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-   -   Flow around heatsink with heat transfer (https://www.cfd-online.com/Forums/fluent/200822-flow-around-heatsink-heat-transfer.html)

S Mughal April 13, 2018 14:06

Flow around heatsink with heat transfer
 
Hello, this is my first post so please be kind.

i am setting up and running simulations for my dissertation of a heatsink operating in forced convection with heat transfer between the heatsink and fluid. the geometry and parameters are the same as an experiment conducted by Abd el Baky here https://1drv.ms/b/s!AgPMO1mLifl4wdVpH4neHet5cxjlUA and my aim is to get similar results and compare turbulence models.

so i have set up and run the simulation with an inlet velocity of 2.167 m/s, and a heat flux applied to the bottom of the heatsink of 10000W/m^2, corresponding to a volume flow rate of 0.0035m^3/s and a heater power of 80W from the experiment. the (steady state) simulation runs fine and converges with second order schemes no problem. the results look good and nothing odd seems to be happening.

what i dont understand is: how do i get the heat transfer rate from the heatsink to the fluid in post processing? what i understand is that i should go to the reports section, then fluxes, then select 'total heat transfer rate' and then select some items from the list. what i am unsure of is which items to select. i assumed it was all of the interfaces (excluding the shadows) but this totalled up just gives me 80 W no matter what my flow rate is. the heat transfer rate should change with flow rate as it does in the experimental data but even if i increase the flow rate (while keeping the heat flux under the heatsink unchanged), the total heat transfer rate stays the same. if i change the heat flux under the heatsink to say 25000 W/m^2 (corresponding to a heater power of 200W) then the same procedure above will give me a total heat transfer rate of 200W.

What am i doing wrong? which items am i supposed to select to give me the correct overall heat transfer rate from the heatsink to the fluid?

thanks in advance


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