Abstract—Natural gas flow contains undesirable solid particles, liquid condensation, and/or oil droplets and requires reliable removing equipment to perform filtration. Recent natural gas processing applications are demanded compactness and reliability of process equipment. Since conventional means are sophisticated in design, poor in efficiency, and continue lacking robust, a supersonic nozzle has been introduced as an alternative means to meet such demands. A 3-D Convergent-Divergent Nozzle is simulated using commercial Code for pressure ratio (NPR) varies from 1.2 to 2. Six different shapes of nozzle are numerically examined to illustrate the position of shock-wave as such spot could be considered as a benchmark of particle separation. Rectangle, triangle, circular, elliptical, pentagon, and hexagon nozzles are simulated using Fluent Code with all have same cross-sectional area. The simple one-dimensional inviscid theory does not describe the actual features of fluid flow precisely as it ignores the impact of nozzle configuration on the flow properties. CFD Simulation results, however, show that nozzle geometry influences the flow structures including location of shock wave. The CFD analysis predicts shock appearance when p 01 /p a >1.2 for almost all geometry and locates at the lower area ratio (A e /A t ). Simulation results showed that shock wave in Elliptical nozzle has the farthest distance from the throat among the others at relatively small NPR. As NPR increases, hexagon would be the farthest. The numerical result is compared with available experimental data and has shown good agreement in terms of shock location and flow structure. Keywords—CFD, Particle Separation, Shock wave, Supersonic Nozzle. I. INTRODUCTION N gas processing industry, gas-expansion equipment is employed for obtaining low temperatures. As a result, natural gas flow could contain solid particles, liquid condensation, and/or oil droplets. Existing such undesirable phases in any natural gas pipeline might cause several problems in equipment and instrumentations. For instant, solid particles could deposit on the pipe wall leading to partially blockage the flow. The consequences could be worse as the accumulation grows up resulting in losing in flow pressure and reduction in transmission efficiency. Particle layers propagation tend to gradually form a plug that separates the pipe into two pressure sections: a high pressure section between the high pressure gas source and the plug and a second section at low pressure between the plug and the gas recovery division. In the upstream section, a pipe Esam Jassim is with the Prince Mohammed Bin Fahd University (phone: +9663-849-9314; fax: +9663-896-4566; e-mail: ejassim@ pmu.edu.sa). blast can occur due to pressure rise. The plug can also behave as a projectile that destroys the pipe when the pressure difference between the upstream and downstream sections increases. The deposition of particles inside gas pipelines is extremely undesired due to its environmentally and economically dangerous impact. The problems come up when the solid material clogs the fluid stream, even increasing pressure drop and causing pipe leaks or explosion. Also, a pipeline blow-out endangers human life as such accidents have resulted in human deaths in the past. In one incident, an explosion caused a large piece of pipe to strike the foreman, killing him [1]. Lysne [2] listed three incidents in which projectiles erupted from pipelines at elbows had caused loss of three lives and over $7 million (US) in capital costs. Another example is the Piper Alpha disaster in the North Sea of July 6th, 1988 which clearly demonstrated the catastrophic consequence of this type of failure where 165 of the 226 on board died. Further, the energy released during this tragedy was estimated to be equal to 20% of the UK energy consumption for that period [1]. The blockage incident due to deposition in natural gas pipeline that occurred on the Gas Export Pipeline (GEP) of the Matterhorn platform in 2007 had required three days for resuming [3]. During the remediation process, about 2400 bbl of condensate and 5 MMscf of gas were blown out. Statistical data showed that annually an operating expense greater than $500 million is allocated for particle deposition prevention [4], almost half of which spent for inhibitors [5]. Insulation of subsea Natural gas pipelines costs up to $1,000,000 per mile to alleviate second phase formation [5]. Although filtration process captures large particles (mainly >15µm), smaller size particles will escape the process and need to be effectively removed. Besides, the collision of the particles with the fibers of filtration media reduces the kinetic energy of the particles imported by the gas stream, eventuating adhering on the pipe wall. Such problems, among many others, turned researcher’s attentions to invent other methods of gas purification. However, coming up with a robust design that have capability to perform the task with minor problems is a challenge. Since the common design challenges in all natural gas-expansion applications are the compactness and reliability of process equipment, supersonic nozzles has been introduced as an alternative device to meet such demands. Recent research has introduced state of art technologies based on adiabatic cooling, the process of gas expansion in a supersonic nozzle employed for obtaining low temperatures. During the process, part of gas enthalpy transforms to kinetic Numerical Investigation of Nozzle Shape Effect on Shock Wave in Natural Gas Processing Esam I. Jassim and Mohamed M. Awad I World Academy of Science, Engineering and Technology International Journal of Chemical and Molecular Engineering Vol:7, No:6, 2013 344 International Scholarly and Scientific Research & Innovation 7(6) 2013 scholar.waset.org/1307-6892/3767 International Science Index, Chemical and Molecular Engineering Vol:7, No:6, 2013 waset.org/Publication/3767