MATHEMATICAL MODELING OF BLOWDOWN OF GAS FILLED PRESSURIZED SYSTEMS

Abstract

This study includes the development of a mathematical model for simulation of blowdown of a vessel containing gas (single component and multicomponent) based on two equations of state .These comprise of ideal gas equation and Soaves Redlich-Kwong (SRK) equation of state. The results obtained from the above equations are compared with experimental data for single and multi-component single phase(gas) systems. The temperature and pressure profile of the fluid inside the vessel and temperature of inner vessel wall are studies for three gases i.e. hydrogen, helium and methane and there mixtures. Another major part of the study includes parameter analysis i.e. different pressures and temperatures in the ranges 15-50MPa and 285 -310K respectively. Other parameters which are varied and studied are the volume of the vessel to be blowdown and the orifice diameter from where the gas exits the vessel. It can be concluded from this study that the temperature profile of the bulk gas decreases rapidly first and then rises gradually where as the temperature profile of vessel wall temperature and the pressure profile of the vessel reduces gradually. Parameter study for composition yields not very significant changes in the temperature of wall and pressure of vessel with the change in concentrations of the constituents. In comparing the concentration variation study, it can be seen that maximum sensitivity of the temperature and pressure profile is there for the case when methane is kept constant and hydrogen and helium concentrations are varied. Parameter study of the orifice diameter depicted significant dependency of the depressurization time on the orifice diameter.