 1149.27 W m^-2 K^-1
FINE MESH:
Element Size: 5 mm
No. of Nodes: 88554
No. of Elements: 506299
Mesh Closeup:
(a) Velocity at 1 m/s:
Residual-
Solution Converged:
Velocity Contour:
Temperature Contour:
Here Max temperature attained is 419.44K
HTC:
Max HTC attained: 1141.85 W m^-2 K^-1
Volume Rendering:
Velocity Vectors:
(b) 3 m/s
Residual:
Solution Converged:
Velocity Contour:
Temperature Contour:
Max temperature attained: 356.34 K
HTC:
Max HTC attained: 1141.85 W m^-2 K^-1
Volume Rendering:
Velocity Vectors:
(c) 5 m/s
Residual:
Solution Converged:
Velocity Contour:
Temperature Contour:
Max Temp attained: 341.53 K
HTC:
Max HTC attained: 1141.85 W m^-2 K^-1
Volume Rendering:
Velocity Vectors:
Observation-
For Coarse mesh:
| NO | VELOCITY (m/s) | MAX TEMPERATURE ATTAINED (K) |
| 1 | 5 | 356.49 |
Max HTC attained: 1149.27 W m^-2 K^-1
For Fine mesh:
| NO | VELOCITY (m/s) | MAX TEMPERATURE ATTAINED (K) |
| 1 | 1 | 419.44 |
| 2 | 3 | 356.34 |
| 3 | 5 | 341.53 |
Max HTC attained: 1141.85 W m^-2 K^-1
CONCLUSION:
1. Fine mesh used in graphics card is more efficient than in coarse mesh. As we can see that in coarse mesh, at 5 m/s maximum temperature attained is 356.49K but in finer mesh, we can see that at 3 m/s maximum temperature attained is 356.34 K.
2. On comparing the velocities we can see that as the velocity of the fluid air is increasing maximum attained temperature starts to decrease.
3. Potential hotspot in the graphics card was the processor as the main heat source in the graphic card is the processor only.