Fluid flow and thermal analysis of Al2O3-water nanofluid in multi- microchannel heat sinks

Resumo

This work analyzes different working fluids (DI-water and Al2O3-water based nanofluid) flowing in a
copper microchannel heat sink consisting of 20 parallel rectangular channels of 29.23 mm in length, 1.2 mm in
width, and 1.2 mm in height for each microchannel and investigates their influence on the velocity flow field,
pressure drop, and heat transfer. The CFD software ANSYS FLUENT 2020 R2®

was applied. In the case of
Alumina-water nanofluid with an average nanoparticle size of 10 nm, different volume concentrations were used
(0.5% and 1 vol.%). A uniform velocity and temperature (293.15 K) were applied at the inlet of the heat sink.
The inlet velocity varied from 3.41 to 8.54 m/s, and the Reynolds number based on the hydraulic diameter and
inlet velocity varied from 400 to 1000. A heat flux corresponding to 165 W dissipated power for
an Intel®
CoreTM Serie X processor was applied at the bottom surface of the heat sink. It was possible to obtain
different temperature distributions, the pressure drop, and the requested pumping power consumption by
modifying the working fluid. Comparisons were performed on how the velocity and temperature fields changed
according to boundary conditions. The Alumina-water nanofluid provides a more uniform wall-temperature
distribution; the nanofluid with the highest concentration has the highest friction factor and the highest Nusselt
number regardless of the Reynolds number. The nanofluid thermal behavior with the volumetric concentration
increasing is probably due to the fluid thermal conductivity increasing. Even the higher pressure drop observed
for the Al2O3-water nanofluid, its effect on the pumping power consumption is acceptable (for the highest
nanofluid concentration and Reynolds number, the pressure drop is 93.40 kPa corresponding to a pumping
power of 3 W). Therefore, the microchannel heat sink and nanofluids seem a plausible solution for the cooling
challenge in microscale electronics due to the higher cooling performance.