Amirkabir University of Technology Amirkabir Journal of Mechanical Engineering 2008-6032 53 11 2022 01 21 Effect of Magnetic Field on Motion, Deformation, and Separation Time of Newtonian and Non-Newtonian Droplets in a Flow‐Focusing Microchannel Effect of Magnetic Field on Motion, Deformation, and Separation Time of Newtonian and Non-Newtonian Droplets in a Flow‐Focusing Microchannel 5311 5330 4322 10.22060/mej.2021.19257.6989 FA Sima Mashafi Department of Mechanical Engineering, Faculty of Engineering, Kharazmi University , Tehran, Iran Mostafa Esmaeili Department of Mechanical Engineering, Faculty of Engineering, Kharazmi University , Tehran, Iran Journal Article 2020 11 14 In the present study, the effect of external magnetic field on the process of droplet formation with different sizes and frequencies in a flow-focusing micro-channel is numerically studied. Moreover, the influence of non-Newtonian properties on the droplet formation characteristics is investigated using two non-Newtonian Carreau and power-law models. To solve the continuity and momentum equations for unsteady, two-phase, and incompressible flow, the finite volume method is employed. A numerical algorithm based on the volume-of-fluid technique is used to determine the effect of Bond number (0 to 0.2) and Power-law indices (0.3, 0.6, and 1.3) on the droplet formation process along with their size and separation time. To validate the numerical solution, the formation of Newtonian fluid droplets at different values of magnetic field strength is compared with the results of other studies and very good agreement was observed. The results of the numerical solution show that the Carreau fluid droplet in the Bond number of 0.2 has the highest volume, which is equivalent to the dimensionless volume of 1.56. Also, the process of droplet formation is more affected by the magnetic field than by the non-Newtonian model. Besides, with developing the field strength, droplet separation time increases and as a result, larger droplets with lower frequency will be formed. In the present study, the effect of external magnetic field on the process of droplet formation with different sizes and frequencies in a flow-focusing micro-channel is numerically studied. Moreover, the influence of non-Newtonian properties on the droplet formation characteristics is investigated using two non-Newtonian Carreau and power-law models. To solve the continuity and momentum equations for unsteady, two-phase, and incompressible flow, the finite volume method is employed. A numerical algorithm based on the volume-of-fluid technique is used to determine the effect of Bond number (0 to 0.2) and Power-law indices (0.3, 0.6, and 1.3) on the droplet formation process along with their size and separation time. To validate the numerical solution, the formation of Newtonian fluid droplets at different values of magnetic field strength is compared with the results of other studies and very good agreement was observed. The results of the numerical solution show that the Carreau fluid droplet in the Bond number of 0.2 has the highest volume, which is equivalent to the dimensionless volume of 1.56. Also, the process of droplet formation is more affected by the magnetic field than by the non-Newtonian model. Besides, with developing the field strength, droplet separation time increases and as a result, larger droplets with lower frequency will be formed.

https://mej.aut.ac.ir/article_4322_31a262d6247f3513b19d1149102e116d.pdf

Amirkabir University of Technology Amirkabir Journal of Mechanical Engineering 2008-6032 53 11 2022 01 21 Optimization of The Slotted Gurney-Flap Geometry Applied to NACA 0012 Airfoil for Aerodynamic Performance Improvement Optimization of The Slotted Gurney-Flap Geometry Applied to NACA 0012 Airfoil for Aerodynamic Performance Improvement 5331 5348 4400 10.22060/mej.2021.19308.6999 FA Mostafa Kazemi PhD Student, Aerospace Engineering Department, Amirkabir University of Technology Ali Madadi استادیار Mahmoud Mani Aerospace Engineering Department, Amirkabir University of Technology Journal Article 2020 11 26 The salient aim of this paper is the shape optimization of an airfoil equipped with Gurney-Flap for aerodynamic performance improvement. The optimization of the slotted Gurney-Flap for improving the aerodynamic efficiency and increasing the lift force of NACA 0012 is the novelty of this research. The Genetic Algorithm, Artificial Neural Network, and Computational Fluid Dynamics are employed for shape optimization. The optimization variables include the height and thickness of the Gurney-Flap; also, the thickness and position of the slot. All analyses have been conducted at Re=0.45×106 and AoA=8o to simulate the take-off phase. After validation, the optimization process was conducted with two different fitness functions of Cl and L/D. According to the results, the geometry representing an optimized lift coefficient compared to the geometry with optimized L/D has a considerably higher height. Furthermore, the thickness of the slot in the first geometry is lower than the second geometry. As a result, the first optimized geometry leads to a 21.64 percent lift coefficient increment; there is a 293 percent increment in aerodynamic efficiency due to the second optimized geometry. As a result, it can be indicated that the help of slotted optimized Gurney-Flap can provide the required lift force for a short take-off landing distance. The salient aim of this paper is the shape optimization of an airfoil equipped with Gurney-Flap for aerodynamic performance improvement. The optimization of the slotted Gurney-Flap for improving the aerodynamic efficiency and increasing the lift force of NACA 0012 is the novelty of this research. The Genetic Algorithm, Artificial Neural Network, and Computational Fluid Dynamics are employed for shape optimization. The optimization variables include the height and thickness of the Gurney-Flap; also, the thickness and position of the slot. All analyses have been conducted at Re=0.45×106 and AoA=8o to simulate the take-off phase. After validation, the optimization process was conducted with two different fitness functions of Cl and L/D. According to the results, the geometry representing an optimized lift coefficient compared to the geometry with optimized L/D has a considerably higher height. Furthermore, the thickness of the slot in the first geometry is lower than the second geometry. As a result, the first optimized geometry leads to a 21.64 percent lift coefficient increment; there is a 293 percent increment in aerodynamic efficiency due to the second optimized geometry. As a result, it can be indicated that the help of slotted optimized Gurney-Flap can provide the required lift force for a short take-off landing distance.

https://mej.aut.ac.ir/article_4400_3ce3bd7d63a2c9c81983cc8e9bd02ae5.pdf

Amirkabir University of Technology Amirkabir Journal of Mechanical Engineering 2008-6032 53 11 2022 01 21 Removal of Lead Heavy Metal from Wastewater by Crystallization Process and Investigation of the Effective Parameters Removal of Lead Heavy Metal from Wastewater by Crystallization Process and Investigation of the Effective Parameters 5349 5366 4397 10.22060/mej.2021.19314.7000 FA Parvaneh Khalati Faculty of Chemical and Petroleum Engineering, University of Tabriz, Tabriz, Iran Maryam Tahmasebpour تبریز-مهندسی شیمی Seyed Jamaledin Peighambarsoust Associate Professor of Polymer Science and Engineeringو Faculty of Chemical &amp; Petroleum Engineering, University of Tabriz 0000-0001-7514-4445 Journal Article 2020 11 27 The increase in population and industrialization of societies have caused the production of large amounts of inorganic, organic, and biological pollutants. Lead is one of the heavy metals having high and long-term toxicity even at low concentrations which limits the reusability and recyclability of industrial wastewaters so it must be removed. In this study, the removal and recovery of Pb from synthetic wastewater by a new form of precipitation method named crystallization process in a batch system was investigated. This process has gained increasing attention in recent years because of accessibility, low cost, high efficiency, and no need to recover the used materials. The efficacy of removal was dependent on the factors such as pH, initial lead concentration, carbonate: lead molar ratio, and amount of seed crystals. The results of the experiments performed in this study showed that when the pH=8, the initial concentration of lead is 100 mg /L, the molar ratio of carbonate to lead is 3:1 and the amount of seed particles is 0.25 g dissolved in 100 ml, the lead removal efficiency is obtained as 99 %. The present study demonstrates that Pb can be successfully removed and recovered as PbCO3 crystals in a batch reactor. The increase in population and industrialization of societies have caused the production of large amounts of inorganic, organic, and biological pollutants. Lead is one of the heavy metals having high and long-term toxicity even at low concentrations which limits the reusability and recyclability of industrial wastewaters so it must be removed. In this study, the removal and recovery of Pb from synthetic wastewater by a new form of precipitation method named crystallization process in a batch system was investigated. This process has gained increasing attention in recent years because of accessibility, low cost, high efficiency, and no need to recover the used materials. The efficacy of removal was dependent on the factors such as pH, initial lead concentration, carbonate: lead molar ratio, and amount of seed crystals. The results of the experiments performed in this study showed that when the pH=8, the initial concentration of lead is 100 mg /L, the molar ratio of carbonate to lead is 3:1 and the amount of seed particles is 0.25 g dissolved in 100 ml, the lead removal efficiency is obtained as 99 %. The present study demonstrates that Pb can be successfully removed and recovered as PbCO3 crystals in a batch reactor.

https://mej.aut.ac.ir/article_4397_402b0702500cd47ff36e689465afd783.pdf

Amirkabir University of Technology Amirkabir Journal of Mechanical Engineering 2008-6032 53 11 2022 01 21 Passive Control of Vibrations of High-Rise Structure Using Tuned Liquid Damper under Wind and Earthquake Excitations Passive Control of Vibrations of High-Rise Structure Using Tuned Liquid Damper under Wind and Earthquake Excitations 5367 5388 4423 10.22060/mej.2021.19433.7026 FA Maziar Fahimi Farzam Department of Civil Engineering, Faculty of Engineering, University of Maragheh, Maragheh, Iran. 0000-0001-9635-8186 Babak Alinejad Department of Civil Engineering, Faculty of Engineering, University of Maragheh, Maragheh, Iran. Rasool Maroofiazar Department of Mechanical Engineering, Faculty of Engineering, University of Maragheh, Maragheh, Iran. 0000-0002-0746-4612 Hajar Kazemi Sormoli Department of Civil Engineering, Faculty of Engineering, University of Maragheh, Maragheh, Iran Journal Article 2020 12 29 One of the essential issues in structural engineering is preparing resident comfort and a sense of security for the residents of high-rise structures against earthquakes and strong winds. Therefore, the use of control systems has been considered under dynamic loads. Tuned liquid damper is an affordable and helpful device for controlling the vibrations of the structure under dynamic lateral loads. In this study, a standard high-rise structure has been modeled in ANSYS software under earthquakes (far and near-field) and wind and the interaction between wind and structure has been investigated. Tuned Liquid Damper was used to reduce the responses of the structure under far-field records (El-Centro 1940 and Hachinohe 1968), near-field records (Northridge 1994 and Kobe 1995), and wind. The responses of the structure such as displacement, velocity, acceleration, pressure, and streamline around the structure have been analyzed and also, the aerodynamic behavior of the high-rise structure against the wind has been investigated. Averagely, the results show that the Tuned Liquid Damper could reduce the maximum displacement of the structure to 16% under far-field records, 0.5% under near-field records, and 13% under the wind. One of the essential issues in structural engineering is preparing resident comfort and a sense of security for the residents of high-rise structures against earthquakes and strong winds. Therefore, the use of control systems has been considered under dynamic loads. Tuned liquid damper is an affordable and helpful device for controlling the vibrations of the structure under dynamic lateral loads. In this study, a standard high-rise structure has been modeled in ANSYS software under earthquakes (far and near-field) and wind and the interaction between wind and structure has been investigated. Tuned Liquid Damper was used to reduce the responses of the structure under far-field records (El-Centro 1940 and Hachinohe 1968), near-field records (Northridge 1994 and Kobe 1995), and wind. The responses of the structure such as displacement, velocity, acceleration, pressure, and streamline around the structure have been analyzed and also, the aerodynamic behavior of the high-rise structure against the wind has been investigated. Averagely, the results show that the Tuned Liquid Damper could reduce the maximum displacement of the structure to 16% under far-field records, 0.5% under near-field records, and 13% under the wind.

https://mej.aut.ac.ir/article_4423_b4df9f494056d51f86c7f1a89850c467.pdf

Amirkabir University of Technology Amirkabir Journal of Mechanical Engineering 2008-6032 53 11 2022 01 21 Computational Fluid Dynamics Analysis of Effects of Housing Expansion Angle, Stroke Volume and Path Length of the Fiber Bundles on Function of the Artificial Lung Computational Fluid Dynamics Analysis of Effects of Housing Expansion Angle, Stroke Volume and Path Length of the Fiber Bundles on Function of the Artificial Lung 5389 5408 4478 10.22060/mej.2021.19498.7040 FA Zahra Mollahoseini MSc/University of Tehran Bahman Vahidi Associate professor/University of Tehran 0000-0001-5597-3748 Journal Article 2021 01 13 An artificial lung can help patients waiting in line for a lung transplant or for heart bypass surgery as a respiratory aid. In this study, the incompressible and pulsatile Newtonian blood flow within a complete artificial lung model was investigated including inlet manifold, porous homogeneous medium, and outlet manifold. In this scale, the effect of variation of the expansion angle (15, 45, and 90 degrees), the stroke volume, the path length of the fibers on the artificial lung impedance was studied using computational fluid dynamics. The governing equations are discretized for a numerical solution by the finite volume method. Also, the turbulence model was selected by measuring the system impedance. In addition to the impedance, the shear stress distribution on the housing walls was investigated. The results showed that reducing the expansion angle, reducing the stroke volume, and increasing the path length of the fibers will reduce the impedance of the system. The 45-degree model has been chosen as the appropriate model. Because not only its impedance is low, but also areas with low speed flow, which can lead to clot formation, are less than the 15-degree model. In order to have lower clot formation, it is better to have the artificial lung with the natural one in series. An artificial lung can help patients waiting in line for a lung transplant or for heart bypass surgery as a respiratory aid. In this study, the incompressible and pulsatile Newtonian blood flow within a complete artificial lung model was investigated including inlet manifold, porous homogeneous medium, and outlet manifold. In this scale, the effect of variation of the expansion angle (15, 45, and 90 degrees), the stroke volume, the path length of the fibers on the artificial lung impedance was studied using computational fluid dynamics. The governing equations are discretized for a numerical solution by the finite volume method. Also, the turbulence model was selected by measuring the system impedance. In addition to the impedance, the shear stress distribution on the housing walls was investigated. The results showed that reducing the expansion angle, reducing the stroke volume, and increasing the path length of the fibers will reduce the impedance of the system. The 45-degree model has been chosen as the appropriate model. Because not only its impedance is low, but also areas with low speed flow, which can lead to clot formation, are less than the 15-degree model. In order to have lower clot formation, it is better to have the artificial lung with the natural one in series.

https://mej.aut.ac.ir/article_4478_2d3b02917ea2900fe129741a9c0f3857.pdf

Amirkabir University of Technology Amirkabir Journal of Mechanical Engineering 2008-6032 53 11 2022 01 21 Investigation of Geometric Characteristics on the Non-Reaction Supersonic Flow inside the Channel with the Presence of Cavities Investigation of Geometric Characteristics on the Non-Reaction Supersonic Flow inside the Channel with the Presence of Cavities 5409 5428 4434 10.22060/mej.2021.19574.7062 FA Vahideh Dashti Rahmat Abadi PHD Student, Malek Ashtar Uni. Mohsen A.S. Mirzabozorg Aerospace Department, Associated Professor Saeed Kheradmand Mech. Dept., MUT, Iran Journal Article 2021 02 07 In the present work, the flow inside a channel with a cavity is investigated as a Scramjet combustion chamber. For this aim, the parameters such as L/D (cavity length to cavity depth), H/D (channel height to cavity depth), and varied Mach numbers are studied in the supersonic flow to investigate the effect of geometric parameters on channel flow in non- reacting conditions. In this work, vorticity is used as a mixing parameter. Two-dimensional Navier-Stokes equations are used to solve the steady-state flow. The density based method and standard k-ε Model are employed for numerical simulation. The results show that vorticity of boundary layer and thus mixing in flow is increased with growing of L/D, Mach number and having sweep angle for the cavity. Geometries with larger H/D performed better than other geometries in terms of generating vorticity and reducing Total pressure loss. Although the H/D = 1 ratio has a higher recirculation than others, it will not be reliable for all supersonic flow because of its considerable total pressure loss and the survival of the oblique shock in some conditions. In the present work, the flow inside a channel with a cavity is investigated as a Scramjet combustion chamber. For this aim, the parameters such as L/D (cavity length to cavity depth), H/D (channel height to cavity depth), and varied Mach numbers are studied in the supersonic flow to investigate the effect of geometric parameters on channel flow in non- reacting conditions. In this work, vorticity is used as a mixing parameter. Two-dimensional Navier-Stokes equations are used to solve the steady-state flow. The density based method and standard k-ε Model are employed for numerical simulation. The results show that vorticity of boundary layer and thus mixing in flow is increased with growing of L/D, Mach number and having sweep angle for the cavity. Geometries with larger H/D performed better than other geometries in terms of generating vorticity and reducing Total pressure loss. Although the H/D = 1 ratio has a higher recirculation than others, it will not be reliable for all supersonic flow because of its considerable total pressure loss and the survival of the oblique shock in some conditions.

https://mej.aut.ac.ir/article_4434_3c8a49145944fed2bbcaade178a426c4.pdf

Amirkabir University of Technology Amirkabir Journal of Mechanical Engineering 2008-6032 53 11 2022 01 21 Experimental Investigation of a High Aspect Ratio Rectangular Liquid Jet in Parallel Airflow Experimental Investigation of a High Aspect Ratio Rectangular Liquid Jet in Parallel Airflow 5429 5444 4437 10.22060/mej.2021.19726.7096 FA Ashkan Alimehr Department of Aerospace Engineering Mehran Tadjfar Aerospace Engineering Department 0000-0002-7381-1491 Amin Jaberi Amirkabir University of Technology 0000-0001-7629-2626 Journal Article 2021 03 09 In this study, the flow dynamics of a high aspect ratio rectangular liquid jet issued into parallel airflow was experimentally investigated using a proof of concept setup, a more appropriate setup will be designed for a complete study later. The liquid flow was emanated from a rectangular injector with a thickness of 0.64 mm and an aspect ratio of 21. The injector was set in the center of the test section and the effects of airflow on the liquid flow were evaluated. A particular holding mechanism was designed and built to minimize the induced perturbations on the liquid flow. To identify the physics of the liquid flow shadowgraphy technique and high-speed imaging were implemented. In order to provide a comprehensive study of the problem, the experiments were performed for a wide range of flow conditions, and flow visualizations were presented. Jet Weber number and Gas Weber number were varied from 3 to 120 and 0.2 to 12, respectively Also, five regimes of the liquid flow including column, column/gravity, arcade, bag, and multimode were recognized. A mapping with gas Weber number and momentum ratio as the determining variables was suggested to distinguish these regimes from each other. The breakup length of the liquid jet was also measured. It was found that with the increase of jet Weber number the breakup length was increased at constant gas speed. Moreover, it was revealed that the breakup length was elongated with the increase of gas Weber number. In this study, the flow dynamics of a high aspect ratio rectangular liquid jet issued into parallel airflow was experimentally investigated using a proof of concept setup, a more appropriate setup will be designed for a complete study later. The liquid flow was emanated from a rectangular injector with a thickness of 0.64 mm and an aspect ratio of 21. The injector was set in the center of the test section and the effects of airflow on the liquid flow were evaluated. A particular holding mechanism was designed and built to minimize the induced perturbations on the liquid flow. To identify the physics of the liquid flow shadowgraphy technique and high-speed imaging were implemented. In order to provide a comprehensive study of the problem, the experiments were performed for a wide range of flow conditions, and flow visualizations were presented. Jet Weber number and Gas Weber number were varied from 3 to 120 and 0.2 to 12, respectively Also, five regimes of the liquid flow including column, column/gravity, arcade, bag, and multimode were recognized. A mapping with gas Weber number and momentum ratio as the determining variables was suggested to distinguish these regimes from each other. The breakup length of the liquid jet was also measured. It was found that with the increase of jet Weber number the breakup length was increased at constant gas speed. Moreover, it was revealed that the breakup length was elongated with the increase of gas Weber number.

https://mej.aut.ac.ir/article_4437_4bbbe6cb5982b9110413c40f3cce680b.pdf

Amirkabir University of Technology Amirkabir Journal of Mechanical Engineering 2008-6032 53 11 2022 01 21 Experimental Investigation of Thermal Performance of Pulsating Heat Pipe at Angles Close To the Horizon Experimental Investigation of Thermal Performance of Pulsating Heat Pipe at Angles Close To the Horizon 5445 5460 4462 10.22060/mej.2021.19538.7082 FA Rostam Akbari Kangarluei Department of Engineering Sciences, faculty of Tabriz, Technical and vocational University (TVU), Iran. Majid Abbasalizadeh Vice-Dean of Education, Technical Faculty, Urmia University Ahad Ramezanpour School of Engineering and the Built Environment, Anglia Ruskin University (ARU), Bishop Hall Lane, Chelmsford, Essex, UK Journal Article 2021 02 20 Pulsating heat pipes can transfer a considerable amount of heat during their simple structure and low cost. In industrial applications, one of the significant weaknesses of pulsating heat pipes is their poor performance at angles close to the horizon. Previous studies have mostly been at 90, 60, 30, and 0-degree angles and have reported the weakness of pulsating heat pipes in the 30 to zero angle range, but detailed studies have not been performed in this range. Therefore, the primary purpose of this study is to experimentally investigate the performance of pulsating heat pipes at angles of deviation close to the horizon and provide a more accurate critical inclination angle. The performance of pulsating heat pipe was evaluated for the best filling percentage (60%) at different angles 0 to 90 degrees. The results showed that by reducing the pulsating heat pipe angle from 90 degrees to 15 degrees, the difference in thermal resistance for different heat input powers was very small, but this difference increased from an angle of 10 to 0 degrees. Further studies showed that the percentage of difference in thermal resistance between angles 15, 10, and 5 with the average value of thermal resistance is 3%, 12%, and 36%, respectively. Thus, it was found that the main weakness of pulsating heat pipes is from an angle of about 10 to 0 degrees. Pulsating heat pipes can transfer a considerable amount of heat during their simple structure and low cost. In industrial applications, one of the significant weaknesses of pulsating heat pipes is their poor performance at angles close to the horizon. Previous studies have mostly been at 90, 60, 30, and 0-degree angles and have reported the weakness of pulsating heat pipes in the 30 to zero angle range, but detailed studies have not been performed in this range. Therefore, the primary purpose of this study is to experimentally investigate the performance of pulsating heat pipes at angles of deviation close to the horizon and provide a more accurate critical inclination angle. The performance of pulsating heat pipe was evaluated for the best filling percentage (60%) at different angles 0 to 90 degrees. The results showed that by reducing the pulsating heat pipe angle from 90 degrees to 15 degrees, the difference in thermal resistance for different heat input powers was very small, but this difference increased from an angle of 10 to 0 degrees. Further studies showed that the percentage of difference in thermal resistance between angles 15, 10, and 5 with the average value of thermal resistance is 3%, 12%, and 36%, respectively. Thus, it was found that the main weakness of pulsating heat pipes is from an angle of about 10 to 0 degrees.

https://mej.aut.ac.ir/article_4462_0b5e29aa1acf8bdc5d8935d7036fa4f5.pdf

Amirkabir University of Technology Amirkabir Journal of Mechanical Engineering 2008-6032 53 11 2022 01 21 Numerical Study of Natural Convection Heat Transfer inside a Triangular Cavity with Flexible Sidewalls Containing a Cylindrical Heat Source Numerical Study of Natural Convection Heat Transfer inside a Triangular Cavity with Flexible Sidewalls Containing a Cylindrical Heat Source 5461 5484 4466 10.22060/mej.2021.19669.7087 FA Adel Chidan Department of Mechanical Engineering, shahrekord University Afrasiab Raisi Engineering Faculty, Shahrekord University, Shahrekord, PO Box 115, Iran 0000-0003-3748-7839 Behzad Ghasemi Department of Mechanical Engineering, shahrekord University Journal Article 2021 02 24 In this study, the natural convection heat transfer within a triangular cavity with elastic diagonal walls containing a cylindrical heat source is investigated. The assumed fluid inside the cavity is air. The flexible diagonal walls of the cavity are considered to be at a constant cold temperature of Tc and the cylindrical heat source is at the hot temperature of Th. In this study, the interaction of fluid and solid fields and the effect of cylindrical heat source position on flow and temperature fields are examined. For this purpose, the effect of Rayleigh number and changing the position of the heat source along the vertical centerline on the deformation of flexible walls, flow and temperature fields, and heat transfer rate are investigated. The results show that for a fixed position of the heat source, an increase in the Rayleigh number increases the maximum of the stream function, the average Nusselt number, and the deformation of the flexible walls. Also, the results show that the position of the heat source depending on the Rayleigh number has different effects on the temperature and flow fields. As the heat source moves to the bottom of the cavity, the average Nusselt number for Rayleigh numbers of 104 and 105 decreases, and Rayleigh number of 106 first increases and then decreases. In this study, the natural convection heat transfer within a triangular cavity with elastic diagonal walls containing a cylindrical heat source is investigated. The assumed fluid inside the cavity is air. The flexible diagonal walls of the cavity are considered to be at a constant cold temperature of Tc and the cylindrical heat source is at the hot temperature of Th. In this study, the interaction of fluid and solid fields and the effect of cylindrical heat source position on flow and temperature fields are examined. For this purpose, the effect of Rayleigh number and changing the position of the heat source along the vertical centerline on the deformation of flexible walls, flow and temperature fields, and heat transfer rate are investigated. The results show that for a fixed position of the heat source, an increase in the Rayleigh number increases the maximum of the stream function, the average Nusselt number, and the deformation of the flexible walls. Also, the results show that the position of the heat source depending on the Rayleigh number has different effects on the temperature and flow fields. As the heat source moves to the bottom of the cavity, the average Nusselt number for Rayleigh numbers of 104 and 105 decreases, and Rayleigh number of 106 first increases and then decreases.

https://mej.aut.ac.ir/article_4466_4e46e93a054f94c059e1fa4701f5a892.pdf

Amirkabir University of Technology Amirkabir Journal of Mechanical Engineering 2008-6032 53 11 2022 01 21 Numerical Investigation of Hybrid Wick Structure Effect on Thermal Performance of a Thin Flat Heat Pipe Numerical Investigation of Hybrid Wick Structure Effect on Thermal Performance of a Thin Flat Heat Pipe 5485 5504 4465 10.22060/mej.2021.19721.7095 FA Gholamreza Abdizadeh Department of Aerospace Engineering, Amirkabir University of Technology, Tehran, Iran Sahar Noori Hamid Reza Tajik Satellite Research Institute, Iranian Space Research Center, Tehran, Iran Mehran Shahryari Satellite Research Institute, Iranian Space Research Center, Tehran, Iran Mohammad Saeedi Assistant Professor, Department of Aerospace Engineering, Amirkabir University of Technology, Tehran, Iran Journal Article 2021 03 08 Due to the volume and mass limits of the small electronic devices, thin flat heat pipes are an ideal solution for the efficient transfer and dissipation of heat. The performance of thin heat pipes is heavily dependent on wick structure characteristics. In this research, the thermal performance of thin flat heat pipes with hybrid and grooved wick for different heat inputs were studied numerically, and their heat transfer characteristics were compared. The trends of various parameters such as wall temperature, maximum axial velocity, mass transfer at the liquid-vapor interface, system pressure, and thermal resistance on the thermal performance of the thin flat heat pipe with hybrid and groove wicks were analyzed. The numerical simulation has been done using a two‐dimensional unsteady incompressible laminar flow. Results indicated that the evaporation section temperature of hybrid wick thin flat heat pipe is significantly lower than the corresponding value of grooves heat pipe. It was also observed that with increasing heat input, the thermal resistance of hybrid wick thin flat heat pipe decreased and it has excellent performance compared to the grooved wick. For heat fluxes of 10, 20, and 30 W, the performance of the thin flat heat pipe with hybrid wick compared to grooved wick is improved by 3.59%, 20.38%, and 28.57%, respectively. Therefore, the thermal performance improvement of the thin flat heat pipe with the hybrid wick was more significant. This improvement is more considerable for higher heat fluxes. Due to the volume and mass limits of the small electronic devices, thin flat heat pipes are an ideal solution for the efficient transfer and dissipation of heat. The performance of thin heat pipes is heavily dependent on wick structure characteristics. In this research, the thermal performance of thin flat heat pipes with hybrid and grooved wick for different heat inputs were studied numerically, and their heat transfer characteristics were compared. The trends of various parameters such as wall temperature, maximum axial velocity, mass transfer at the liquid-vapor interface, system pressure, and thermal resistance on the thermal performance of the thin flat heat pipe with hybrid and groove wicks were analyzed. The numerical simulation has been done using a two‐dimensional unsteady incompressible laminar flow. Results indicated that the evaporation section temperature of hybrid wick thin flat heat pipe is significantly lower than the corresponding value of grooves heat pipe. It was also observed that with increasing heat input, the thermal resistance of hybrid wick thin flat heat pipe decreased and it has excellent performance compared to the grooved wick. For heat fluxes of 10, 20, and 30 W, the performance of the thin flat heat pipe with hybrid wick compared to grooved wick is improved by 3.59%, 20.38%, and 28.57%, respectively. Therefore, the thermal performance improvement of the thin flat heat pipe with the hybrid wick was more significant. This improvement is more considerable for higher heat fluxes.

https://mej.aut.ac.ir/article_4465_30da227c6b5b9e2482b6b221c711edfd.pdf

Amirkabir University of Technology Amirkabir Journal of Mechanical Engineering 2008-6032 53 11 2022 01 21 Network Modeling to Investigate the Effect of Coupling the Transport Phenomena on Water Distribution in Gas Diffusion Layer Network Modeling to Investigate the Effect of Coupling the Transport Phenomena on Water Distribution in Gas Diffusion Layer 5505 5528 4314 10.22060/mej.2021.19340.7004 FA Hamed Gholipour Mechanical engineering department, Amirkabir university of technology, Tehran, Iran Mohammad J. Kermani Mechanical engineering department, Amirkabir university of technology, Tehran, Iran Rahim Zamanian New Technologies Research Center, Amirkabir University of Technology, Tehran, Iran Journal Article 2020 12 04 The cathode side gas diffusion layer in polymer electrolyte membrane fuel cells discharges out the water generated as a result of the electrochemical reaction through its porous medium. This paper criticizes the generated pore network models for gas diffusion layers assuming uniform injection of liquid water from the catalyst layer. These models lead to a roughly uniform distribution of liquid water saturation in the in-plane direction making no difference between under gas channel and under rib regions which is in contradiction with the in-situ visualizations of gas diffusion layers. It has been attempted in this paper to couple the existing two-phase flow network models to other transport phenomena in the gas diffusion layer and also in other layers. To achieve this, the mentioned model is coupled to network models of oxygen and electron transport at the cathode side and also to a model of electrochemical reaction at the catalyst layer and a proton transport model of the membrane. As the first result of modeling, the distribution of local water generation rate and also the temporal evolution of total water generation rate at catalyst layer are presented, the latter experiencing an approximate 50% reduction from start-up to steady-state. The resulting water saturation distribution is strongly non-uniform, and maximums are observed under the ribs which is a direct result of non-uniform water generation at reaction sites. The cathode side gas diffusion layer in polymer electrolyte membrane fuel cells discharges out the water generated as a result of the electrochemical reaction through its porous medium. This paper criticizes the generated pore network models for gas diffusion layers assuming uniform injection of liquid water from the catalyst layer. These models lead to a roughly uniform distribution of liquid water saturation in the in-plane direction making no difference between under gas channel and under rib regions which is in contradiction with the in-situ visualizations of gas diffusion layers. It has been attempted in this paper to couple the existing two-phase flow network models to other transport phenomena in the gas diffusion layer and also in other layers. To achieve this, the mentioned model is coupled to network models of oxygen and electron transport at the cathode side and also to a model of electrochemical reaction at the catalyst layer and a proton transport model of the membrane. As the first result of modeling, the distribution of local water generation rate and also the temporal evolution of total water generation rate at catalyst layer are presented, the latter experiencing an approximate 50% reduction from start-up to steady-state. The resulting water saturation distribution is strongly non-uniform, and maximums are observed under the ribs which is a direct result of non-uniform water generation at reaction sites.

https://mej.aut.ac.ir/article_4314_2bf7e9e8f3f3bce1ac5212f22414aa57.pdf

Amirkabir University of Technology Amirkabir Journal of Mechanical Engineering 2008-6032 53 11 2022 01 21 Energy Analysis and Exergy of the System of Simultaneous Production of Power and Hydrogen with the Excitatory Gasification of Municipal Solid Waste Energy Analysis and Exergy of the System of Simultaneous Production of Power and Hydrogen with the Excitatory Gasification of Municipal Solid Waste 5529 5550 4365 10.22060/mej.2021.19446.7029 FA Amirhamzeh Farajollahi Department of Engineering, Imam Ali University, Tehran, Iran 0000-0001-9201-1871 Amirhossein Hejazi Babol Noshirvani University of Technology Heshmat Gazori Imam Ali university Mohsen Rostami ]ئشئ َمه دهرثقسهفغuniversity,Tehran,Iran Journal Article 2021 01 02 Nowadays, due to the extensive application of renewable-based cogeneration systems and also the economic and environmental necessities, their design and thermodynamic analysis have been conducted by many scientists. In this way, a novel, simple, and practical combined power and hydrogen cogeneration unit have been designed in the present study in which there are gas turbine, gasifier, transcritical Rankine cycle, and proton exchange membrane electrolyzer. This system has been analyzed from the first and second laws of thermodynamics by an engineering equation solver. The proposed system is able to generate power and hydrogen simultaneously for users. The power and hydrogen production capacities of the system are 3.92 MW and 608.8 cubic meters per hour, respectively, which consume biomass of about 1.155 kg/s. The energy utilization factor and exergy efficiency of the system is 34.71 % and 29.44 %, respectively. It can be seen that the overall exergy destruction of the system is 11854 kW, in which gasifier, gas turbine, and combustion chamber have the highest irreversibilities. In addition, it can be concluded that the exergy efficiency of condenser and heat exchanger 3 are the lowest ones among other types of equipment. According to the parametric studies, it was found that increasing the inlet temperature of the gas turbine has a positive effect, and increasing the maximum pressure of the transcritical carbon dioxide cycle has a negative effect on the energy utilization factor and the exergy efficiency of the system. Nowadays, due to the extensive application of renewable-based cogeneration systems and also the economic and environmental necessities, their design and thermodynamic analysis have been conducted by many scientists. In this way, a novel, simple, and practical combined power and hydrogen cogeneration unit have been designed in the present study in which there are gas turbine, gasifier, transcritical Rankine cycle, and proton exchange membrane electrolyzer. This system has been analyzed from the first and second laws of thermodynamics by an engineering equation solver. The proposed system is able to generate power and hydrogen simultaneously for users. The power and hydrogen production capacities of the system are 3.92 MW and 608.8 cubic meters per hour, respectively, which consume biomass of about 1.155 kg/s. The energy utilization factor and exergy efficiency of the system is 34.71 % and 29.44 %, respectively. It can be seen that the overall exergy destruction of the system is 11854 kW, in which gasifier, gas turbine, and combustion chamber have the highest irreversibilities. In addition, it can be concluded that the exergy efficiency of condenser and heat exchanger 3 are the lowest ones among other types of equipment. According to the parametric studies, it was found that increasing the inlet temperature of the gas turbine has a positive effect, and increasing the maximum pressure of the transcritical carbon dioxide cycle has a negative effect on the energy utilization factor and the exergy efficiency of the system.

https://mej.aut.ac.ir/article_4365_d3e0f226df6865b28fb677548370f467.pdf

Amirkabir University of Technology Amirkabir Journal of Mechanical Engineering 2008-6032 53 11 2022 01 21 Thermo-Economic Evaluation of a Power and Freshwater Production System Including a Liquid Metal Magnetohydrodynamic Unit Driven By a Concentrated Solar Tower and Biogas Thermo-Economic Evaluation of a Power and Freshwater Production System Including a Liquid Metal Magnetohydrodynamic Unit Driven By a Concentrated Solar Tower and Biogas 5551 5572 4396 10.22060/mej.2021.19495.7039 FA Qasem Abdollah Nezhad Department of Mechanical Engineering, Urmia University, Urmia, Iran. Samad Jafarmadar Department of Mechanical Engineering, Urmia University, Urmia, Iran. Shahram Khalilarya Department of Mechanical Engineering, Urmia University, Urmia, Iran. 0000-0002-6434-852X Journal Article 2021 01 13 The use of liquid metal magnetic hydrodynamic energy units, despite reducing maintenance costs and improving reliability, requires a high-temperature source, which must be supplied by fossil fuels. The present study aims to cover this shortage by proposing a new design for liquid metal magnetic hydrodynamic power and desalination cogeneration plant by applying concentrating solar power. The results show that 73.2 kW and 21.06 m3/day power and fresh water can be produced by the proposed cogeneration plant, respectively. The energy utilization factor and total exergy efficiency are 97.45 and 26.34%. The results also indicate that the receiver accounts for the highest exergy destruction, followed by the heliostat with 270.4 kW and 240.9 kW, respectively. Increasing the efficiency of the humidifier/dehumidifier or reducing the mass flow rate of the second magnetic hydrodynamic loop improves the energetic and exergetic performances of the system. Besides, the receiver and solar tower have the highest cost of investment and maintenance, and the total unit cost of the system is 103.4 $/GJ. The use of liquid metal magnetic hydrodynamic energy units, despite reducing maintenance costs and improving reliability, requires a high-temperature source, which must be supplied by fossil fuels. The present study aims to cover this shortage by proposing a new design for liquid metal magnetic hydrodynamic power and desalination cogeneration plant by applying concentrating solar power. The results show that 73.2 kW and 21.06 m3/day power and fresh water can be produced by the proposed cogeneration plant, respectively. The energy utilization factor and total exergy efficiency are 97.45 and 26.34%. The results also indicate that the receiver accounts for the highest exergy destruction, followed by the heliostat with 270.4 kW and 240.9 kW, respectively. Increasing the efficiency of the humidifier/dehumidifier or reducing the mass flow rate of the second magnetic hydrodynamic loop improves the energetic and exergetic performances of the system. Besides, the receiver and solar tower have the highest cost of investment and maintenance, and the total unit cost of the system is 103.4 $/GJ.

https://mej.aut.ac.ir/article_4396_b4aa00bc1c59b9d1cdd07479070e355e.pdf

Amirkabir University of Technology Amirkabir Journal of Mechanical Engineering 2008-6032 53 11 2022 01 21 Investigating the Effects of Loung Chair Fire in a Cinema Hall Using Displacement, Impingement Jet and Stratum Ventilation Systems Investigating the Effects of Loung Chair Fire in a Cinema Hall Using Displacement, Impingement Jet and Stratum Ventilation Systems 5573 5594 4492 10.22060/mej.2021.19681.7089 FA Mostafa Ramezani Semnan University Amir Mohammad Jadidi Assistant professor of mechanical engineering, Semnan university,Semnan, Iran Roholah Rafee Faculty of Mechanical Engineering, Semnan University Journal Article 2021 02 27 In this article, the effects of burning a chair in a cinema hall have been investigated by using displacement, impingement jet, and stratum ventilation systems. The most important results of this study by comparing displacement ventilation, impingement jet ventilation, and stratum ventilation is that displacement ventilation and impingement jet ventilation could decrease soot of fire by 31%, carbon dioxide 16%, and carbon monoxide 11% better than other systems. The concentration of toxic gases from the fire in all three systems is within the permissible and safe range in a way that the two systems of displacement ventilation and impingement jet ventilation recorded 6.3 ppm and 7.5 ppm for carbon monoxide respectively. In the case of carbon dioxide gas, two systems of displacement ventilation and impingement jet have decreased CO2 to 330 ppm and 370 ppm respectively. In controlling the heat exhaust from the doors of the cinema hall, displacement ventilation and impingement jet ventilation in door 1 are 66.6% better than stratum ventilation and in door 2 the impingement jet system is 96% better than the stratum ventilation system. In this article, the effects of burning a chair in a cinema hall have been investigated by using displacement, impingement jet, and stratum ventilation systems. The most important results of this study by comparing displacement ventilation, impingement jet ventilation, and stratum ventilation is that displacement ventilation and impingement jet ventilation could decrease soot of fire by 31%, carbon dioxide 16%, and carbon monoxide 11% better than other systems. The concentration of toxic gases from the fire in all three systems is within the permissible and safe range in a way that the two systems of displacement ventilation and impingement jet ventilation recorded 6.3 ppm and 7.5 ppm for carbon monoxide respectively. In the case of carbon dioxide gas, two systems of displacement ventilation and impingement jet have decreased CO2 to 330 ppm and 370 ppm respectively. In controlling the heat exhaust from the doors of the cinema hall, displacement ventilation and impingement jet ventilation in door 1 are 66.6% better than stratum ventilation and in door 2 the impingement jet system is 96% better than the stratum ventilation system.

https://mej.aut.ac.ir/article_4492_88f0bf2899c595146bff13b20342eb6a.pdf

Amirkabir University of Technology Amirkabir Journal of Mechanical Engineering 2008-6032 53 11 2022 01 21 Simulation of Effective Parameters on Desalination Water Using Capacitive Deionization Method Simulation of Effective Parameters on Desalination Water Using Capacitive Deionization Method 5595 5612 4438 10.22060/mej.2021.19769.7104 FA Abolghasem Abolghasemi Master of Science Student, Department of Mechanical Engineering, K. N. Toosi University of Technology, Tehran, Iran Sadegh Seddighi Assistant Professor, Department of Mechanical Engineering, K. N. Toosi University of Technology, Tehran, Iran Journal Article 2021 03 19 Capacitive ionization is one of the membrane methods available for water desalination that works based on ion exchange. In capacitive ionization systems, saline water passes through a cell that has electrodes with a high contact surface. By applying a voltage, the ions are absorbed under an electric field on the surface of the porous electrodes, as a result of which the salinity of the water is reduced and freshwater is removed from the other side of the system. Recently, researchers have proposed various models for predicting the behavior of desalination plants by capacitive deionization. The model used for the simulation is a one-dimensional transfer equation based on the transfer theory of porous and ball-Chapman-Stern electrodes to predict the output water concentration and identify the parameters affecting the performance of the capacitive ionization system. This study aimed to investigate the water desalination efficiency using changes in the operating parameters of capacitive ionization systems. The parameters studied in this study included fluid flow, applied electric current, input concentration, porosity, electrode cross-section, and electrode length. The results showed that the most effective parameter in improving the performance of the device is applied electric current so that with a fifty percent increase in applied electric current, the percentage of water desalination increased by about 72%, and the time required to achieve maximum water desalination decreased by about 76%. Capacitive ionization is one of the membrane methods available for water desalination that works based on ion exchange. In capacitive ionization systems, saline water passes through a cell that has electrodes with a high contact surface. By applying a voltage, the ions are absorbed under an electric field on the surface of the porous electrodes, as a result of which the salinity of the water is reduced and freshwater is removed from the other side of the system. Recently, researchers have proposed various models for predicting the behavior of desalination plants by capacitive deionization. The model used for the simulation is a one-dimensional transfer equation based on the transfer theory of porous and ball-Chapman-Stern electrodes to predict the output water concentration and identify the parameters affecting the performance of the capacitive ionization system. This study aimed to investigate the water desalination efficiency using changes in the operating parameters of capacitive ionization systems. The parameters studied in this study included fluid flow, applied electric current, input concentration, porosity, electrode cross-section, and electrode length. The results showed that the most effective parameter in improving the performance of the device is applied electric current so that with a fifty percent increase in applied electric current, the percentage of water desalination increased by about 72%, and the time required to achieve maximum water desalination decreased by about 76%.

https://mej.aut.ac.ir/article_4438_b0a665a28efd91535abb111d656ecd04.pdf