Mechanical Engineering
Hadi eskandari; Moslem Ghanbari
Abstract
The present study deals on the geometry effects of the spherical pressure vessel(SPV) and the crack configuration on the variation of the stress intensity factor (SIF) through the crack line. The pressurized vessel is subjected to the pressure and thermal gradient (thermo-mechanical loading). The 3D ...
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The present study deals on the geometry effects of the spherical pressure vessel(SPV) and the crack configuration on the variation of the stress intensity factor (SIF) through the crack line. The pressurized vessel is subjected to the pressure and thermal gradient (thermo-mechanical loading). The 3D analysis of defected thick-walled pressurized sphere vessel is done using the numerical Finite Element Method (FEM). This work covers a wide range of the crack configurations in vessels with different geometries. The effect of the various parameters such as thermal gradient, RO/Ri, a/c and a/t on the variation of the dominant first mode of SIF through the crack front is studied. The obtained SIF’s are compared with the mechanical loading results (in the absence of the thermal gradient). The results show that parameters such as the aspect ratio of the crack, the ratio of the crack depth, the pressure vessel wall thickness and also the temperature gradient have significant effects on the distribution of the SIF through the crack line. It can be seen that the thermo-mechanical condition is more critical.
Mechanical Engineering
Hadi eskandari
Abstract
This work pertains to investigate the values of the stress intensity factor (SIF) in a functionally graded spherical pressure vessel with an embedded surface defect (semi elliptical crack) under thermo-mechanical loading. The three dimensional finite element analysis is performed to evaluate the SIFs ...
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This work pertains to investigate the values of the stress intensity factor (SIF) in a functionally graded spherical pressure vessel with an embedded surface defect (semi elliptical crack) under thermo-mechanical loading. The three dimensional finite element analysis is performed to evaluate the SIFs through the crack front for a wide range of crack profiles and the various layer thickness. It is assumed that the elastic modulus of sphere varies exponentially in the radial direction of the vessel.The effect of non-uniform coefficient of thermal expansion (CTE) on the fracture parameters is also studied. The obtained results show that the material gradation of spherical pressure vessel can considerably affect the distribution of the SIFs along the crack front. The gradation of material, the wall thickness of spherical pressure vessel and the profile of crack front can affect the critical point through the crack front which is apt to the crack growth.
Mechanical Engineering
Seyed Masoud Vahedi; Farzad Parvaz; Mohsen Khandan Bakavoli; Mohammad Kamali
Abstract
Separation of suspended droplets in a fluid flow has been a great concern for scientists and technologists. In the current study, the effect of the surface roughness on flow field and the performance of a gas-oil cyclone is studied numerically. The droplets and the turbulent airflow inside the cyclone ...
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Separation of suspended droplets in a fluid flow has been a great concern for scientists and technologists. In the current study, the effect of the surface roughness on flow field and the performance of a gas-oil cyclone is studied numerically. The droplets and the turbulent airflow inside the cyclone are considered to be the discrete and continuous phases respectively. The Reynolds stress model (RSM) is employed to simulate the complex, yet strongly anisotropic, flow inside the cyclone while the Eulerian-Lagrangian approach is selected to track droplet motion. The results are compared to experimental studies; according to the results, the tangential and axial velocities, pressure drop, and Euler number decrease when the surface roughness increases. Moreover, the cyclone efficiency drops when the vortex length decreases as a result of a rise in surface roughness. The differences between the numerical and experimental results become significant at higher flow rates. By calculating the impact energy of droplets and imposing the film-wall condition on the walls, splash does not occur.
Mechanical Engineering
Mahmoud Afshar; Hamid Rad
Abstract
In this paper, an advanced analysis of a novel hybrid compression-absorption refrigeration system (HCARS) for natural gas dew point control unit in a gas refinery is presented. This unit separates the heavy hydrocarbon molecules in the natural gas, which is traditionally carried out by natural gas cooling ...
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In this paper, an advanced analysis of a novel hybrid compression-absorption refrigeration system (HCARS) for natural gas dew point control unit in a gas refinery is presented. This unit separates the heavy hydrocarbon molecules in the natural gas, which is traditionally carried out by natural gas cooling in a compression refrigeration cycle (CRS). The power input required for the refrigeration cycle compressors is usually provided by gas turbines. The low efficiency of gas turbines and the excessive power required for running the CRS compressors have made it crucial to investigate different means to decrease the energy consumption of this cooling system. The waste heat of gas turbines flue gas can be recovered and utilized as the heating source for running an absorption refrigeration system (ARS) to provide part of the needed cooling load; hence, a hybrid compression absorption refrigeration system (HCARS) is launched. In this work, the application of HCARS is extended to the Fajr-e-Jam gas refinery currently operating with a CRS, and an advanced exergetic analysis of the proposed ARS is performed to further improve the proposed system. The effect of different variables on the performance of the proposed HCARS is also inspected. The proposed system and these analyses are novel for the gas refinery dew point control unit. Real CRS operational data are utilized in all the investigations, and proper means are presented for the validation of the simulation results. The proposed system resulted in 63% additional cooling capacity of the HCARS (12550 KW) in comparison to the current CRS (7670 kW) for the equal natural gas consumption, which overall saves about 50000 SCMD of natural gas. Based on the exergy analysis of all the equipment, the exergy efficiency of the proposed ARS is 0.155. In addition, the parametric study of the effects of the gas turbine flue gas exit temperature and flow rate, ambient temperature, partial load operation of CRS, absorption solution flow rate, and concentration on the HCARS performance is carried out. These studies should provide the information needed for operating the proposed system in different situations.
