Week 6 - CHT Analysis on a Graphics card
Objective:-
To perform CHT analysis on the graphics card.
Conjugate Heat Transfer (CHT) Analysis:-
The Conjugate Heat Transfer (CHT) analysis type allows for the simulation of heat transfer within solid and fluid domains by exchanging thermal energy at the interfaces between them.
Geometry:-
Geometry with Enclosure:-
Graphics Card Parts:-
Materials Assigned with their Properties:-
|
Aluminum (Pre-defined in fluent) (Fins & Other Components) |
Silicon ( User-defined) (Processor) |
FR-4 ( User-defined) (PCB) |
|
| Density (Kg/m^3) | 2719 /m^3 | 2000 Kg/m^3 | 1800 Kg/m^3 |
| Heat Capacity (J/Kg-K) | 871 J/Kg-K | 710 J/Kg-K | 950 J/Kg-K |
| Thermal Conductivity (W/m-K) | 202.4 W/m-K | 150 W/m-K | 0.29 W/m-K |
Mesh Generation:-
Base Mesh:-
Refined Mesh:-
Mesh Comparison:-
| Base Mesh | Refined Mesh | |
|
Enclosure |
4 mm | 2 mm |
|
Fins |
0.5 mm | 0.25 mm |
|
Processor |
0.5 mm | 0.25 mm |
|
PCB |
1 mm | 0.5 mm |
|
Other components |
0.5 mm | 0.25 mm |
|
Nodes |
152377 | 377552 |
|
Elements |
864546 | 2161327 |
Boundary Conditions:-
Generally, a Graphics Card processor consumes energy around 80 Watt, So taking 80 W as an input value. Hence, Heat generation in the processor is,
80/(0.04*0.04*0.002) = 2500000 W/m^3 .....(Taking half-area of processor)
Inlet:-
Velocity inlet with different velocities of 1m/s, 3m/s and 5m/s.
Temperature = 300k.
outlet:-
Pressure outlet.
Turbulence Model:-
K-omega SST turbulence model is used, as the k−ω SST model is best used for near-wall treatment and The k-ω SST model has relatively higher accuracy on predicting the heat transfer for the CHT simulation.
Results:-
Case-1:-
Base Mesh:-
Velocity = 1 m/s
Residual Plot:-
Average Temperature of Graphics Card:-
Temperature Contours:-
Velocity Streamline:-
Case-2:-
Refined Mesh:-
1.Velocity = 1 m/s
Residual Plot:-
Average Temperature of Graphics Card:-
Temperature Contours:-
Velocity Streamline:-
2.Velocity = 3 m/s
Residual Plot:-
Average Temperature of Graphics Card:-
Temperature Contours:-
Velocity Streamline:-
3.Velocity = 5 m/s
Residual Plot:-
Average Temperature of Graphics Card:-
Temperature Contours:-
Velocity Streamline:-
Result Comparison:-
| Velocity = 1 m/s | Velocity = 3 m/s | Velocity = 5 m/s | |
| Average Temperature | 51.25 C | 37.25 C | 33.75 C |
| Max. Temperature | 71.50 C | 49.6 C | 43.4 C |
| Max. Velocity | 1.33 m/s | 3.99 m/s | 6.57 m/s |
Conclusion:-
1. Refined mesh gives slightly accurate results in comparison to the base mesh.
2. At inlet velocity of 5m/s, Graphics card temperature is lowest, in comparison with velocity 3m/s and 1m/s.
3. As the plot of the average temperature of graphics card rises till around 100th iterations and then it remains stable till 500th iteration without any change, based on this we can conclude simulation has achieved convergence.
References:-
1. Influence of turbulence model parameter settings on conjugate heat transfer simulation. (Peng Wang • Yu Li • Zhengping Zou • Lei Wang • Songhe Song)