Week 6 - CHT Analysis on a Graphics card

Aim: To perform conjugate heat transfer analysis on a graphics card assembly

Theory: Conjugate heat transfer is phenomenon of heat transfer between solid and liquid. This analysis shows the exact picture of heat transfer between the interface i.e. contact surface of solid and liquid. During the heat transfer both conduction and convection process happens. It simply means that travelled from solid body to fluid body, the conduction phenomenon takes place while heat transfer through fluid body, convection phenomenon happens.

This analysis is used I various application such as HVAC, electronic components, heat exchangers, etc.

Here graphics card is main source of generating heat. Fins which are attached with graphics card are used to dissipate the heat from graphics card through fins.

Geometry: the complete geometry is imported in space claim. This geometry having following parts

1. Boundary or enclosure
2. Fins
3. Graphics card
4. PCB

Mesh: for getting perfect mesh between different bodies, here we use share topology tool itself in space claim so that conforming type of mesh we get.

Here, first mesh course mesh generation and after taking results, I modified the mesh in fine size.

Number of nodes:15811

Number of elements:84283

Mesh type; Tetrahedron

Setup: here solver used is pressure based

Time : steady

Model

Energy equation is on

Viscous K-omega

Boundary condition

Material allotment

Part	Material	Thermal conductivity (W/mK)	Specific heat (J/Kg. K)	Density (Kg/m^3)
Fins	Aluminium	202.4	871	2719
Graphics card	Silicon	153	703	2330
PCB	Polystyrene	0.027	1210	55
Heat transfer fluid	Air	0.0242	1006.43	1.225

Here we assume heat dissipation of graphics card = 1 W

Volume of graphics card = 64 x 10 ^-9 mm^3

=

= 15625000

Results

For velocity 3 m/s

The maximum temperature obtained by graphics card is 316.97K.

The heat transfer coefficient is obtained -6.959.w/m2k

For 5 m/s

The maximum temperature obtained by graphics card is 313.47K.

The heat transfer coefficient is obtained -10.03.w/m2k

Conclusion

Conjugate heat transfer analysis is done with 3 different velocity value with 2 variations in mesh sizes.

The maximum temperature obtained by graphics card is 330.196K.

The converged solution is obtained at nearly 150 iteration because all the graphics values are almost constant.

The heat transfer coefficient is obtained -3.358.w/m2k

Comparison table

Sr. No.	Velocity	1 m/s	3m/s	5m/s
1	Htc	-3.358	-6.959	-10.035
2	Tmax	330.196	316.975	313.476
3	Tavg	330.196	316.975	313.476