This Book is intended to generate mathematical formulation using nonlinear partial differential equations that reflect the physics of flow dynamics, in order to investigate how molecules, move in micropolar and nanofluids when subjected to various constraints. These fluids demonstrate the effects of local rotary inertia and thermal conductivity that make appropriate non-Newtonian fluid models. The models developed in this work, in fact, take into account the Brownian motion and thermophoretic effects that replicate how nanoparticles move through the molecules of a base fluid and occasionally collide with one another. It is required to introduce and modify the well-known Navier-Stokes equations when discussing the momentum and heat transport in nanofluid flow that explain the relationships between the momentum, pressure, energy, and density of a moving fluid. In this book, authors attempt to develop a computational model that includes a wide range of real-world heat transfer in nanofluids. Hopefully, reading this book will offer the reader a detailed overview of the study of heat transfer in nanofluid flow.