CONJUGATE HEAT TRANSFER ANALYSIS ON A GRAPHICS CARD
CONJUGATE HEAT TRANSFER
This type of heat transfer corresponds to the combination of the heat transfer in solids and heat transfer in fluids. Heat transfer in solid called as conduction and heat transfer in fluid called convection.
Conduction occurs due to the direct molecular collision. The faster kinetic energy collides with the low-speed kinetic energy and the heat transfer occur.
Convection process is not happed alone. It combined with the conduction or radiation. (CONDUCTION + ADVECTION=CONVECTION).
So, the Conjugate heat transfer occurred mostly in the cooling process like HEAT SINK, BATTERY COOLING, AIRFLOW OVER THE SOLID OBJECT FOR COOLING.
Whenever the solid and fluid interface appears, this type of CHT analysis can be done to find the optimum result by using the Ansys. It allows the simulation of the heat transfer between solid and fluid domains by exchanging the thermal energy at the interface between them.
CONJUGATE HEAT TRANSFER ON A GRAPHICS CARD:
The above diagram shows the geometry od the graphics card and the enclosure.In graphics card, processor is the main component which generate the heat source. Here graphics card are the solid object which generate the heat and this heat can be removed by allowing the air flow over the body. By the convection process heat is carried away from the graphics card.
Here encosure is the control volume where the graphics card kept inside and this simulation is similar to the ahmed body simulation except that heat source is added.
The components of the graphics card are:
A-Fins
B-Processor
C-PCB
Here processor generate the heat where the heat is conducted to the PCB. Fins are used for cooling process with the help of the fins areas that are covered by the air flow.
In the 1st case i am using the baseline mesh.
For the baseline mesh, here we are giving the element size as 10mm, where there is no capturing thr proximity.
It is possible for the formation of unstructured mesh which gives the result not accurate.
For that using the share topology option for the two bodies which result in formation of the structured mesh. The below diagram shows the formation of structured mesh.
For that two bodies there is no discontinuity in the meshing which shows that the mesh are generated as structured mesh.
Solving:
For the graphics we are using the different materials, such as ALUMINIUM,COPPER and GOLD
Fins-Aluminium
Processor- GOLD.
PCB-COPPER.
The above material properties are used for that materials respectively.
Heat Source:
Here I assume that processor produce the heat of 10W. So the heat generation produced by the processor is 1.5E8 w/m^3.
The above figure shows the heat source added for the processor.
Simulation is run for steady state analysis with the viscous k-epsilon model and energy is activated.
Air flow at inlet is 10m/s and the temperature of 300k.
The temperature contour for the graphics card it show that the maximum temperature obtained by the processor is 338k.
From the residual diagram it shows that the solution is converged around 200 iteration.
The above figure are shown as CFD post for Temperature, Wall heat transfer and the velocity contour by the plane respectively.
The area where Low Heat transfer coefficient might have a thermal damage on the field.
So for that this simulation is used to find the area of recirculation region which used to avoid to place the equipment.
Case 2:
Fine mesh- 56mm here I use to set the proximity capture and automatic method is used.
Elements-503668
The above meshing is the fine mesh where proximity capture is on.
Here the maximum temperature obtained by the processor is 325K.
The figure are shows the result for the fine mesh which the results are more accurate than the previous mesh.
COMPARISION
BASELINE MESH : max temp by processor-338k
FINE MESH : Max temp by processor-325K
From the heat transfer coefficient we founf the potential hotspot places where the heat transfer coefficient is low.
In that low HTC, recirculation is achieved which affect the thermal behaviour of the component.