Single and two-phase discharge from a pressurized vessel

Abstract

The objective of this work was to establish models for the blowdown process of partially filled pressure liquefied vessels and to validate the models by comparison with experimental pressure measurements. On the basis of experiments using small 400 mL steel pressure vessels with creep and knife induced cracks, a crack opening model was developed using the Crack Opening Displacement theory and plastic displacement assumptions. For a single-phase discharge, an expression for the unsteady compressible choked flow through openings of varying areas was developed. The results of this blowdown model were compared with experimental pressure measurements obtained for nine small vessels filled with argon and water - at different fill levels (70, 80 and 90%) with different initial pressures. The influence of the speed of crack propagation and discharge coefficient were evaluated. The simulations of the single-phase model were found to be in reasonable agreement with the experiments. The work also presents a comparison of several available two-phase blowdown models applicable to the discharge of a pressure liquefied gas (simulated here by refrigerants R11, R22 and R123). Some modifications to these models were also examined. The two-phase models did not seem to adequately describe the experimental results even when the model parameters were adjusted to suit the experiments.