Week 6 - CHT Analysis on a Graphics card
Aim : CHT Analysis on graphics card
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:
- 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
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.
Power = 6w
Volume of the processer = 64mm^3
Heat generation = 6/64
= 93750000w/m^3
Plot and Contour
Base mesh size: 5mm
Refined processer mesh size : 2mm
Velocity : 1m/s
Residuals
Temperature plot
velocity plot
Tempearature contour
wall heat transfer contour
Processer contour
Fin base contour
Base contour
Base mesh size: 2mm
Refined processer mesh size : 1mm
Velocity : 1m/s
Residuals
Temperature plot
velocity plot
Tempearature contour
wall heat transfer contour
Processer contour
Fin base contour
Base contour
Base mesh size: 2mm
Refined processer mesh size : 1mm
Velocity : 3m/s
Residuals
Temperature plot
velocity plot
Tempearature contour
wall heat transfer contour
Base mesh size: 2mm
Refined processer mesh size : 1mm
Velocity : 5m/s
Residuals
Temperature plot
velocity plot
Tempearature contour
wall heat transfer contour
Processer contour
Fin base contour
Base contour
Result and Conclusion:
- Higher velocity in a particular region means a higher Reynolds number. That's why the heat transfer coefficient in that area is highest, which means the maximum amount of heat transfer is taking place from fluid to the solid in that region. This also results in a higher temperature of solid in that location.
- Heat transfer coefficient is a function of properties of the fluid at film temperature, temperature difference, temperature coefficient, buoyance force etc, hence mesh resolution near walls usually has the biggest impact on numerical results.
- For the turbulent models, we have to take care of the assumptions and the boundary conditions you put in the program. The mesh is a very important parameter to get nice results so we have to refine it in the important place of our drawing.
- Some factors that should be considered which the most significant is the turbulent boundary layer. If we are using any kind of low Reynolds turbulence model considering enhanced wall treatment (as your K-w SST model), so we need to make sure that we stay in the laminar sub-layer region where velocity profiles are assumed to be laminar and viscous stress dominates the wall shear which means Mesh/ grid dependency test is very important to get confidence over results.