Stability evaluation and enhancement methods in nanofluids: A review

Demand of today's era for effective and efficient thermal systems has been increasing day by day. Several modifications are obligatory to fulfil the necessities of high heat transfer. Nanofluids are used instead of conventional fluids for the betterment of heat exchange devices. Stability of nanofluids plays vital role for their proper working in thermal systems. In this article, various stability evaluation and enhancement techniques are described in major part. To gain important indicative information about stability of nanofluids, various stability evaluation methods like sedimentation, zeta-potential, spectral absorbance and electron microscopy are deliberated. For improving stability of nanofluids, various stability enhancement techniques such as ultra-sonication, surfactant addition, surface modifications of nanoparticles and pH change are also described in this paper. To minimize pressure losses, to find optimum concentration of nanoparticles, long term stability and to explore hybrid nanofluids are some of the future research should be discovered. These are some of the technical challenges associated with nanofluids need to be solved for their better industrial applications.