The effect of highly conductive thick walls on the mini channel heat transfer performance is systematically addressed while two constant heat flux sources are considered at the bottom of the channel. The influence of using different mass fractions of Al2O3 nanoparticles dispersed in water as working fluid are studied. The buoyancy effects on the thermal performance and pressure drop of the mini channel are also investigated. The finite volume method is employed to simulate the flow and heat transfer of nanofluid in the channel. The results show that the axial heat transfer is an important effect in mini channels with thermal conductive walls and should be taken into account. It is found that the presence of nanoparticles with the mass fraction of 5% and 10% drops the maximum temperature (and increases the pressure drop) by 1.28% (17.0%) and 1.48% (41.0%), respectively when Reynolds number is 500 and neglecting buoyancy effects. The presence of buoyancy effects reduces the pressure drop by 21.08% in a case with Reynolds number 500 and the nanoparticles mass fraction 5%. This is while the presence of buoyancy effects would decrease the maximum temperature by 1°C.
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