Flow through packed beds of granular materials, and for instance, granular activated carbon (GAC), is of great importance and has various applications in desalination, refinery, filtration, separation, and so forth. Hence, transport analysis and flow characterization of such problems have to be supported by experimental data. In the present study, flow transport through a packed bed of GAC, as an adsorbent material, is analyzed experimentally. The focus of the work is on the axial–vertical flow of air and argon through five different GAC grain samples to characterize the flow behavior in terms of GAC grain size. In addition, some other affecting parameters, including the fluid inlet pressure and the flow rate, are studied and their effects on the permeability of the porous bed as well as fluid pressure drop are presented. To study the effects of the gravity on friction factor and pressure drop, all tests are performed in two situations—fluid flow with the same and the opposite direction as the gravitational acceleration. It is found that gravity can increase the pressure drop about 10 to 400 Pa (about 10 to 25% higher) which is significant. Also, the pressure drops through the packed bed of GAC are found and the results are reported in terms of non-dimensional parameters of friction factor versus Reynolds number, to propose proper correlations for various fluids flowing in different directions through the applied GAC grains. Correlations, which are reported in this article, can be used in designing systems in which pressure drop is of great importance, and activated carbon in the vertical situation is utilized.