Week 6 - CHT Analysis on a Graphics card

Objective: To perform a steady state conjugate heat transfer analysis on a model of graphics card.

Introduction :
The term conjugate heat transfer (CHT) describes the process which involves variation of temperature within solids and fluids, due to thermal interaction between the solids and fluids, the exchange of thermal energy between the two physical bodies is called study of heat transfer, the rate of transferred heat is directly proportional to the temperature difference between the bodies.

Conjugate Heat Transfer (CHT) analysis :
Conjugate Heat Transfer analysis allows for the simulation of heat transfer between solid and fluid domains by exchanging thermal energy at the interfaces between them and transported via conduction within solids and adiditionally via convection within fluid domains.Conjugate heat transfer analysis can accurately predict heat transfer by simultaneous solving all the relevant solid and flow field heat transfer processes.Conjugate heat transfer corresponds with the combination of heat transfer in solids and heat transfer in fluids. In solids, conduction often dominates whereas in fluids, convection usually dominates.

Conjugate heat transfer is observed in many situationsfor example: conduction through solids, free and forced convection in the gases/fluids and thermal radiation.
The three main modes of heat transfer:
‐ Conduction is heat transfer that occurs when a temperature difference exists across a stationary medium.
‐ Convection is the heat transfer between a surface and a moving fluid when there is a temperature difference between the two.
‐ Radiation(thermal radiation) is the emission of energy in the form of electromagnetic waves. In the absence of an intervening medium ,there is net heat transfer by radiation between two surfaces at different temperatures.

Graphic card
A graphics card (also called a display card, video card, display adaptor or graphics adaptor) is an expansion card which generates a feed of output images to a display device like monitor. the graphics card is responsible for rendering an image to your monitor. it does this by converting data into a signal which your monitor can understand.

Geometry
Download and import model in geometry.

Share topology to make sure that we get conformal mesh.
Meshing
Baseline mesh

Refined mesh
Insert 4 body sizing and select 1 component in each of them and refine mesh by varying the element size.

select the body and edit the element size similarly for other bodies.

Named selection

Meshing

Setup
general setup
solver type: pressure based
velocity formulation: absolute
time: steady state

Turbulence model: K-Omega SST

Materials
copy solid materials from fluent data base.

silicon is used for manufacturing processor, since silicon is not available in fluent database. so, we copy a material and edit its properties as persilicon material.

material properties

Base - Aluminium

Fins - Copper

Processor - Sillicon

Enable source term for processor and set value 15625000W/m^3

Boundaries
inlet
type: velocity inlet

Outlet
Type: pressure outlet

Symmetry
type: symmetry

Report definition

create report definition for temperature.

similarly create report definition for surface heat transfer coefficient.

Initialize
Standard initialization from Inlet
Create contour for temperature.
Run simulation.

RESULTS
At velocity 1m/sec
Scaled residuals

Processor

Base with processor

Fins

GPU

Temperature distribution inside enclosure

From the results output table we can observe that by increasing the velocity of air, processor temperature is decreasing. this is because as the velocity of flow is increased, more amount of heat is carried away by air. the heat transfer coefficient is highest in the regions which are in contact of the processor. this region is  not affected by the change inflow velocity since there is no airflow present, hence the maximum heat transfer remains the same in the region exposed to the fluid flow. also we can say that refined mesh gives more accurate result compared to course mesh.

KINDLY DOWNLOAD THE SETUP FILES AS ITS NOT UPLOADING

https://drive.google.com/file/d/13Q4QpEkL9l3up6ibkPC38B_8l_0Jp2rE/view?usp=sharing

Conclusion
The refined mesh provides the more accurate result than coarser mesh. Accuracy can be increased by increasing the no. of elements. The temperature of the graphic card decreases with the increase in velocity because as the velocity of flow is increased, more heat is carried away by the air, hence graphic card cooled.

PLEASE CLICK AND DOWNLOAD THE SETUP FILES

https://drive.google.com/file/d/13Q4QpEkL9l3up6ibkPC38B_8l_0Jp2rE/view?usp=sharing