Week 6 - CHT Analysis on a Graphics card

CHT Analysis on a Graphics card

Conjugate Heat Transfer analysis is used for the processes that involve a variety of temperatures concerning solids and fluids, due to thermal interaction between them. A typical example would be the heating or cooling of a solid by the flow of air.

The exchange of heat between two bodies is known as heat transfer and the rate of heat transfer is directly proportional to the temperature difference between them. Heat transfer in solids is usually occurred by conduction whereas in the case of fluids heat transfer occurs by convection. Efficiently combining heat transfers between solids and fluids is the key to design effective coolers, heaters, or heat exchangers. Forced convection is the most common way to achieve higher heat transfers. For some applications, the performance is further improved by combining convection with phase change(for example liquid water to vapor phase change).

Heat transfers in solid and heat transfers in fluids are usually combined in the majority of the applications. This is because fluid flows around solids or between solid walls and usually solids are immersed in the fluids.

An accurate description of parameters such as material properties, flow regimes, geometry configurations, selecting correct models based on the physics to be captured, heat transfer modes near the boundaries is needed for the analysis of temperature fields and heat transfer.

Practical CHT problems are used to determine:

• The maximum and minimum temperature in various parts of the system. eg: combustion chamber, gas turbines, chemical vessels, etc.
• Temperature Distribution is related to the thermal stress over a particular wall or system etc.
• Temperature Response in time-dependent applications such as heating/cooling problem (For example, In the case of cooling a particular system such as engine cooling)
• Overall heat transfer co-efficient.

• STEP 1 : Geometry check & Topology sharing in Spaceclaim
• STEP 2 : Meshing
• STEP 3 : Physics Setup & Solving
• STEP 4 : Analysis using Post-processor

Geometry check & Topology sharing in Spaceclaim :

The below is a geometry which is a approximated modelled design of a graphics card.

Go to Workbench > Share > Topology will be shared

To check this, observe the geometry tree for indication of pink line on the PIDs

NOTE :

Topology has to shared for succesful transmission of information from one PID to other and for generation of conformal meshing

Meshing

Name the PIDs accordingly to setting up Cell Zone physics in Solver

Refining the Mesh for Processor through Bodysizing method

Results :

Physics Setup & Solving :

1.Solver: Steady

2.Type: Pressure Based

3.Turbulence Model: k-Omega(SST)

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

Reference Values :

Usually, the power consumed by a processor is converted into heat energy. To calculate the heat generated on the processor which is = Power consumed divided by the total volume of the processor

"The power consumption of today's graphics cards has increased a lot. The top models demand between 110 and 270 watts from the power supply; in fact, a powerful graphics card under full load requires as much power as the rest of the components of a PC system combined"

Taking this fact we will assume the power consumed to be 1W for study purposes

Heat generated = `frac{1}{64*10^-9}` W

Heat generated = 15625000 W

Boundary Conditions :

• Inlet - 1 m/s - 3m/s -5m/s
• Outlet - Pressure based outlet
• Symmetry Wall
• No wall treatment

Solution Method :

Results:

• Case 1 = 1 m/s
• Case 2 = 3 m/s
• Case 3 = 5 m/s

1. Residuals

2. Average Tempearture of Microprocessor

3. Average Heat Transfer co-efficient of Microprocessor Walls

4. Velocity Contour

4. Temperature Contour of Graphics Card

5. HTC Contour of Graphics Card

6. Recirculation region over Graphic Card Fins for Potential Hotspot

7. Potential Hotspots for Base and Microprocessor

Convergence & Data Comparions :