| dc.description.abstract | This thesis investigates the phase transition during rapid depressurization of liquefied gases, a crucial research field for industries like LPG storage and transportation, gas separation processes, and oil and gas production. The Stiffened-Gas equation of state describes carbon dioxide behavior during depressurization, which can lead to BLEVE (Boiling Liquid Expanding Vapor Explosions). As per the objective of this thesis, a comprehensive literature study on phase change and BLEVE has been done. To achieve the rest of goals, this study offers an in-depth exploration of carbon dioxide (CO2) thermodynamic behavior during rapid depressurization, leveraging the Stiffened Gas Equation of State (SG-EOS) as a fundamental tool. The central objective is to attain a comprehensive understanding of CO2's intricate thermodynamic responses in such scenarios, particularly focusing on the isentropic expansion process. This thesis discusses the selection of an EOS (Equation of State) for a BLEVE model, which is essential for describing the relationship between state variables in thermodynamic equilibrium states. The Stiffened Gas Equation of State (SG-EOS) is used to describe the metastable phase of liquids and gases under high pressure and temperature conditions. The thesis considers the properties of the SG-EOS, such as pressure, entropy, speed of sound, ratio of specific heats, Helmholtz free energy, specific enthalpy, and specific internal energy. The state calculation is done by allowing the Pressurized Liquefied CO2 (PLG) to expand isentropically from its saturation state (293K). The thermodynamics state variables are recorded using Matlab code Thermodynamics masters from the Github Thermodynamics tool for H2O, H2, and CO2. The state change data is used to evaluate SG-EOS and find suitable values for γ and p∞. The density estimation is done separately for a specific set of temperatures and pressure. The investigation encompasses vital parameters, including pressure, temperature, density, and specific internal energy. The core findings and discussions revolve around the intriguing relationship between the ratio of specific heat (γ) and the infinity pressure (P∞). The study reveals a distinctive non-linear connection between these two factors, characterized by a convex curve. The P∞ vs γ curve has fitted best for isentropic expansion process from saturation state (293K) to 4.0Mpa. This relationship significantly influences CO2's behavior during depressurization, especially with regards to phase transitions and explosive tendencies.
Keywords: Depressurization, isentropic expansion process, Stiffened-Gas equation of state, P∞ vs γ curve, BLEVE | |
