Abstract:
The enhanced thermal characteristics of nanofluids have made it one of the most raplidly growing research areas in the
last decade. Numerous researches have shown the merits of nanofluids in heat transfer equipment. However, one of the
problems is the increase in viscosity due to the suspension of nanoparticles. This viscosity increase is not desirable in
the industry, especially when it involves flow, such as in heat exchanger or microchannel applications where lowering
pressure drop and pumping power are of significance. In this regard, a critical review of the theoretical, empirical, and
numerical models for effective viscosity of nanofluids is presented. Furthermore, different parameters affecting the viscosity
of nanofluids such as nanoparticle volume fraction, size, shape, temperature, pH, and shearing rate are reviewed. Other
properties such as nanofluid stability and magnetorheological characteristics of some nanofluids are also reviewed. The
important parameters influencing viscosity of nanofluids are temperature, nanoparticle volume fraction, size, shape, pH, and
shearing rate. Regarding the composite of nanofluids, which can consist of different fluid bases and different nanoparticles,
different accurate correlations for different nanofluids need to be developed. Finally, there is a lack of investigation into the
stability of different nanofluids when the viscosity is the target point.
