Week 6 - CHT Analysis on a Graphics card

Aim

Perform a steady-state conjugate heat transfer analysis on a model of a graphics card

Introduction

A CHT (Conjugate Heat Transfer) analysis is useful where there are multiple modes of heat transfer in our computational domain, like conduction and convection. Having such a great number of applications for this type of simulation makes it important to be studied in depth.

Solving & Modelling approach

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.

Pre-processing and solver setting

geometry

enclosure is created over the geometry in spaceclaim

Mesh ( BASE MESH)

1) Target length 10mm for the enclosure

2) Traget lenght for the graphics card 2mm

NAME SELECTION

1)INLET = velocity inlet perform @ different velocity = ( 1 m/s , 3m/s , 5m/s)

2) OUTLET = pressure outlet

3)DOMAIN = wall

4) FIN

5) PROCESSOR

6) PCB

SETUP&SOLUTION

solver

Type : pressure based

Veloctiy formulation : Absolute

Time : steady state

viscous model : K-omega SST

Materials & their properties:

1) Fins --> Aluminium

Standard aluminium is available in Fluent database.

Density = 2719 Kg/m^3

Heat capacity = 871 J/KgK

Thermal conductivity = 202.4 W/mK

2) Processer --> Silicon

Since the silicon is not available in Fluent's solid database, I had to define it

Density = 2330 Kg/m^3

Heat capacity = 703 J/KgK

Thermal conductivity = 153 W/mK

3) PCB --> pcb (glass-reinforced epoxy laminate material)

Since the FR4 is not available in Fluent's solid database, I had to define it

Density = 55 Kg/m^3

Heat capacity = 1210 J/KgK

Thermal conductivity = 0.27 W/mK

4) Fluid --> Air

Standard air is available in Fluent database.

Density = 1.225 Kg/m^3

Heat capacity = 1006.43 J/KgK

Thermal conductivity = 0.0242 W/mK

Viscosity = 1.7894e-05 Kg/m-s

Cell zone condition

1 Fin - solid - Aluminium

2 processor - solid - silicon

3 Base - solid -PCB

4 Enclosure - fluid - air

BOUNDARY CONDITION

1) INLET - velocity inlet = perform @ different velocity = ( 1 m/s , 3m/s , 5m/s)

2) OUTLET = pressure outlet

Residuals

temperature of the processor

surface heat transfer coeffiecient

contour plots

velocity

temperature

surface heat transfer

velocity vector

HOTSPOT IN FIN

HOTSPOT IN PROCESSOR

result for base

5

325

-12.568 w/ m^2 K

case -2

Target length of the enclosure = 5 mm

Taget length of the gaphics card = 0.4 mm

1) velocity = 1 m/s

residual polt

temperature of the processor

surface heat transfer coeffiecient

velocity contour

temperature contour

velocity vector

1) velocity = 3 m/s

residual polt

temperature of the processor

surface heat transfer coeffiecient

velocity contour

temperature contour

velocity vector

1) velocity = 5 m/s

residual polt

temperature of the processor

surface heat transfer coeffiecient

velocity contour

temperature contour

velocity vector

Results

velocity	temperature of processor	surface heat tansfer coefficient
1	375	-4.568 w/ m^2 K
3	336	-7.800 w/ m^2 K
5	325	-12.806 w/ m^2 K

CONCLUSION

1. As the number of elements increases the accurate results of temperature distribution is obtained
2. From the above table, it is fairly notable that, the net temperature of components of graphics cards decreases with an increase in inlet velocity.
3. Hence it can be inferred that a higher inlet velocity results in better cooling and lower the average temperature thus keeping the components safe from damage.
4. 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.