A method for calculating the void fraction of two-phase leakage ports of storage tanks

Abstract

Abstract The problem of leakage of superheated liquids such as LPG, LNG, LCG and AML is widely valued in the process industry. The key to superheated liquid storage and transportation is to prevent cracks due to unexpected situations such as tank overpressure, pipe corrosion and violent collisions. When the tank wall ruptures, the air pressure inside the tank drops sharply and a violent phase change occurs in the degraded liquid inside the tank to maintain energy balance. The liquid instantly evaporates into a gas, releasing a huge amount of energy to form a flash, and this leakage can lead to violent phase changes and two-phase flash jets containing large amounts of liquid droplets and steam, and further lead to major safety accidents such as fires, explosions and the spread of toxic substances. In this work, the pressure drop in the tank during a leak and the phase change at the leak caused by the pressure change at the orifice are investigated through theoretical analysis and experiments. Based on the ideal gas equation of state, mass conservation, gas-liquid non-slip and thermodynamic equilibrium, the pressure drop inside the tank and the phase change at the orifice during the whole leakage process are modelled and validated, and the results show that the model is in good agreement.