Theoretical analysis and correlations for predicting properties of hybrid nanofluids

Numerous studies on nanofluids consisting of single nanoparticles are dispersed in the base fluid to make heat transfer fluids. Further progress in nanofluids resulted in the production of hybrid nanomaterials (nanoparticles), resulting in superior thermophysical properties and heat transfer enhancement. The main objective of this chapter is to provide a comprehensive review of the thermophysical properties of hybrid nanofluids up to date and the correlation used for predicting these properties. The main contributing factors that affect the thermophysical properties, such as stability, nanoparticle type, size, volume concentration, type of base fluid, temperature, surfactant, pH value, and sonication time, are also addressed. Various empirical correlations developed by researchers for the thermophysical properties of the hybrid nanofluids are compiled and reported. Finally, challenges with the stability and thermophysical properties of their correlations are summarized.