**9.1 Geometry creation**

As mentioned, natural gas adsorption on nanotubes depends on its varied features, including the diameter of nanotubes, construction method, gas arrangement in the nanotube structure, pressure, and temperature. The free spaces of nanotubes have the highest potential for natural gas adsorption. With an increase in the loading pressure, adsorption increases, but as the temperature of the adsorption medium enhances, adsorption decreases. A model was developed for natural gas storage in a vessel containing nanotubes. In fact, the adsorption phenomenon and gas storage of natural gas were modeled here. It was seemed that multi-wall nanotube could be a best choice for adsorbent, and so, multiwall carbon nanotube was used as adsorbent in this chapter. A container with a volume of about 100 ml and has inlet and outlet diameters of 6.35 mm, which we see in **Figure 5**. This container has an inner diameter of 35.85 mm and a height of 25.3 mm. It also has a porosity of 98.4%. Multiwalled nanotubes are uniformly placed inside the container, which can be considered as a porous medium [1].

The hypotheses that must be considered before solving the problem are:


In addition, the properties and composition are listed. According to the assumptions mentioned above, the governing equations are obtained [1]. To simulate natural gas storage in carbon adsorbents, the equations must be solved

**Figure 5.** *Schematic of the geometry used here [1].*
