Rapid calculation procedure to determine the pressurizing period for stored cryogenic fluids

The pressure of the stored fluid in cryogenic vessels increases if no boil-off gas is vented over long periods of time. From a thermodynamic point of view, an isochoric change of state takes place and the heat flux into the vessel rises the internal energy of the fluid. For the representation of the isochoric change of state, we constructed (Δu/v) versus x1 diagram with 1 x 105 Pa reference as a basis for LNG, LPG and R13a. The objective of the present work is to present thermodynamic design charts to facilitate a rapid calculation procedure to determine the pressurizing period of a transport vessel containing LNG or LPG or R134a cryogenic fluids. It is expected that the methodology presented in the paper could serve as a tool in determining the pressure rise due to boil-off phenomena. Specific examples are given for computing the pressurizing period using the charts provided.