Week 6 - CHT Analysis on a Graphics card

Aim:

Perform a steady-state conjugate heat transfer analysis on a model of a graphics card.

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.

Conjugate heat transfer:

Conjugate heat transfer is a type of heat transfer analysis between solids and fluid(s). This type of heat transfer includes both convection (between fluids) and conductive (between solids) heat transfer, as well as both forced and natural convection.

Graphics card:

A graphics card (also called a video card, display card, graphics adapter, GPU, VGA card/VGA, video adapter, or display adapter) is an expansion card which generates a feed of output images to a display device (such as a computer monitor).

Space claim geometry:

Mesh:

Initially we use base level mesh and refine the mesh based on the results of base level mesh.

No.of elements:182284.

Fluent setup:

Use steady state pressure based solver and K-omega SSt model.

Turn the energy equation on.And create materials for different parts of the graphics card.

1. Fins: use Aluminum as material for fins.

2.Base: Use FR4 as material for Base.

3.Processor: Use silicon for processor.

We need to change the materials in the cell zone conditions.

Setting up the source terms :

For this case we consider that, our processor is a source terms and it generating heat.

So, for setting up the source term go to Zones - Cell zones - and click on the processor for editing which is in the Solid.

After that select the material to gold and click on the source terms to enabled it and set the energy source to 1.

Then we initiate the solution with hybrid initialization for 200 iterations and select the tempearture contour and create solution animation for the contour.

Energy produced by the processor is 23437000 w/m^3.

Boundaries Condition:

Inlet

• Air is used as a fluid
• Velocity = 1 m/s
• Temperature = 300 K

Outlet

• Pressure = Gauge pressure (0 pa)

Results:

Case 1:

1. Baseline Mesh:

Inlet velocity= 1m/s

2. Mesh:

Main enclosure: 10 mm

Fins size: 2 mm

Processor: 2 mm

Base: 2 mm

Residuals:

velocity contour:

Wall heat transfer coefficient:

Global hotspot temperature:

Hotspot region around procesor:

Refined Mesh:

Enclosure = 3 mm

Fins = 0.5 mm (The capture curve is turned on.)

Base = 0.5 mm (The capture curve is turned on.)

Processor = 0.5 mm.

Total no. of elements in refined mesh = 731877.

Case 2:

Inlet velocity= 1m/s

Scaled residuals:

Velocity contour:

Wall heat transfer coefficient:

Global hotspot temperature:

Hotspot region around processor:

Case 3:

Inlet Velocity = 3 m/s

Scaled residuals:

Velocity contour:

Wall heat transfer coefficient:

Global hotspot temperature:

Hotspot region around processor:

Case 4:

Inlet Velocity = 5 m/s

Residuals:

Velocity contour:

Wall heat transfer coefficient:

Global hotspot temperature:

Hotspot region around processor:

Results:

Case	Mesh	Velocity	Heat transfer coefficient	Temperature
Case 1	Base mesh	1m/s	385.9	345.53
Case 2	Refined mesh	1m/s	1010.31	344.06
Case 3	Refined mesh	3m/s	1010.34	321.90
Caes 4	Refined mesh	5m/s	1010.31	316.01

Conclusion:

1. As the number of elements increase we get accurate results of the themperature distribution.

2.From the above table ,we can see that the temperature of graphics card decreases with increse in inlet velocity.

3.Thus higher the inlet velocity better cooling and temperature distribution on the graphics card.