A Thermodynamics Study for a Mixture of Natural Gas & Water Flowing Through a Supersonic Nozzle

• Main Author: Chan, Yen Pinng
• Format: Final Year Project
• Language: English
• Published: Universiti Teknologi PETRONAS 2011
• Subjects: TJ Mechanical engineering and machinery
• Online Access: http://utpedia.utp.edu.my/10134/1/2011%20-%20A%20Thermodynamics%20Study%20for%20a%20Mixture%20of%20Natural%20Gas%20%26%20Water%20Flowing%20Through%20a%20Supersonic%20N.pdf; http://utpedia.utp.edu.my/10134/

In order to meet the specifications of transportation of natural gas in pipelines, there is a need for efficient separation of water from natural gas mixture. To date, supersonic separation has proven to be efficient in such a physical separation, yet there is limited study on the thermodynamic of the system. Lack of suitable equation of state in fluid flow simulation software ANSYS FLUENT 12.0 to model the non negligible density changes in the compressible flow also calls for a source code that can introduce real gas equations, that's also appropriate for hydrocarbon systems. With that, the objective of this Final Year Project will focus on understanding the thermodynamics of natural gas dehydration and producing a solution scheme based on Soave-Redlich-Kwong equation of state using user defined functions in computational fluid dynamics (CFD) software ANSYS FLUENT 12.0 to predict flow behaviour and changes in other thermodynamic properties. Therefore, scope of study for this project includes thermodynamics, real gas equation of state to accurately study the compressible, turbulent, high velocity, single phase water vapour flow behaviour and solution by means of computational fluid dynamics (CFD) software ANSYS® FLUENT 12.0 in two-dimension. This will be done through extensive literature review, identification of validation literature, writing of solution mechanism, performing CFD simulation and finally post-processing for analysis. Here, validation of simulation was done against Yang et al's (2009) paper on numerical simulation of non equilibrium spontaneous condensation in supersonic steam flow. Main findings showed that density change in compressible, high velocity flow does significantly influence the thermodynamic properties of the fluid flow system and super cooling resulting from isentropic expansion was also observed. This further verified that the source code written for using Soave-Redlich-Kwong equation of state to model density changes is successful. It was also proven that Soave-Redlich-Kwong equation of state is more accurate and reliable when it comes to modelling a system with high pressure variation, compared to ideal gas law. This dissertation thus presents the results from literature review, solution methodology, findings of this project and analysis. It is believed that such a study will aid in understanding the system in order to achieve efficient separation of impurities from natural gas in the future.