Week 6 - CHT Analysis on a Graphics card

Aim: To perform a steady state conjugate heat transfer analysis on a model of Graphics Card.

Introduction:

• The term conjugate heat transfer (CHT) describes the process which involves variation of temperature within solids and fluids, due to thermal interaction between the solids and fluids, the exchange of thermal energy between the two physical bodies is called study of heat transfer, the rate of transferred heat is directly proportional to the temperature difference between the bodies.
• Conjugate heat transfer corresponds with the combination of heat transfer in solid and heat transfer in fluids, in solids, conduction often dominates whereas in fluids, convection usually dominates. efficiently combining heat transfer in fluids and solids is key to designing effective coolers, heaters or heat exchanger. forced convection is the most common way to achieve high heat transfer rate. in some applications the performances are further improved by combining convection with phase change.
• Heat transfer in solids and heat transfer in fluids are combined in the majority of applications. this is because fluids flow around solids or between solid walls and because solids are usually immersed in a fluid.

Graphic card

• A graphics card (also called a video card, display card, graphics adapter, VGA card/VGA, video adapter, display adapter, or mistakenly GPU) is an expansion card which generates a feed of output images to a display device, such as a computer monitor. Graphics cards are sometimes called discrete or dedicated graphics cards to emphasize their distinction to integrated graphics.

After importing the geometry we have to share the topology where we have to the do the confirmal meshing. Create shared topology, to avoid overlapping of mesh pattern at different regions of domain.

Now, the second phase of this project is to go the meshing and apply the name to the different parts of the components for Boundary Conditions.

Baseline mesh:

Refined mesh:

Mesh of fins and processor:

After applying the naming for the material and boundary conditions

Fluent setup:

General setup:

• Solver type: pressure based
• velocity formulation: absolute
• Time: steady state

Materials

• Copy solid materials from fluent data base.

Silicon:

Polysterene (Board):

Heat generated rate =Q/Volume

Let us assume Q=1 watt

Volume of the processor = 64mm^3

Heat Generated rate = 15625000 w/m^3

Create surface report definations for heat transfer cofficient , temperature averages:

Heat transfer cofficient:

Temperature average:

Temperature average of fins:

• Initialize
• hybrid initialization.
• Run calculation.

RESULTS:

Residual plot:

Heat transfer coefficient:

Temperature average:

Temperature average of fins:

Contour of graphic card with temperature:

Contour of the graphic card when it is enclosed: we can observe the flow flowing form right direction to left direction as form right side it is inlet and form left sode it outlet.

The velocity contour with temperature in it: As the fluid flows form inlet to outlet the temperaure of air gets increased due the presence of heat in the graphic card.

Case 2: Velocity with 3m/s

In this case we are taking the inlet velocity as 3 m/s and intializing it and the running for the calculations. It get converged at 69 iterations only as shown in the contour and residual below:

Residual plot:

Contour of graphic card with temperature:

Contour of the graphic card when it is enclosed: we can observe the flow flowing form right direction to left direction as form right side it is inlet and form left sode it outlet.

Case 3: Velocity with 5m/s

Inlet velocity magnitude = 5m/s

Residual plot:

Contour of graphic card with temperature:

Contour of the graphic card when it is enclosed: we can observe the flow flowing form right direction to left direction as form right side it is inlet and form left sode it outlet.

From the above 3 cases we can comapare the Heat Transfer coefficent and Maximum Temparature.

Inlet velocity (m/s)	Heat Transfer Coefficient	Avg-Temperature of processor(k)	Maximum Temperature
1	4.8477781	332.80854	332.93234
3	6.9632248	316.16386	316.27884
5	8.8864447	311.87464	311.98297

Conclusion:

1. The thermal performance is seen to get improved increasing velocity of air and refining the mesh more.
2. The maximum temperature of the processor is seen to decrease with the increase in velocity of air.
3. The convergence criteria are satisfactorily achieved for baseline and refined mesh setup.