Conjugate Heat Transfer Analysis on a graphics card

Objective:

Performing a CHT simulation on a graphic card board .To calculate heat transfer coefficient at different ponts ,to determine processor temperature ,also to identify potential heat spots, if any and to show that the simulation has achieved convergence with appropriate images and plots

Model & meshing:

An enclosure around the board was created to depict the the physics of flowing air

Baseline mesh:

Cut section of mesh.

method -automatic with default element size

Conditions:

Procesor was appointed as heat source 5e7w/m3

inlet velocity of air : 5m/s

temperature of inlet air :300k

The residuals almost converged at around 100 iterations .

Temperature contoure

Max temperature attaned by processor was 333k

As conductivity of aluminium is more fins are usually made of such material to maximize heat desipation to surrounding .

Boards are made of material with lower conductivity as many components are mounted on it and they must be insulated .

Velocity contour :

The contour that we\'ve obtained are not that clear as the element count is less

element count was around 1lac

A line at the board plain was drawn to get the variation of temperature across the board from start to end procesor being at middle .

max temp of board was around 305k.

Refined mesh:

As the geometry was geometric in shape hexagonal meshing was prefered so type was set to hex-dominent .

element count around 4.7 lac

Enclosure mesh was refined but the type was kept the same (tetrahedrons )

Residuals :

we can see that the residuals converged at around 120 iterations

Temperature contour :

Max temperature attained by processor was around 322k

Temperature distribution on the board from left to right .

Wall heat transfer coefficient :

velocity contour:

Due to the no slip boundary conditipn velocity becomes zero at the board and at the walls but increases drastically the area above it as the area decreases .

• Pressure is directly proportional to temperature also when a restriction in introduced it is velocity of air at that point decreases and the hot air slows down at that point which i bad for convective heat transfer.
• Also as behind a restriction pressure is low and as velocity of air above the restriction is high it intoduces a recirculating zone where the velocity of air is really low which is bad in our case.

Experiment:

Case 3:

In this meshing was kept the same just the heat source value was changed to 5e4 just to check the sensitivity of the simulation

Results:

A increase in temperature of just 2 degree C was detected with the temperature contour