Lennard-Jones fluid confined in slit nanopore was studied in this research. The results that based on Molecular Dynamics simulation, shows that fluid molecules in these nanopores distribute unevenly. These molecules strongly tend to gather adjacent to the walls even when no attraction force between fluid molecules and walls. Unevenly distributed molecules led to increase the system entropy and make more stable system. The effects of temperature, density, surface separation, fluid-wall interaction and confined fluid density have been considered in this research. Confined fluid density in open slit nanopore, was estimated with its equilibrium with bulk fluid. This is usually different of bulk fluid density. This density decreases with increasing temperature and increases with increasing bulk fluid density. Also fluid-wall interactions play an important role in confined fluid density. For example, when attraction force between fluid-wall molecules increased, fluid molecules near the walls show solid-like behavior and move in one slit along with walls only. Finally the adsorbtion excess that expresses the tendency of molecules to entrance and exit from nanopores has been considered. The results show that when surface separation were integer multiple of molecules diameter, the molecules strongly tend to enter in nanopore. Therefore density of confined fluid as compared with bulk fluid will be increased and if H/? is a half-integer number, this tendency will have at least amounted
