Week 6 - CHT Analysis on a Graphics card

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

OBJECTIVE:

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.

THEORY AND EXPLANATION:

CONJUGATE HEAT TRANSFER(CHT) ANALYSIS:

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:

1. The maximum and minimum temperature in various parts of the system. eg: combustion chamber, gas turbines, chemical vessels, etc.

2. Temperature Distribution is related to the thermal stress over a particular wall or system etc.

3. 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.

4. A video card (also called a graphics card, display card, graphics adapter, or display adapter) is an expansion card which generates a feed of output images to a display devices (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.

CASE SETUP GEOMETRY:

1. Click on share topolygy option when we import the geometry.

2. Click on enclosure option.

3. A basic mesh is generated using the standard values to obtain the initial solution which help us to determine the loccation where the mesh refinement is required.

Mesh = 5mm

Body seizing for Fin and Base = 1mm

Processor = 0.5mm

ELEMENT QUALITY:

SIMULATION SETUP:

SOLVER: Steady

TYPE: Pressure based

TURBULANCE MODEL: K-Omega(SST)

MATERIALS:

1. FR-4:

2. ALUMINIUM:

3. SILICON:

4. AIR:

RESULTS:

1. Velocity-1m/s

RESIDUAL PLOT:

TEMPERATURE CONTOUR:

VELOCITY CONTOUR:

HEAT TRANSFER COEFFICIENT:

2. Velocity-3m/s

RESIDUAL PLOT:

TEMPERATURE CONTOUR:

VELOCITY CONTOUR:

HEAT TRANSFER COEFFICIENT:

3. Velocity-5m/s

RESIDUAL PLOT:

TEMPERATURE CONTOUR:

VELOCITY CONTOUR:

HEAT TRANSFER COEFFICIENT:

4. MAXIMUM TEMPERATURE:

Hotspot represents hottest part of chip. In our simulation processor is sole component which is generating so it will possess maximum temperature, so it is a hotspot.

CONCLUSION:

1. From the above table it is fairly notable that, the net temperature of componenets of graphics card decreases with increase in inlet velocity.

2. 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.

3. The simulation was performed to find affect of cooling fluid velocity on temperature rise of processor and base.it can be seen from graph that maximum temperature is reduced by 66K by just increasing air velocity by 2m/s and temperature further reduces by 14K if we use air velocity as 5m/s.