The exact modeling of the fast-fill process of Compressed Natural Gas (CNG) fueled storage bank occurring to Compressed Natural Gas Vehicle (NGV) cylinders is an unintelligible process, and should be thoroughly studied. In this paper, a theoretical model based on mass balance and thermodynamic laws has been developed to study dynamic fast filling process of CNG storage bank to vehicle's (NGV) cylinder. Because Methane occupies a large percentage (between 70% to 99%) of natural gas, for the sake of simplicity it is assumed that Methane is the only substance in Natural gas and thermodynamic properties table has been employed for case of real gas model based on methane. For modeling the heat transfer, the system has been treated as an adiabatic lump one. The result shows the initial pressure of storage bank has a big effect on the storage bank volume for bringing up the NGV cylinder to its target pressure (20 MPa). The storage bank volumes required for bringing up the NGV cylinder to its final (target) pressure (20 MPa) for various initial storage bank pressure, like 20.8 MPa (RPS = 1.04), 23 MPa (RPS = 1.15) and 25 MPa (RPS = 1.25) are respectively 22, 6 and 4 times the NGV cylinder volume. It is noted that RPS is the ratio of storage bank pressure (PS) to target pressure (PT) (In this research is 20 MPa). The results also showed that ambient temperature has a big effect on refueling process, chiefly on final NGV cylinder and storage bank conditions.
compressed natural gas; NGV cylinder; storage bank; fast filling process; thermodynamic analysis; entropy generation
