Nanofluids Long-term Stability Challenges and Guidelines

Abstract

A nanofluid is a colloidal suspension of nanoparticles in any base fluid that displays a plethora of improved properties based on its field of applications, i.e., heat transfer, lubrication, and biomedical applications, over those of nanoparticles alone. Despite their improved properties, the real-world applications of nanofluids remain limited due to their gradual destabilization with time. Therefore, the stability of nanofluids remains a significant bottleneck that preventing their widespread application in numerous fields. Since a nanofluid is a colloidal suspension, Derjaguin-Landau-Verwey-Overbeek (DLVO) and non-DLVO theory have been utilized to elucidate the process of nanofluid destabilization. This chapter explores the underlying physics behind nanofluid destabilization and identifies significant factors that dictate the destabilization process. The roles of nanoparticle and base fluid properties, preparation method, external forces, operating conditions, and stabilizer presence on nanofluid stability have been examined in great detail. Different nanofluid stabilization strategies and stability evaluation methods are also discussed in the present chapter. This chapter discusses the desired properties for attaining long-term stability and identifies different challenges associated with the stability of nanofluids. Upon consideration of the abovementioned factors, the chapter provides summarized guidelines to ensure long-term nanofluid stability. This chapter concludes with a discussion on future research direction in nanofluid stabilization.