Nanofluids, which are expected to
increase the heat transfer coefficient (HTC) with little pressure
drop penalty, have received considerable scientific interest during
the last decade [6–12]. Nguyen et al. [6] experimentally investigated
the heat transfer characteristics of Al2O3/water nanofluid in
a liquid cooling system and found that the HTC increased by 40%
at a volume concentration of 6.8%. Putra et al. [7] experimentally
studied the convective heat transfer of CuO and Al2O3 nanofluids
flowing in a horizontal tube and observed heat transfer deterioration.
They suggested the deterioration was caused by nanoparticle
deposition and particle/fluid slip. Wu et al. [8] investigated the
heat transfer characteristics of Al2O3/water nanofluids flowing in
a double-pipe helical heat exchanger. They found that heat transfer
was enhanced compared to the base fluid at constant Reynolds
number. However, little heat transfer enhancement was observed
based on the constant flow velocity. The above discussion showed
that comparable results from different groups vary widely.
Therefore, further research on convective heat transfer of nanofluids
is necessary.