Week 6 - CHT Analysis on a Graphics card

Your Objectives:

1. Run the simulation by varying the velocity from 1m/sec to 5m/sec for at least 3 velocities and discuss the results.
2. Find out the maximum temperature and heat transfer coefficient attained by the processor.
3. Prove that the simulation has achieved convergence with appropriate images and plots.
4. Identify potential hotspots on the model.

 

INTRODUCTION 

Conjugate Heat Transfer (CHT) 

Conjugate heat transfer is defined as the heat transfer between two domains by exchange of thermal energy. For a system the thermal energy available is defined by its temperature and the movement of thermal energy is defined by its heat flux through the outer walls. Heat transfer in solids happens through conduction and walls by convection and in liquid phase through convection. 

CHT provides the temperature prediction and the hotspot regions at the solid-fluid interface, and we can also predict the heat transfer accurately for example- Conduction through solids, convection through fluid, and thermal radiation. It also provides the velocity and pressure distribution of fluid moving inside the solid. We can also use CHT in design optimization for improvement for heat transfer and cooling capacity. 

A video card (also called a graphics card, display card, graphics adapter, or display adapter) is an expansion card that generates a feed of output images to a display device (such as a computer monitor). Most video cards are not limited to a 6-inch simple output. Their integrated graphics processor can perform additional processing, removing this task from the central processor of the computer. 

 

 

SPACECLAIM GEOMERTY 

 

FINS 

PROCESSOR 

BASE 

Topology is set to share such that the data could be shared between the different components of the graphics card. 

 

 

Base Mesh 

A basic mesh is generated using the standard values recommended by Ansys. This mesh is used to obtain an initial solution which will help us to determine the location where mesh refinement is required. 

Element Order: Linear 

Element size: Default 

 

Simulation Setup 

Solver: Steady 

Type: Pressure Based 

Turbulence Model: k-Omega (SST) 

Materials: Different materials are used for each part, some of which are custom created 

Materials assigned are as follows: 

Base: Polystyrene 

Fins: aluminum 

Processor: Steel  

Enclosure is filled with Air. 

For Solid

 

 

Boundaries: 

• Inlet: 

              Type: Velocity Inlet 

              Velocity: 3m/s 

              Temperature: 300 K 

• Outlet: 

               Type: Pressure Outlet 

               Pressure: 0 Pa (Gauge Pressure) 

               Temperature: 300 K 

• Symmetry: Symmetry 
• Wall: Wall 

 

Cell Zone Conditions 

 

The processor is assumed as the only source of heat. The heat generated by the processor is calculated as: - 

Graphics Card Power = 2W 

Volume of the card = 8 x 8 x 1 

                            = `64mm^3=64e^-9m^3`

  

Heat Generated = `P/V=2/(64e^(−9))`

                    

                         = `31250000W/(m^3)`

Solution 

• Method: Standard 
• Number of Iterations: 500 

 

Simulation Output 

Residual

Temperature 

Heat Transfer coefficient 

Post Processing 

Global Hotspot Region 

Hotspot Around the Processor 

Wall Heat Transfer Coefficient 

Velocity Contour 

Temperature Contour 

 

 

REFINED MESH 

MESH 

Element Order: Linear 

Element size: 0.003 m 

Body Sizing (Fin) Element Size: 0.0005 m

Body Sizing (Processor) Element Size: 0.0005 m

Body Sizing (Base) Element Size: 0.003 m 

 

Velocity:  1 m/s

 

Simulation Output 

Residual

Temperature 

Heat Transfer coefficient 

 

Post Processing 

Global Hotspot Region

 

Hotspot Around the Processor 

Wall Heat Transfer Coefficient 

Velocity Contour 

Temperature Contour 

 

 

Velocity: 3 m/s

 

Simulation Output 

Residual

Temperature 

Heat Transfer coefficient 

 

Post Processing 

Global Hotspot Region 

Hotspot Around the Processor 

Wall Heat Transfer Coefficient 

Velocity Contour 

Temperature Contour 

 

Velocity:  5 m/s

 

Simulation Output

Residual

Temperature 

Heat Transfer coefficient 

 

Post Processing 

Global Hotspot Region 

Hotspot Around the Processor 

Wall Heat Transfer Coefficient 

Velocity Contour 

Temperature Contour 

 

 

RESULTS 

Velocity	The temperature at Processor [k]	The temperature at Fins [k]	HTC at Fins [Wm2kWm2k]
1	364.18	359.49	149.94
3	338.78	329.43	154.98
5	328.95	321.91	161.42

  

CONCLUSION 

As the number of elements increases the accurate results of temperature distribution is obtained 

From the above table, it is notable that, the net temperature of components of graphics cards decreases with an increase in inlet velocity. 

Hence it can be inferred that a higher inlet velocity results in better cooling and lower the average temperature thus keeping the components safe from damage. 

Furthermore, it can be observed that the temperature of components increases as the inlet velocity decreases from 5 m/s to 1m/s, also proving that higher velocity results in better cooling. 

From this we can conclude that , As Inlet velocity get increased --->Heat generated get decreased.