The purpose of this chapter is to model the nanofluid flows. First, the classification of dispersed liquids and the conditions under which nanofluid flows can be described in the framework of continuum mechanics are discussed. It is shown that such flows can usually be described within the framework of single-fluid transport equations. Since heat transfer is an undoubted priority from the point of view of various thermophysical applications, the convective heat transfer of various nanofluids, including the fluids with the non-Newtonian rheology is analyses in detailed. Chapter 6 demonstrates that the efficacy of nanofluid utilization in heat exchangers is largely determined by the flow regime, i.e. laminar or turbulent. It is therefore imperative to examine the laminar–turbulent transition conditions. Examining this problem is the second objective of this chapter. The last problem that is considered in this chapter is the mixture of fluid and nanofluid in micromixer.