One of the most significant scientific challenges in the industrial
area is cooling, which applies to many diverse productions, including
microelectronics, transportation and manufacturing. Technological
developments such as microelectronic devices operating
at high speeds, higher-power engines, and brighter optical devices
are driving increased thermal loads, requiring advances in cooling.
The conventional method for increasing heat dissipation is to increase
the area available for exchanging heat to use a better heat
conductive fluid. However, this approach involves an undesirable
increase in the size of a thermal management system; therefore,
there is an urgent need for new and novel coolants with improved
performance. The innovative concept of ‘nanofluids’ – heat transfer
fluids consisting of suspended of nanoparticles – has been
proposed as a prospect for these challenges [1].
Maxwell was the first presenter of a theoretical basis to predict
a suspension’s effective conductivity about 140 years ago (1873)
and his theory was applied from millimeter to micrometer sized
particles suspensions but Choi and Eastman [2] introduced the
novel concept of nanofluids by applying the unique properties of
nanofluids at the annual Mechanical Engineering meeting of
American Society at 1995. Goldstein et al. [3] added the condition
that the particles must be in colloidal suspension. Choi and hisothers used well-known predictive correlations. Their works have
been both experimental and theoretical [12].
This review focuses on the stability of nanofluids, which is critical
to eventual utilization of nanofluid in practice. The subject was
put into consideration recently since different investigators reach
different results with the same nanoparticles. Therefore, it was
concluded that stability measurement and investigation for each
nanofluid preparation may be leading to a standard way of preparation
and unified data. Hence, experimental studies on preparation
and different stability methods of nanofluids are reviewed.
Theoretical attempts made to explain the associated characteristic
mechanisms are also outlined. In addition to these, the measurement
methods proposed for the determination of stability are summarized
and thermophysical property predictions of the models
are compared with experimental findings, and significant discrepancies
are specified.