Week 6 - CHT Analysis on a Graphics card

Aim:- CHT Analysis on a Graphics card

objective:-

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.

theory:-

CHT(conjugate heat transfer):- 

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 situations. For example, heat sinks are optimized to combine heat transfer by conduction in the heat sink with the convection in the surrounding fluid.

Heat Transfer in a Solid:
heat transfer in solids, if only due to conduction, is described by Fourier’s law defining the conductive heat flux, q, proportional to the temperature gradient Conduction is the transfer of energy from the more energetic particles of a substance to the adjacent less energetic ones as a result of interactions between the particles. it is due to the combination of vibrations of the molecules in a lattice and the energy transport by free electrons. Conduction can take place in solids, liquids, or gases. In gases and liquids, conduction is due to the collisions and diffusion of the molecules during their random motion.

Heat Transfer in a Fluid

Convection is the mode of energy transfer between a solid surface and the adjacent liquid or gas that is in motion, and it involves the combined effects of conduction and fluid motion. The faster the fluid motion, the greater the convection heat transfer. Convection heat transfer is complicated since it involves fluid motion as well as heat conduction. The fluid motion enhances heat transfer (the higher the velocity the higher the heat transfer rate).

case set up

in ansys fluent application

Geometry:

Open spaceclaim and drag down the graphic card file repair any error present and select share topology to activate the sharing information b/w deferent section and close the application

Mesh: -

name face of tunnel by inlet outlet and symmetry

and graphic card part as body and name fin, base and processer

meshing

afetr meshing close the mesh apllication 

case setup

fluent setup chech mesh quality evry this is rigth then move to seting up the solution

in matrials add 4 solid matrials aluminium, steel, copper and silicon 

in fluid air is by default is there

cell zone present in physics section 

for fins

for base

for processer : here heat source also added for 10w power

heat geneation = power /volume

`Q^.= 10/(8*8*10^-9)=1.5625*10^8`

heat genearation

for air flow

general

viscuous model

boundary condtion 

inlet

velocity inlet

v=1ms

outlet 

pressure outlet

p=0

afetr phisics set up move to solustion section define plots to look into results

once all the set up done intilize the solution 

and set up the countor for post processing and animation geneartion

contour

animation creation

after all this calculate the solution wait till simulation runs and look for results 

result

for 1ms inlet velocity

 

processer/core , base and fin temprature plot

post processing resluts of temrature ,pressure and velocity 

graphic card tempraure result ost processing

for 3 ms in let velocity

processer/core , base and fin temprature plot

 post processing results temprature and velocity

temprature distribution on graphic card

for 5 ms

processer/core , base and fin temprature plot

post processing resluts of temrature ,pressure and velocity 

temprature distribution on graphic card

conclusion

inlet velocity	max core temp in k	max core heat transfer coefficient in w/(m^2 k)	max base temp in k	max fin temp in k
1m/s	485	459	413	482
3m/s	400	862	348	379
5m/s	378	1110	333	376

from max temp in continueouly droping as the inlet velocity increasing and heat transfer coeffient is incresing 

this is beacause the heat transfer coefficent is function of prandlt number and reynolds numver 

wkt reynolds number is directly propostion to velocity thats y the HTC incresing due to this heat transfer rate is increased as a result there is drop in temp of graphic card matrials 

from results it can be seen that increasing in letvelocity drop the tempof component so to accumdate this facility now days high properming graphic cards come with fan to inuce force convection and remove heat from the graphic card  component