In this chapter we apply the macroscopic balance equations that have been developed in Chap. 3 to study a few important problems. First, the pipe flow of a Newtonian fluid is considered in Sect. 5.1; then, in Sects. 5.2 and 5.3, this case is generalized to non-Newtonian fluids, stressing how the velocity profiles and the consequent pressure drops are functions of the fluid constitutive equations. In Sect. 5.4. we analyze the flow of a fluid across porous media, stressing when and how a fixed bed becomes fluidized. Then, in Sect. 5.5 we start considering non-stationary flows, introducing the Quasi Steady State (QSS) assumption that will be used extensively in the following. Finally, in Sect. 5.6, we study capillary flows, i.e. the fluid flows that are driven by surface tension effects.