Amirkabir University of Technology Amirkabir Journal of Mechanical Engineering 2008-6032 54 1 2022 03 21 Numerical Investigation on the Fluid Elasticity Effect in the Impact of Oblique Drop onto Liquid Film Numerical Investigation on the Fluid Elasticity Effect in the Impact of Oblique Drop onto Liquid Film 3 30 4576 10.22060/mej.2021.19488.7036 FA Mohammad Reza Rezaie Mechanical Engineering Department, Shahrood university of Technology, Shahrood, Iran Mahmood Norouzi Faculty of Mechanical Engineering, Shahrood University of Technology, Shahrood, Iran Mohammad Hassan Kayhani Mechanical Engineering Department, Shahrood University of Technology, Shahrood, Iran Seyed Mohammad Taghavi Chemical Engineering Department, Laval University, Quebec, Canada Journal Article 2021 01 12 In this paper, the crown formation and temporal propagation due to the oblique impact of a plane two-dimensional drop onto preexisting film in the non-Newtonian viscoelastic fluid are analyzed numerically. The finite volume method is applied to solve the governing equations and the volume of fluid technique is used to track the free surface of liquid phases. Here, the well-known Oldroyd-B model is used as the constitutive equation for the viscoelastic phase. However, the formation and temporal evolution of the crown’s shape is emphasized and the effects of elastic and surface tension forces on the crown’s dynamic are considered in detail. The results show that the increase in Weissenberg number, viscosity ratio, and Weber number leads to an increase in both the dimensionless crown height (Z*) and spread factor (S*), while impact angle has a major effect on the control of the crown’s height, on the other hand, this parameter has a negligible effect on spread factor in viscoelastic fluid. Moreover, by thickening of fluid film, the crown’s height increase, and the crown’s radius decrease. As the main finding of the present study, the fluid’s elasticity in the presence of surface tension force can enhance the rate of the crown propagation in the impact of an oblique drop onto liquid film. In this paper, the crown formation and temporal propagation due to the oblique impact of a plane two-dimensional drop onto preexisting film in the non-Newtonian viscoelastic fluid are analyzed numerically. The finite volume method is applied to solve the governing equations and the volume of fluid technique is used to track the free surface of liquid phases. Here, the well-known Oldroyd-B model is used as the constitutive equation for the viscoelastic phase. However, the formation and temporal evolution of the crown’s shape is emphasized and the effects of elastic and surface tension forces on the crown’s dynamic are considered in detail. The results show that the increase in Weissenberg number, viscosity ratio, and Weber number leads to an increase in both the dimensionless crown height (Z*) and spread factor (S*), while impact angle has a major effect on the control of the crown’s height, on the other hand, this parameter has a negligible effect on spread factor in viscoelastic fluid. Moreover, by thickening of fluid film, the crown’s height increase, and the crown’s radius decrease. As the main finding of the present study, the fluid’s elasticity in the presence of surface tension force can enhance the rate of the crown propagation in the impact of an oblique drop onto liquid film.

https://mej.aut.ac.ir/article_4576_f89394c979b34a25cc4ff8e11234fbfb.pdf

Amirkabir University of Technology Amirkabir Journal of Mechanical Engineering 2008-6032 54 1 2022 03 21 Finite Element Modeling of Fluid-Solid-Piezoelectric for Investigating the Ways of Improving the Performance of the Micro Energy Harvester in the Fluid Flow Finite Element Modeling of Fluid-Solid-Piezoelectric for Investigating the Ways of Improving the Performance of the Micro Energy Harvester in the Fluid Flow 31 54 4557 10.22060/mej.2021.19490.7037 FA Masoomeh Salari دانشکده مهندسی مکانیک Hamed Afrasiab Assistant Professor, Mechanical Engineering Department, Babol Noshirvani University of Technology, Babol, Iran Mohammad Hadi Pashaei Associate Professor, Faculty of Mechanical Engineering, Babol Noshirvani University of Technology, Babol, Iran Reza Akbari Alashti دانشکده مهندسی مکانیک Journal Article 2021 01 12 A coupled fluid-solid-piezoelectric model has been developed by finite element method to study and improve the performance of a micro piezoelectric transducer designed for fluid flow energy harvesting. In this harvester, when the turbulence flow of water passes over a bluff body, the vortex shedding phenomenon occurs and applies a periodical lift force to a piezoelectric beam placed in the downstream region. The resulting oscillations in the piezoelectric beam lead to electrical power generation. Navier-Stokes equations and large-eddy simulation method have been used to describe the fluid turbulence flow, and equations of conservation of linear momentum along with piezoelectric constitutive relations have been employed to obtain solid deformation and electric field intensity. Numerical experiments designed by Taguchi’s method have been used to study the effect of different parameters on the harvester performance. The results have shown that using a triangular or D-shape bluff body, and selecting the minimum possible values for the length to height ratio of the bluff body, the distance between the beam and the bluff body, and eccentricity of the beam relative to the bluff body is beneficial for better performance. Furthermore, the shape of the bluff body has been the most influential parameter on the harvester performance. A coupled fluid-solid-piezoelectric model has been developed by finite element method to study and improve the performance of a micro piezoelectric transducer designed for fluid flow energy harvesting. In this harvester, when the turbulence flow of water passes over a bluff body, the vortex shedding phenomenon occurs and applies a periodical lift force to a piezoelectric beam placed in the downstream region. The resulting oscillations in the piezoelectric beam lead to electrical power generation. Navier-Stokes equations and large-eddy simulation method have been used to describe the fluid turbulence flow, and equations of conservation of linear momentum along with piezoelectric constitutive relations have been employed to obtain solid deformation and electric field intensity. Numerical experiments designed by Taguchi’s method have been used to study the effect of different parameters on the harvester performance. The results have shown that using a triangular or D-shape bluff body, and selecting the minimum possible values for the length to height ratio of the bluff body, the distance between the beam and the bluff body, and eccentricity of the beam relative to the bluff body is beneficial for better performance. Furthermore, the shape of the bluff body has been the most influential parameter on the harvester performance.

https://mej.aut.ac.ir/article_4557_3596c80a46918e6dde2f3c37290cba47.pdf

Amirkabir University of Technology Amirkabir Journal of Mechanical Engineering 2008-6032 54 1 2022 03 21 Numerical Investigation of Flow Structure and Performance of Centrifugal Pump with Cavitation Numerical Investigation of Flow Structure and Performance of Centrifugal Pump with Cavitation 55 74 4582 10.22060/mej.2021.19794.7115 FA Sarallah Abbasi assistant professor, Arak university of technology Hasan Gholizadeh Arak university of technology Journal Article 2021 03 26 In the present paper, the numerical simulation of the flow to identify the cavitation and its effects inside the centrifugal pump of 100-250 type of Pumpiran Company, including the impeller and volute of the pump, has been done. The Rayleigh–Plesset equation was employed to study the growth and collapse of the vapor bubble. In order to validate the numerical results, the pump curves were extracted from the present study and compared with similar experimental. The deviation of the present numerical results with the experimental ones in the pump design flow rate is 6.5%. It is found that cavitation occurs at inlet pressures of less than 45 kPa. By reducing the inlet pressure from 40 kPa to 20 kPa, the flow separation rate also increases and its position is transferred from the beginning of the blade to the inner areas of the blade. The position of cavitation occurs at 0.14 to 0.24 of the passage as well as at the beginning of the blades. The volume fraction of steam in these parts has increased from 0.04 to 0.96, respectively. With cavitation in the net positive suction head equal to 1.52, a 3% drop of the head is observed in the diagrams. In the present paper, the numerical simulation of the flow to identify the cavitation and its effects inside the centrifugal pump of 100-250 type of Pumpiran Company, including the impeller and volute of the pump, has been done. The Rayleigh–Plesset equation was employed to study the growth and collapse of the vapor bubble. In order to validate the numerical results, the pump curves were extracted from the present study and compared with similar experimental. The deviation of the present numerical results with the experimental ones in the pump design flow rate is 6.5%. It is found that cavitation occurs at inlet pressures of less than 45 kPa. By reducing the inlet pressure from 40 kPa to 20 kPa, the flow separation rate also increases and its position is transferred from the beginning of the blade to the inner areas of the blade. The position of cavitation occurs at 0.14 to 0.24 of the passage as well as at the beginning of the blades. The volume fraction of steam in these parts has increased from 0.04 to 0.96, respectively. With cavitation in the net positive suction head equal to 1.52, a 3% drop of the head is observed in the diagrams.

https://mej.aut.ac.ir/article_4582_f1298750ed09618717f9c10ea8d1d3b0.pdf

Amirkabir University of Technology Amirkabir Journal of Mechanical Engineering 2008-6032 54 1 2022 03 21 Characterization of the Effect of Helicopter Isolated Blade Vortex on Dynamic Stall Characterization of the Effect of Helicopter Isolated Blade Vortex on Dynamic Stall 75 100 4604 10.22060/mej.2021.19805.7124 FA Farid Hosseinzadeh Esfahani Department of Aerospace Engineering, Amirkabir University of Technology, Tehran, Iran 0009-0003-3893-1169 Seyed Mohammad Hossein Karimian Department of Aerospace Engineering, Amirkabir University of Technology, Tehran, Iran 0000-0002-1934-7413 Hamid Parhizkar Department of Aerospace Engineering, Malek Ashtar University of Technology, Tehran, Iran Journal Article 2021 04 05 In this research, dynamic stall at sections near the rotor blade tip at a maximum cruise speed of the helicopter with an advanced ratio of 0.35 and cyclic pitching motion, has been studied using computational fluid dynamics simulation. Unsteady Reynolds-averaged Navier–Stokes equations are solved using model on a domain discretized into a hybrid mesh using finite volume discretization method. Numerical simulation is validated using experimental results of AH1-G helicopter flight tests. Comparison of results indicates that present numerical results match with experimental data well. Dynamic stall occurs as a result of a shock wave in the advancing side which affects the lift coefficient. Interestingly, the effect of the shock wave on the lift coefficient in the regions closer to the blade tip is weakened due to the tip vortex penetration. As a result, few changes are seen in the lift coefficient in these regions in comparison to those of the inner regions of the blade. In addition, the maximum value of lift coefficient in the section closer to the blade tip reduces by 10.2% in comparison to that of the most inner section. Results show that despite the formation of the leading-edge vortex, especially in the inner most sections of the blade, severe dynamic stall does not occur in the retreating side. In fact, this is due to the weakening of the leading edge vortex by the effect of the radial flow. In this research, dynamic stall at sections near the rotor blade tip at a maximum cruise speed of the helicopter with an advanced ratio of 0.35 and cyclic pitching motion, has been studied using computational fluid dynamics simulation. Unsteady Reynolds-averaged Navier–Stokes equations are solved using model on a domain discretized into a hybrid mesh using finite volume discretization method. Numerical simulation is validated using experimental results of AH1-G helicopter flight tests. Comparison of results indicates that present numerical results match with experimental data well. Dynamic stall occurs as a result of a shock wave in the advancing side which affects the lift coefficient. Interestingly, the effect of the shock wave on the lift coefficient in the regions closer to the blade tip is weakened due to the tip vortex penetration. As a result, few changes are seen in the lift coefficient in these regions in comparison to those of the inner regions of the blade. In addition, the maximum value of lift coefficient in the section closer to the blade tip reduces by 10.2% in comparison to that of the most inner section. Results show that despite the formation of the leading-edge vortex, especially in the inner most sections of the blade, severe dynamic stall does not occur in the retreating side. In fact, this is due to the weakening of the leading edge vortex by the effect of the radial flow.

https://mej.aut.ac.ir/article_4604_d630553e32ae21fb1a6df39c702d2c5c.pdf

Amirkabir University of Technology Amirkabir Journal of Mechanical Engineering 2008-6032 54 1 2022 03 21 Investigation of Electro-Osmotic Micro-Pumps Using Electrical Field Gradient and Asymmetric Micro-Electrodes: Numerical Modeling and Experimental Validation Investigation of Electro-Osmotic Micro-Pumps Using Electrical Field Gradient and Asymmetric Micro-Electrodes: Numerical Modeling and Experimental Validation 101 122 4547 10.22060/mej.2021.19841.7129 FA Tannaz Tavari SUT Mohsen Nazari Pooria Akbarzadeh SUT Naser Sepehry SUT Mostafa Nazari Department of Mechanical Engineering, Shahrood University of Technology, Shahrood, Iran. Journal Article 2021 04 09 In the present study, in order to fabricate AC electroosmotic micropumps, the improvement of geometrical parameters of the 3D electrode, such as width, height, and location of 3D steps on the base electrodes in one pair, the base electrodes size (symmetric or asymmetric), electrodes gap, and also electrical characteristics including voltage and frequency have been investigated. Also, the fluid flow (KCl) in the channel was analyzed. The governing equations of fluid flow and electrical domain have been solved using the finite element method to investigate the effect of electrode geometry on slip velocity, which affects the fluid flow. In order to validate our numerical simulation, this chip is fabricated by photolithography method such as deposition of platinum electrodes, creating 3D steps on the base electrodes using a polymer, and fabrication of a microchannel. Finally, Our results indicate that an optimal design results in a pump with the width (50 µm) and steps height (5 µm) of each electrode and their displacement (30 µm) are capable of generating a high velocity, flow rate, and pressure around 1.77 mm/s, 14.9 ml/min and 74.6 Pa, respectively at a given voltage (2.5 V) and frequency (1 kHz), which qualitatively matches the trend observed in the experiment. This design provides an improvement in electroosmotic pumping. In the present study, in order to fabricate AC electroosmotic micropumps, the improvement of geometrical parameters of the 3D electrode, such as width, height, and location of 3D steps on the base electrodes in one pair, the base electrodes size (symmetric or asymmetric), electrodes gap, and also electrical characteristics including voltage and frequency have been investigated. Also, the fluid flow (KCl) in the channel was analyzed. The governing equations of fluid flow and electrical domain have been solved using the finite element method to investigate the effect of electrode geometry on slip velocity, which affects the fluid flow. In order to validate our numerical simulation, this chip is fabricated by photolithography method such as deposition of platinum electrodes, creating 3D steps on the base electrodes using a polymer, and fabrication of a microchannel. Finally, Our results indicate that an optimal design results in a pump with the width (50 µm) and steps height (5 µm) of each electrode and their displacement (30 µm) are capable of generating a high velocity, flow rate, and pressure around 1.77 mm/s, 14.9 ml/min and 74.6 Pa, respectively at a given voltage (2.5 V) and frequency (1 kHz), which qualitatively matches the trend observed in the experiment. This design provides an improvement in electroosmotic pumping.

https://mej.aut.ac.ir/article_4547_3910d2e3adfd0dc2e3a048f15c11eb74.pdf

Amirkabir University of Technology Amirkabir Journal of Mechanical Engineering 2008-6032 54 1 2022 03 21 Experimental Study of Aerodynamic Behavior of NACA0012 Airfoil near the Surface Experimental Study of Aerodynamic Behavior of NACA0012 Airfoil near the Surface 123 144 4476 10.22060/mej.2021.19844.7130 FA Mostafa Hadidoolabi Malek Ashtar University of Technology, Tehran, Iran Mahdi Bakhtiari Fasr Malek Ashtar University of Technology, Tehran, Iran 0000-0002-2788-1317 Seyed Hoseyn Sadati Malek Ashtar University of Technology, Tehran, Iran Journal Article 2021 04 09 When a flying vehicle approaches a surface of water or land, changes occur in the pattern of the fluid flow field around it. This change in flow field eliminates the direct effect on aerodynamics and control of the vehicle. This is more common when the vehicle is landing and taking off, as well as flying at low altitudes, which is called the surface effect. In this research, the phenomenon of surface effect and its effect on aerodynamic coefficients and flow pattern around NACA0012 airfoil in the static incompressible subsonic regime have been investigated numerically and experimentally. Experimental tests were performed in the incompressible subsonic wind tunnel of the Ghadr National Aerodynamics Research Center of Imam Hossein University with a cross-sectional area of 80 by 100 cm. The simulation of the phenomenon is a fixed ground with the minimum possible thickness of the boundary layer in the wind tunnel. Solve the flow field numerically based on Navier Stokes equations along with the Transition-SST viscous model. The impact of the surface effect phenomenon on the change of aerodynamic coefficients has been investigated by considering different distances from the surface in the static state. The pressure distribution on the airfoil surface is measured by an accurate pressure sensor and is due to the surface effect phenomenon at close distances to the surface. The results of the static analysis show an increase in lift force and a decrease in drag force. When a flying vehicle approaches a surface of water or land, changes occur in the pattern of the fluid flow field around it. This change in flow field eliminates the direct effect on aerodynamics and control of the vehicle. This is more common when the vehicle is landing and taking off, as well as flying at low altitudes, which is called the surface effect. In this research, the phenomenon of surface effect and its effect on aerodynamic coefficients and flow pattern around NACA0012 airfoil in the static incompressible subsonic regime have been investigated numerically and experimentally. Experimental tests were performed in the incompressible subsonic wind tunnel of the Ghadr National Aerodynamics Research Center of Imam Hossein University with a cross-sectional area of 80 by 100 cm. The simulation of the phenomenon is a fixed ground with the minimum possible thickness of the boundary layer in the wind tunnel. Solve the flow field numerically based on Navier Stokes equations along with the Transition-SST viscous model. The impact of the surface effect phenomenon on the change of aerodynamic coefficients has been investigated by considering different distances from the surface in the static state. The pressure distribution on the airfoil surface is measured by an accurate pressure sensor and is due to the surface effect phenomenon at close distances to the surface. The results of the static analysis show an increase in lift force and a decrease in drag force.

https://mej.aut.ac.ir/article_4476_ab6439fa2daf0246f92eea433bca5ac4.pdf

Amirkabir University of Technology Amirkabir Journal of Mechanical Engineering 2008-6032 54 1 2022 03 21 Numerical Analysis of the Effect of Configurations of Double Rotating Cylinders on Heat Transfer Enhancement Hybrid Nanofluid Flow in a Vented Cavity Numerical Analysis of the Effect of Configurations of Double Rotating Cylinders on Heat Transfer Enhancement Hybrid Nanofluid Flow in a Vented Cavity 145 168 4421 10.22060/mej.2021.19823.7125 FA Hesam Moayedi Thermo-Fluids Department, Faculty of Mechanical Engineering, University of Guilan, Iran 0000-0002-8320-5292 Journal Article 2021 04 06 In this paper, the effect of configurations of rotating cylinders in a vented cavity with inlet and outlet port on the flow field and heat transfer enhancement of forced convection of Al2O3/Cu-water hybrid nanofluid flow in the laminar regime is numerically investigated. In this study, the influence of parameters as configurations of cylinders (A, B, C, and D), as well as the rotational velocity of cylinders (from -10 to +10), Reynolds number (from 100 to 500), and the volume fraction of nanoparticles (from 0.5% to 3%) on the flow field and heat transfer are studied. Results indicate that the average Nusselt number and the Performance Evaluation Index for configuration D are higher than other configurations. Also, it is obvious that by increasing the rotational velocity of cylinders, Reynolds number, and the volume fraction of nanoparticles, the Performance Evaluation Index increases. Also, by rotating the cylinders in the counterclockwise rotation direction with respect to the clockwise rotation direction, the η increases about 1.30. The results show that Al2O3/Cu-water hybrid nanofluid causes heat transfer enhancement compared to the Cu-water nanofluid and it increases the Performance Evaluation Index compared to the Al2O3-water nanofluid. In this paper, the effect of configurations of rotating cylinders in a vented cavity with inlet and outlet port on the flow field and heat transfer enhancement of forced convection of Al2O3/Cu-water hybrid nanofluid flow in the laminar regime is numerically investigated. In this study, the influence of parameters as configurations of cylinders (A, B, C, and D), as well as the rotational velocity of cylinders (from -10 to +10), Reynolds number (from 100 to 500), and the volume fraction of nanoparticles (from 0.5% to 3%) on the flow field and heat transfer are studied. Results indicate that the average Nusselt number and the Performance Evaluation Index for configuration D are higher than other configurations. Also, it is obvious that by increasing the rotational velocity of cylinders, Reynolds number, and the volume fraction of nanoparticles, the Performance Evaluation Index increases. Also, by rotating the cylinders in the counterclockwise rotation direction with respect to the clockwise rotation direction, the η increases about 1.30. The results show that Al2O3/Cu-water hybrid nanofluid causes heat transfer enhancement compared to the Cu-water nanofluid and it increases the Performance Evaluation Index compared to the Al2O3-water nanofluid.

https://mej.aut.ac.ir/article_4421_12ced2db6f0193dda91ba86224ea1cd8.pdf

Amirkabir University of Technology Amirkabir Journal of Mechanical Engineering 2008-6032 54 1 2022 03 21 Numerical Simulation of Convective Heat Transfer of Nano-Encapsulated Phase Change Material Slurries in Micro-Channels with Sinusoidal Cavities and Rectangular Ribs Numerical Simulation of Convective Heat Transfer of Nano-Encapsulated Phase Change Material Slurries in Micro-Channels with Sinusoidal Cavities and Rectangular Ribs 169 188 4432 10.22060/mej.2021.19791.7113 FA Hadi Nemati-Moghadam Department of Mechanical Engineering,, Amirkabir University of Technology, Tehran, Iran. Ali Ahmadpour Department of Mechanical Engineering,, Amirkabir University of Technology, Tehran, Iran. Mohammad Reza Hajmohammadi Department of Mechanical Engineering,, Amirkabir University of Technology, Tehran, Iran. Journal Article 2021 03 25 In the present study, the Thermo-hydraulic performance evaluation of nano-encapsulated phase change material slurries was undertaken in a micro-channel heat sink. The present research was motivated by the urgent need for the performance enhancement of micro-sized heat sinks for the electronic cooling application. A micro-channel with sinusoidal cavities and rectangular ribs was chosen as the flow domain in the present study and the steady laminar flow of nano-encapsulated phase change material slurries was investigated inside the micro-channel. A single-phase model was adopted for the simulation of slurry flow and heat transfer using the well-known finite volume method. Ansys Fluent software was used to solve the governing equations and simulate the flow. In the current study, Nusselt number, friction factor, and performance factor were used to measure the thermal-hydrodynamic performance of the studied slurries. Numerical simulations were performed for Reynolds numbers ranging from 200 to 1000 and nanoparticle concentrations ranging from 0 to 30%. It was shown that adding nano-encapsulated phase change material to a base fluid like water enhanced the thermal performance of the resulting slurry. A 6% to 48% increase in the Nusselt number was reported along the microchannel. In the present study, the Thermo-hydraulic performance evaluation of nano-encapsulated phase change material slurries was undertaken in a micro-channel heat sink. The present research was motivated by the urgent need for the performance enhancement of micro-sized heat sinks for the electronic cooling application. A micro-channel with sinusoidal cavities and rectangular ribs was chosen as the flow domain in the present study and the steady laminar flow of nano-encapsulated phase change material slurries was investigated inside the micro-channel. A single-phase model was adopted for the simulation of slurry flow and heat transfer using the well-known finite volume method. Ansys Fluent software was used to solve the governing equations and simulate the flow. In the current study, Nusselt number, friction factor, and performance factor were used to measure the thermal-hydrodynamic performance of the studied slurries. Numerical simulations were performed for Reynolds numbers ranging from 200 to 1000 and nanoparticle concentrations ranging from 0 to 30%. It was shown that adding nano-encapsulated phase change material to a base fluid like water enhanced the thermal performance of the resulting slurry. A 6% to 48% increase in the Nusselt number was reported along the microchannel.

https://mej.aut.ac.ir/article_4432_da94cbeff56cfda50785df477941308b.pdf

Amirkabir University of Technology Amirkabir Journal of Mechanical Engineering 2008-6032 54 1 2022 03 21 Numerical Study and Sensitivity Analysis in Tubular Heat Exchangers with Perforated Conical Rings Carrying Water-Aluminum Oxide Nanofluid Numerical Study and Sensitivity Analysis in Tubular Heat Exchangers with Perforated Conical Rings Carrying Water-Aluminum Oxide Nanofluid 189 210 4479 10.22060/mej.2021.19808.7120 FA Mohsen Mohammadi university of urmia Seyed Mehdi Pesteei Faculty member of Mechanical Engineering Department of Urmia University Journal Article 2021 03 31 In this paper, the hydrodynamic behavior and heat transfer of a nanofluid turbulent flow in an exchanger equipped with perforated conical rings are simulated numerically. Water-based fluid and Al2O3 nanoparticles with a weight percentage of zero to 5% are considered as nanoparticles that increase heat transfer. The governing equations are solved using the computational fluid dynamics method with the help of ANSYS-Fluent software in the range of Reynolds 12000-2000. After validation of the numerical solution method with the available experimental results, the effect of geometric parameters and flow characteristics such as Reynolds number, number of rings used, number of holes used and volume fraction of nanoparticles on the heat transfer characteristics of the heat exchanger have been studied. The results show that the use of perforated conical rings has a significant effect on improving heat transfer in heat exchangers and this method can be used in practical applications. The results show that with increasing the number of conical rings, decreasing the number of holes, and increasing the weight fraction of nanoparticles, the Nusselt number and the coefficient of friction increase. Based on the results, it can be seen that the proposed loop can increase the Nusselt number by 5.3 times compared to the tube without the loop. In addition, Al2O3 nanoparticles have a favorable effect on increasing heat transfer and with increasing the volume fraction of Al2O3 nanoparticles from zero to 5%, Nusselt number per m = 1 and n = 3 about 92% increase in Nusselt number has been observed. In this paper, the hydrodynamic behavior and heat transfer of a nanofluid turbulent flow in an exchanger equipped with perforated conical rings are simulated numerically. Water-based fluid and Al2O3 nanoparticles with a weight percentage of zero to 5% are considered as nanoparticles that increase heat transfer. The governing equations are solved using the computational fluid dynamics method with the help of ANSYS-Fluent software in the range of Reynolds 12000-2000. After validation of the numerical solution method with the available experimental results, the effect of geometric parameters and flow characteristics such as Reynolds number, number of rings used, number of holes used and volume fraction of nanoparticles on the heat transfer characteristics of the heat exchanger have been studied. The results show that the use of perforated conical rings has a significant effect on improving heat transfer in heat exchangers and this method can be used in practical applications. The results show that with increasing the number of conical rings, decreasing the number of holes, and increasing the weight fraction of nanoparticles, the Nusselt number and the coefficient of friction increase. Based on the results, it can be seen that the proposed loop can increase the Nusselt number by 5.3 times compared to the tube without the loop. In addition, Al2O3 nanoparticles have a favorable effect on increasing heat transfer and with increasing the volume fraction of Al2O3 nanoparticles from zero to 5%, Nusselt number per m = 1 and n = 3 about 92% increase in Nusselt number has been observed.

https://mej.aut.ac.ir/article_4479_c89ca36e4d0430e75ca2390470a59a59.pdf

Amirkabir University of Technology Amirkabir Journal of Mechanical Engineering 2008-6032 54 1 2022 03 21 Energy, Exergy and Thermoeconomic Analysis of the Novel Combined Cycle of Solid Oxide Fuel Cell and Biogas Steam Reforming for Cogeneration Power and Hydrogen Energy, Exergy and Thermoeconomic Analysis of the Novel Combined Cycle of Solid Oxide Fuel Cell and Biogas Steam Reforming for Cogeneration Power and Hydrogen 211 234 4544 10.22060/mej.2021.19189.6987 FA Elahe Soleimani University of Mohaghegh Ardabili Saeed Ghavami Gargari University of Mohaghegh Ardabili Hadi Ghaebi محقق اردبیلی-فنی و مهندسی- مهندسی مکانیک Shahin Basiri University of Mohaghegh Ardabili Journal Article 2020 11 13 In this paper, a new configuration of a solid oxide fuel cell/gas turbine combined cycle system with a biogas reforming cycle is presented for the purpose of coproduction production of power and hydrogen. The heat output from the base system of the solid oxide fuel cell/gas turbine is used to supply the energy required for the reforming reaction and to drive the biogas reforming cycle for hydrogen production. Comprehensive thermodynamic and thermoeconomic modeling has been performed using engineering equation solver software. Also, the parametric study has been analyzed for the effect of different parameters on the net output power, energy and exergy efficiency, exergy destruction rate, and the sum unit cost products of the whole system. The results show that the energy efficiency and exergy efficiency of the proposed combined system have increased the comparison of the solid oxide fuel cell/gas turbine system by 23.31% and 28.19%, respectively. The net output power and hydrogen production rate are obtained at 2726 kW and 0.07453 kg/s, respectively. From the exergy viewpoint, the afterburner causes a considerable amount of exergy destruction for the system by approximately 26% of the total exergy destruction rate. By increasing the inlet temperature fuel cell, the cell voltage reaches a maximum value at a temperature of 679 K and then decreases. As a result, energy and exergy efficiency are maximized and then reduced. Besides, the total exergy destruction rate and sum unit cost product of the cogeneration system is calculated equals to 1532 kW and 9400 $/GJ, respectively. In this paper, a new configuration of a solid oxide fuel cell/gas turbine combined cycle system with a biogas reforming cycle is presented for the purpose of coproduction production of power and hydrogen. The heat output from the base system of the solid oxide fuel cell/gas turbine is used to supply the energy required for the reforming reaction and to drive the biogas reforming cycle for hydrogen production. Comprehensive thermodynamic and thermoeconomic modeling has been performed using engineering equation solver software. Also, the parametric study has been analyzed for the effect of different parameters on the net output power, energy and exergy efficiency, exergy destruction rate, and the sum unit cost products of the whole system. The results show that the energy efficiency and exergy efficiency of the proposed combined system have increased the comparison of the solid oxide fuel cell/gas turbine system by 23.31% and 28.19%, respectively. The net output power and hydrogen production rate are obtained at 2726 kW and 0.07453 kg/s, respectively. From the exergy viewpoint, the afterburner causes a considerable amount of exergy destruction for the system by approximately 26% of the total exergy destruction rate. By increasing the inlet temperature fuel cell, the cell voltage reaches a maximum value at a temperature of 679 K and then decreases. As a result, energy and exergy efficiency are maximized and then reduced. Besides, the total exergy destruction rate and sum unit cost product of the cogeneration system is calculated equals to 1532 kW and 9400 $/GJ, respectively.

https://mej.aut.ac.ir/article_4544_78f1893678afbeaa90b1fa01b9cfb860.pdf

Amirkabir University of Technology Amirkabir Journal of Mechanical Engineering 2008-6032 54 1 2022 03 21 Investigation of The Surface Flame Burner Functional Diagram Using Chemiluminescence and Image Analysis Investigation of The Surface Flame Burner Functional Diagram Using Chemiluminescence and Image Analysis 235 248 4540 10.22060/mej.2021.19602.7063 FA Ziaulhaq Ahmadi Tarbiat Modares Mohammad Zabetian Targhi تربیت مدرس-مهندسی مکانیک Journal Article 2021 02 08 In this study, a fully premixed cylindrical surface flame burner is investigated in laboratory research. The burner was analyzed in heating capacities 11.74-17.14 kW and its equivalence ratio 0.4-1.6. The results are including two sections of spectroscopy and flame image analysis. In the chemiluminescence section, the maximum heat release from the perforated cylindrical burner is obtained by examining the intensity of hydroxyl radiation in the equivalence ratio of 0.8. In the second part of chemiluminescence, the equivalence ratio is estimated by using the intensity ratio and curve fitting from natural flame radiation. The color and state of the flame changed from the equivalence ratio of 1.6 to 0.44, respectively, from green to yellow and red flame, blue and lift-off flame, and eventually blow-off. The satisfactory operation that is stable blue flame without lift-off and flashback is observed in the range of 0.7-0.85. This process was performed for six thermal capacities, and its results were collected in a chart called the functional burner diagram. A satisfactory operation can be selected by a functional diagram in different burner powers. In this study, a fully premixed cylindrical surface flame burner is investigated in laboratory research. The burner was analyzed in heating capacities 11.74-17.14 kW and its equivalence ratio 0.4-1.6. The results are including two sections of spectroscopy and flame image analysis. In the chemiluminescence section, the maximum heat release from the perforated cylindrical burner is obtained by examining the intensity of hydroxyl radiation in the equivalence ratio of 0.8. In the second part of chemiluminescence, the equivalence ratio is estimated by using the intensity ratio and curve fitting from natural flame radiation. The color and state of the flame changed from the equivalence ratio of 1.6 to 0.44, respectively, from green to yellow and red flame, blue and lift-off flame, and eventually blow-off. The satisfactory operation that is stable blue flame without lift-off and flashback is observed in the range of 0.7-0.85. This process was performed for six thermal capacities, and its results were collected in a chart called the functional burner diagram. A satisfactory operation can be selected by a functional diagram in different burner powers.

https://mej.aut.ac.ir/article_4540_0f65caf0a7d00afd2b87c028e88fe931.pdf

Amirkabir University of Technology Amirkabir Journal of Mechanical Engineering 2008-6032 54 1 2022 03 21 Study of The Effect of Wall Temperature and Oxidant Structure on Temperature Distribution and NO Emission in Non-Premixed Combustion Furnace Study of The Effect of Wall Temperature and Oxidant Structure on Temperature Distribution and NO Emission in Non-Premixed Combustion Furnace 249 266 4504 10.22060/mej.2021.19792.7114 FA Amin Tajdani PhD Student of Kashan University, Kashan, Iran Seyed Abdolmehdi Hashemi 0000-0001-7169-7173 Esmaeil Ebrahimi Fordoei Faculty of Mechanical Engineering , Tarbiat Modares University Journal Article 2021 03 26 The aim of this study was to investigate the effect of the thermal condition of furnace wall and oxidant structure on NOx emission and thermal conditions inside the non-premixed combustion furnace. For this purpose, non-premixed combustion furnace simulations have been performed using OpenFOAM software. Standard k-ε turbulence model, modified eddy dissipation concept combustion model, and discrete ordinates radiation model are used in numerical simulations. In order to analyze the results of numerical simulations, chemical calculations using a well stirred reactor have also been considered. According to the results, increasing the furnace wall temperature to reach thermal insulation conditions leads to a significant increase in the average and maximum temperature inside the combustion chamber and transfers the combustion regime from flameless to high temperature. In addition, the replacement of carbon dioxide with nitrogen will be accompanied by a decrease in the combustion temperature due to physical and chemical differences between the two species. According to the results, increasing the wall temperature, despite reducing the heat loss, leads to an increase in NOx in the high temperature combustion regime. The use of carbon dioxide instead of nitrogen in an oxidizer can be considered as a way to reduce heat loss while reducing NOx emission from the non-premixed combustion furnace. The aim of this study was to investigate the effect of the thermal condition of furnace wall and oxidant structure on NOx emission and thermal conditions inside the non-premixed combustion furnace. For this purpose, non-premixed combustion furnace simulations have been performed using OpenFOAM software. Standard k-ε turbulence model, modified eddy dissipation concept combustion model, and discrete ordinates radiation model are used in numerical simulations. In order to analyze the results of numerical simulations, chemical calculations using a well stirred reactor have also been considered. According to the results, increasing the furnace wall temperature to reach thermal insulation conditions leads to a significant increase in the average and maximum temperature inside the combustion chamber and transfers the combustion regime from flameless to high temperature. In addition, the replacement of carbon dioxide with nitrogen will be accompanied by a decrease in the combustion temperature due to physical and chemical differences between the two species. According to the results, increasing the wall temperature, despite reducing the heat loss, leads to an increase in NOx in the high temperature combustion regime. The use of carbon dioxide instead of nitrogen in an oxidizer can be considered as a way to reduce heat loss while reducing NOx emission from the non-premixed combustion furnace.

https://mej.aut.ac.ir/article_4504_124461dcd3571e6674ec4e0e140cc298.pdf