Advanced CFD using ANSYS FLUENT-Conjugate Heat Transfer Analysis on a graphics card.
Introduction
In this project we will be running a conjugate heat transfer analysis on a model graphics card. the parametres we will be looking for are as follows:
1. The maximum temperature attained by the processor.
2. Prove that the simulation has achieved convergence with appropriate images and plots.
3. Find out the heat transfer coefficient at appropriate areas of the model.
4. Identify potential hotspots on the model.
We will be running the Simulation as two cases:
Case 1: Baseline mesh with 4mm element size
Case 2: Refined Mesh with 2mm element size for enclosure with 1mm sizing given for the graphics card components(Processor,Base and Fins)-Hex Dominant Method
Here special care was taken to further refine the area around the graphics card to ensure that the heat transfer can be mapped as accurately as possible keeping in mind the limitations of the academic version of ansys.
We can see from the meshes that both have shared topologies.
Procedure
Load the stp file in space claim. Run share option from workbench to create shared topology
Load the meshing module and apply meshing as required. Make sure that the element quality metric is upto scratch
Open the fluent module. Set inlet air velocity at 10m/s
Apply Different materials to the different components. Here I am using the processor material gold,the fins as copper and the rest of the graphics card as aluminium.
Apply an energy source for the processor. This option can be found in the option in cell boundary options and clicking on processor and turning on source. Here I am considering that the processor would be consuming around 50w of power. The processor has dimensions of 8*8*1. This results in w/m3 of 78125000000 w/m3.
Here the we will be using k epsilon visocous model.
Run the simulation till convergence is achieved.
Results
Case 1: Baseline Mesh-4mm element size
Convergence Proof
Temperature Contour
Heat Transfer Coefficient
Case 2: Refined Mesh-2mm element size and Body Sizing of 1mm for the Graphics Card Components
Convergence Proof
Temperature Contour
Heat Tranfer Coefficient
Results
The maximum temperature achieved was around 358 K at 50w TDP and an ambient temperature of 300k. The inlet air velocity was 10m/s.
The heat transfer coefficient was around 3.402 to 5.67 where the heat has to be dissipated.
The hot spots are present where the processor comes into contact with the fins.
The refined simulation has achieved convergence because the residuals indicate that the values are 1e-4 which is the minimum criteria, for the refined mesh.
The baseline case has all the residuals steadying out,which although not ideal is indicative of a loosely converged solution.
It is clear that the less refined case one is providing less than satisfactory results. It is providing inaccurate and crude contours of both temperature as well as heat transfer coefficient. It is also taking far longer to indicate any transfer of heat.