Many applications and industrial processes may necessitate the storage of large amounts of gases at high pressures. These compressed gases could be extremely dangerous if unintentionally released. since they could be poisonous or combustible when mixed with air. This research seeks to create a CFD model and undertake an analytical investigation of the process of de-pressurization of high-pressure gas from a vessel. The vessel to be studied is used in a pneumatic power system used to operate the control surface of a flying vehicle. The study involved two working fluids (nitrogen and helium). The discharging process is considered as a typical mass and heat transfer problem solved analytically by adopting The First Law of Thermodynamics to an unsteady flow control volume and simulated by employing transient flow analysis to the CFD model. The research was carried out on 440 bars (absolute pressure) of pressurized gas vessels. Working gases for the study included nitrogen and helium. Analytical solution results for the two different gases have been compared with the CFD simulation results to assess the CFD model's accuracy. A good match is achieved when the gas temperature, pressure, density, and outlet mass flow rate variations are compared. The results demonstrated
a good match between the CFD and analytical data, proving the validity of the CFD model.