Amirkabir University of TechnologyAmirkabir Journal of Mechanical Engineering2008-603254920221122Numerical Simulation of an Electro-Cyclone for Classification of Micron-Sized ParticlesNumerical Simulation of an Electro-Cyclone for Classification of Micron-Sized Particles19711988491810.22060/mej.2022.20926.7341FAArminDarabiDepartment of Mechanical Engineering, Imam Khomeini International University, Qazvin, Iran.AliMomenimovahedDepartment of Mechanical Engineering, Imam Khomeini International University, Qazvin, Iran.Journal Article20211230Cyclones are normally used to separate relatively larger particles from the aerosol. In this article, the feasibility of using a cyclone to classify particles in a specific mass range by applying an electric field between the outer cylinder and the vortex finder is studied. Moreover, the effect of cyclone geometry and electric field intensity on the cyclone efficiency and the classified particle diameter is quantified. The finite element method was used for the simulations of 3D, steady, and two-phase flow. It should be noted that the Reynolds number of inlet flow ranged between 4,000 to10,000. The results reveal that the diameters of the inner and outer cylinders have negligible effects on cyclone efficiency. However, an increase in the length of the cyclone specifically the length of the vortex finder can significantly affect the cyclone performance which can be attributed to the higher particle residence time within the cyclone. For cyclones with twice larger cylinders, the classification efficiency is 6% to17% higher based on the geometric standard deviation of the particle size distribution. It was also shown that different particle masses can be classified by adjusting the flow rate of the inlet aerosol or the magnitude of the electric field applied to the charged particles.Cyclones are normally used to separate relatively larger particles from the aerosol. In this article, the feasibility of using a cyclone to classify particles in a specific mass range by applying an electric field between the outer cylinder and the vortex finder is studied. Moreover, the effect of cyclone geometry and electric field intensity on the cyclone efficiency and the classified particle diameter is quantified. The finite element method was used for the simulations of 3D, steady, and two-phase flow. It should be noted that the Reynolds number of inlet flow ranged between 4,000 to10,000. The results reveal that the diameters of the inner and outer cylinders have negligible effects on cyclone efficiency. However, an increase in the length of the cyclone specifically the length of the vortex finder can significantly affect the cyclone performance which can be attributed to the higher particle residence time within the cyclone. For cyclones with twice larger cylinders, the classification efficiency is 6% to17% higher based on the geometric standard deviation of the particle size distribution. It was also shown that different particle masses can be classified by adjusting the flow rate of the inlet aerosol or the magnitude of the electric field applied to the charged particles.https://mej.aut.ac.ir/article_4918_62f1dbd6079772fadd0bc58514bdc37c.pdfAmirkabir University of TechnologyAmirkabir Journal of Mechanical Engineering2008-603254920221122Investigation of Different Internal Flows Using Different Transitional ModelsInvestigation of Different Internal Flows Using Different Transitional Models19892008490610.22060/mej.2022.20999.7361FAMohammadaliModaresiDepartment of Mechanical Engineering, Tarbiat Modares University, Tehran, IranAmirYousefiDepartment of Mechanical Engineering, Tarbiat Modares University, Tehran, IranGhassemHeidarinejadDepartment of Mechanical Engineering, Tarbiat Modares University, Tehran, IranJournal Article20220121<span style="letter-spacing: .05pt;">Prediction of flow behavior in the transition region is the key issue in many scientific problems. Many attempts have been made by researchers to propose and modify the models estimating the flow behavior in this region. In these flows, the governing equations, including the continuity, the Navier-Stokes, and the transmittance along with the Shear Stress Transport models are solved simultaneously to predict the flow behavior. There are several coefficients in the governing equations which affect the flow simulation. In this study, the transitional shear stress transport model is modified by altering two coefficients in the intermittency equation. A combination of these coefficients is implemented, and the effects are studied. To assess the accuracy of the proposed coefficients in simulation, they are applied to three individual internal flows, including a smooth axisymmetric pipe, two parallel plates, and a backward-facing step. Different variables such as the friction factor coefficient, fully developed friction factor, and the reattachment length are explored. A comparison between the results and both analytical and experimental data confirms a good accuracy in the predictions. Furthermore, using the presented models the entrance length is well predicted in turbulent and transitional flows.</span><span style="letter-spacing: .05pt;">Prediction of flow behavior in the transition region is the key issue in many scientific problems. Many attempts have been made by researchers to propose and modify the models estimating the flow behavior in this region. In these flows, the governing equations, including the continuity, the Navier-Stokes, and the transmittance along with the Shear Stress Transport models are solved simultaneously to predict the flow behavior. There are several coefficients in the governing equations which affect the flow simulation. In this study, the transitional shear stress transport model is modified by altering two coefficients in the intermittency equation. A combination of these coefficients is implemented, and the effects are studied. To assess the accuracy of the proposed coefficients in simulation, they are applied to three individual internal flows, including a smooth axisymmetric pipe, two parallel plates, and a backward-facing step. Different variables such as the friction factor coefficient, fully developed friction factor, and the reattachment length are explored. A comparison between the results and both analytical and experimental data confirms a good accuracy in the predictions. Furthermore, using the presented models the entrance length is well predicted in turbulent and transitional flows.</span>https://mej.aut.ac.ir/article_4906_75b5913f006a37d172314ab07a879455.pdfAmirkabir University of TechnologyAmirkabir Journal of Mechanical Engineering2008-603254920221122Numerical Simulation of Induced Vibrations Due to Low Frequency Flow Oscillations around Piezoelectric Blades to Design the Best Configuration for Energy HarvestingNumerical Simulation of Induced Vibrations Due to Low Frequency Flow Oscillations around Piezoelectric Blades to Design the Best Configuration for Energy Harvesting20092040480810.22060/mej.2022.21049.7367FAMehranHeidariCFD, Turbulence and Combustion Research Lab., Department of Mechanical Engineering, University of Qom, Qom, IranMohammad KazemMoayyediCFD, Turbulence and Combustion Research Lab., Department of Mechanical Engineering, University of Qom, Qom, Iran0000-0003-4016-1557Journal Article20220130One of the most important issues facing today's society is the issue of energy production and the challenges surrounding it. For this reason, it is very important to address the issue of energy harvesting from various methods. One of these methods is energy harvesting from vibrations caused by fluid flow. Vibrations generated by the incompressible air fluid flow around three parallel piezoelectric blades behind a circular cylinder at different longitudinal distances can be one of the best options for examining and evaluating the amount of electrical voltage generated by piezoelectric blade vibrations. According to this study, a situation in which the middle piezoelectric blade is shifted by half the length of the blade to the right and the direction of the clamp is opposite to the direction of the clamp of the up and down blades is the optimal structure for voltage output and reducing collision probability. Due to the reduced probability of the blades colliding with each other in this optimal case, the maximum Reynolds number without the blades colliding increased from 2400 in non-optimal structures to 2600 in the optimal structure, which increased the voltage output in the middle blade by 12% and about 14% for up and down blades.One of the most important issues facing today's society is the issue of energy production and the challenges surrounding it. For this reason, it is very important to address the issue of energy harvesting from various methods. One of these methods is energy harvesting from vibrations caused by fluid flow. Vibrations generated by the incompressible air fluid flow around three parallel piezoelectric blades behind a circular cylinder at different longitudinal distances can be one of the best options for examining and evaluating the amount of electrical voltage generated by piezoelectric blade vibrations. According to this study, a situation in which the middle piezoelectric blade is shifted by half the length of the blade to the right and the direction of the clamp is opposite to the direction of the clamp of the up and down blades is the optimal structure for voltage output and reducing collision probability. Due to the reduced probability of the blades colliding with each other in this optimal case, the maximum Reynolds number without the blades colliding increased from 2400 in non-optimal structures to 2600 in the optimal structure, which increased the voltage output in the middle blade by 12% and about 14% for up and down blades.https://mej.aut.ac.ir/article_4808_88f33ce2eee4a700c02c5d5cdf482514.pdfAmirkabir University of TechnologyAmirkabir Journal of Mechanical Engineering2008-603254920221122The Interaction of the Shock Wave with the Bubble and the Effect of Computational Grid Size on the Problem Simulation with A Fully Coupled Pressure-Based AlgorithmThe Interaction of the Shock Wave with the Bubble and the Effect of Computational Grid Size on the Problem Simulation with A Fully Coupled Pressure-Based Algorithm20412060486710.22060/mej.2022.21189.7395FAMohammadPiraniEnergy Conversion / Faculty of Mechanical Engineering / Tarbiat Modares University / Tehran / Iran0000-0002-7994-1000AriyaRahmanitarbia modares universityMohammad RezaAnsaritarbiat modares universityJournal Article20220306<span style="letter-spacing: .05pt;">When a shock wave propagates through a flow field that has nonlinear thermodynamic properties, different processes occur simultaneously. Wave compression, wave refraction, and vortex generation are examples of these processes that cause the waveform and thermodynamic properties of the fluid to change. The interaction of a shock wave with a cylindrical bubble is an example of a wave-bubble collision problem in which all of the above processes are observed. Due to the high computational cost of density-based algorithms in solving compressible interfacial flow problems such as shock wave interaction with the two-phase flow, using a fully coupled pressure-based algorithm is a good solution that will solve the problem with proper accuracy while reducing computation time. In this paper, using this algorithm, the interaction of the shock wave with the bubble is investigated; while validating the results, the effect of the computational grid size and the method of discretization of the governing equations are determined. It was observed that by increasing the number of computational grids according to the first-order upwind method, the simulation results become more accurate, and the numerical diffusion amount decreases. Also, by changing the discretization method to second-order upwind, the instabilities on the interface of the two phases increase due to spurious fluctuations, and the shape of the interface obtained from the numerical solution moves away from the experimental results.</span><span style="letter-spacing: .05pt;">When a shock wave propagates through a flow field that has nonlinear thermodynamic properties, different processes occur simultaneously. Wave compression, wave refraction, and vortex generation are examples of these processes that cause the waveform and thermodynamic properties of the fluid to change. The interaction of a shock wave with a cylindrical bubble is an example of a wave-bubble collision problem in which all of the above processes are observed. Due to the high computational cost of density-based algorithms in solving compressible interfacial flow problems such as shock wave interaction with the two-phase flow, using a fully coupled pressure-based algorithm is a good solution that will solve the problem with proper accuracy while reducing computation time. In this paper, using this algorithm, the interaction of the shock wave with the bubble is investigated; while validating the results, the effect of the computational grid size and the method of discretization of the governing equations are determined. It was observed that by increasing the number of computational grids according to the first-order upwind method, the simulation results become more accurate, and the numerical diffusion amount decreases. Also, by changing the discretization method to second-order upwind, the instabilities on the interface of the two phases increase due to spurious fluctuations, and the shape of the interface obtained from the numerical solution moves away from the experimental results.</span>https://mej.aut.ac.ir/article_4867_8cd61bd5d9d4a0e08673c0514cfa29b0.pdfAmirkabir University of TechnologyAmirkabir Journal of Mechanical Engineering2008-603254920221122Numerical Simulation of Aero-Acoustic Noise from Supersonic Jet Reflection Using Computational Fluid Dynamics/Boundary Element MethodNumerical Simulation of Aero-Acoustic Noise from Supersonic Jet Reflection Using Computational Fluid Dynamics/Boundary Element Method20612084494310.22060/mej.2022.21230.7406FAMaryamBabaei DookiMSc, Aerospace Engineering, Malek Ashtar University of Technologyو ،ثاقشدو ]قشدHamidParhizkarSajjadGhasemlooyAssistant Professor, Faculty of Aerospace Engineering, Malek Ashtar University of Technology, Tehran, IranJournal Article20220317Calculating acoustic loads due to the flow field produced by the outlet flow of launch vehicles impinging on the launch pad is one of the main challenges in the space industry. The sound level of outlet flow from the engine and reflection of produced acoustic waves from the launch pad and their effect on payloads depends on the turbulence parameters, created vortices, nozzle geometry, and launch pad geometry. The present paper aims to calculate the sound level generated by supersonic flow at the outlet of the launch vehicle engine besides the sound reflection from the flow deflector below the engine using a hybrid computational fluid dynamics/ boundary element method. For this purpose, the sound produced by the nozzle outlet flow in the supersonic engine of a launch vehicle is studied. In order to observe the effect of the reflection of acoustic waves from the launch pad, results are compared between two cases (with a flow deflector and without it). Numerical simulation is performed for the three-dimensional viscous compressible turbulent flow, and the boundary element method is used to compute the propagation and reflection of acoustic waves. Obtained results indicate that the generated noise level impressively increases when considering acoustic wave reflection from the deflector. The noise level generated by the projectile engine in the presence of a jet flow deflector is higher by about 8-10 dB than in the absence of a deflector. Also, results show that the acoustic waves over the projectile become more uniform by using a deflector.Calculating acoustic loads due to the flow field produced by the outlet flow of launch vehicles impinging on the launch pad is one of the main challenges in the space industry. The sound level of outlet flow from the engine and reflection of produced acoustic waves from the launch pad and their effect on payloads depends on the turbulence parameters, created vortices, nozzle geometry, and launch pad geometry. The present paper aims to calculate the sound level generated by supersonic flow at the outlet of the launch vehicle engine besides the sound reflection from the flow deflector below the engine using a hybrid computational fluid dynamics/ boundary element method. For this purpose, the sound produced by the nozzle outlet flow in the supersonic engine of a launch vehicle is studied. In order to observe the effect of the reflection of acoustic waves from the launch pad, results are compared between two cases (with a flow deflector and without it). Numerical simulation is performed for the three-dimensional viscous compressible turbulent flow, and the boundary element method is used to compute the propagation and reflection of acoustic waves. Obtained results indicate that the generated noise level impressively increases when considering acoustic wave reflection from the deflector. The noise level generated by the projectile engine in the presence of a jet flow deflector is higher by about 8-10 dB than in the absence of a deflector. Also, results show that the acoustic waves over the projectile become more uniform by using a deflector.https://mej.aut.ac.ir/article_4943_8514f8481aae3dffb81d01d82ccfa893.pdfAmirkabir University of TechnologyAmirkabir Journal of Mechanical Engineering2008-603254920221122Numerical Modeling of Li-Ion Battery Temperature Control System at Low Initial TemperatureNumerical Modeling of Li-Ion Battery Temperature Control System at Low Initial Temperature20852102495110.22060/mej.2022.20343.7212FAPedramShamsizadehDepartment of Mechanical Engineering, Faculty of Engineering, University of Isfahan, Isfahan, IranEbrahimAfshariJournal Article20210729Li-ion battery temperature affects its performance, significantly, and keeping its temperature in proper operational temperature is obligatory; so, this guarantees the performance, safety, and life span of the battery. In this study, the performance of the planar Li-ion battery temperature management system with 6 cells in cold weather (initial temperature -20<sup>o</sup>C) is investigated. The maximum temperature difference and the average temperature of the battery cells are the two main performance criteria of the temperature management system. Effects of mass flow rate, number of heating plates, and flow arrangement consisting of parallel, counter, and zig-zag flow arrangements on the performance criterion and also on the warm-up time are studied. Results show that by increasing the fluid mass flow rate batteries reach the proper temperature (20<sup> o</sup>C) faster and the temperature difference decreases. At a constant mass rate, the addition of heating plates decreases the warm-up time. The zig-zag flow arrangement has better performance in terms of temperature difference criteria up to 8 times and reaches 2.1 degrees at the maximum value, but parallel-flow warms up the batteries faster than the other flow arrangements.Li-ion battery temperature affects its performance, significantly, and keeping its temperature in proper operational temperature is obligatory; so, this guarantees the performance, safety, and life span of the battery. In this study, the performance of the planar Li-ion battery temperature management system with 6 cells in cold weather (initial temperature -20<sup>o</sup>C) is investigated. The maximum temperature difference and the average temperature of the battery cells are the two main performance criteria of the temperature management system. Effects of mass flow rate, number of heating plates, and flow arrangement consisting of parallel, counter, and zig-zag flow arrangements on the performance criterion and also on the warm-up time are studied. Results show that by increasing the fluid mass flow rate batteries reach the proper temperature (20<sup> o</sup>C) faster and the temperature difference decreases. At a constant mass rate, the addition of heating plates decreases the warm-up time. The zig-zag flow arrangement has better performance in terms of temperature difference criteria up to 8 times and reaches 2.1 degrees at the maximum value, but parallel-flow warms up the batteries faster than the other flow arrangements.https://mej.aut.ac.ir/article_4951_9c5e1b1e61d9cf73af9435840647a98d.pdfAmirkabir University of TechnologyAmirkabir Journal of Mechanical Engineering2008-603254920221122Experimental Study of the Effect of Distilled Water-Conducting Threads on the Performance of Stepped Solar StillExperimental Study of the Effect of Distilled Water-Conducting Threads on the Performance of Stepped Solar Still21032120496210.22060/mej.2022.21132.7382FAMohammadKhaliliDepartment of Mechanical Engineering, Faculty of Engineering, Arak University, Arak, Iran0000-0002-2591-8366MoeinTaheriDepartment of Mechanical Engineering, Faculty of Engineering, Arak University, Arak, Iran0000-0001-6583-3925MiladSalehiDepartment of Mechanical Engineering, Faculty of Engineering, Arak University, Arak, IranZahra SadatEghdamiDepartment of Mechanical Engineering, Faculty of Engineering, Arak University, Arak, IranJournal Article20220221Academics are interested in solar energy for water purification because it is easily accessible. In this investigation, a stepped solar still was constructed and tested experimentally in Arak. Using the Taguchi design of experiment approach, it was determined how the five input parameters-saline water flow rate, device angle, absorber plate color, number, and spacing of distilled water-conducting threads in each row-affected the amount of freshwater production as the output variable. This research is unique in that it uses plastic threads to create channels on the cover glass surface that lead distilled water to the freshwater tank. In addition, the simultaneous study of the effect of input parameters is one of the innovations of this research. The results showed that when the input saline water flow rate was 50 ml/min, the device angle was 40°, the absorber plate was black, the number of water-conducting threads in each row was 2, and the row spacing was 8 mm, the greatest freshwater output of 1975 ml/m<sup>2</sup> was produced. Also, by using two water-conducting threads in each row and spacing them 8 mm apart, the amount of water produced per unit of surface area was increased.Academics are interested in solar energy for water purification because it is easily accessible. In this investigation, a stepped solar still was constructed and tested experimentally in Arak. Using the Taguchi design of experiment approach, it was determined how the five input parameters-saline water flow rate, device angle, absorber plate color, number, and spacing of distilled water-conducting threads in each row-affected the amount of freshwater production as the output variable. This research is unique in that it uses plastic threads to create channels on the cover glass surface that lead distilled water to the freshwater tank. In addition, the simultaneous study of the effect of input parameters is one of the innovations of this research. The results showed that when the input saline water flow rate was 50 ml/min, the device angle was 40°, the absorber plate was black, the number of water-conducting threads in each row was 2, and the row spacing was 8 mm, the greatest freshwater output of 1975 ml/m<sup>2</sup> was produced. Also, by using two water-conducting threads in each row and spacing them 8 mm apart, the amount of water produced per unit of surface area was increased.https://mej.aut.ac.ir/article_4962_9b889646238e43c84f7800cd36b375e5.pdfAmirkabir University of TechnologyAmirkabir Journal of Mechanical Engineering2008-603254920221122Synthesis of Carbonous Nano Adsorbents and Their Application in Methane Gas StorageSynthesis of Carbonous Nano Adsorbents and Their Application in Methane Gas Storage21212138497210.22060/mej.2022.21145.7387FAMehdiHasan SoltaniFaculty of Chemical Engineering, Urmia University of Technology, Urmia, IranSeyed SalarMeshkatFaculty of Chemical Engineering, Urmia University of Technology, Urmia, IranArashAfghanFaculty of Chemical Engineering, Urmia University of Technology, Urmia, IranJournal Article20220225In this research, adsorbed natural gas methods have been studied. The adsorbents used in this thesis are carbon-based nano-sorbents (activated carbon, pure and functionalized carbon nanotubes, and porous graphene) which were synthesized by the chemical vapor deposition method. The accuracy of synthesized results was examined using scanning electron microscopy, transmission electron microscopy, Fourier-transform infrared spectroscopy, X-ray diffraction, and Brunauer–Emmett–Teller analyses. The adsorption capacity of adsorbents for methane gas adsorption at three temperatures of 28, 45, and 60 ° C was calculated and matched with three isotherm equations of Langmuir, Freundlich, and Temkin. The <em>R</em> of the Langmuir isotherm for pure and functional nanotube adsorbents were 0.9963 and 0.9997, respectively, and for activated carbon was 0.9995, which is the closest isothermal equation for these adsorbents, while for the graphene adsorbent the closest prediction is Temkin isotherm with calculated <em>R</em> of 0.9986. It can be concluded that with increasing temperature, the amount of adsorbed gas decreases, and with increasing pressure, the amount of adsorbed gas increases. Therefore, the maximum adsorption for all adsorbents occurred at a temperature of 28°C and a pressure of 40 bar. Among the used adsorbents, porous graphene showed the best performance at a temperature of 28°C, and a pressure of 40 bar, which according to its high specific surface area, Brunauer–Emmett–Teller analysis (1200 m<sup>2</sup>/g), and significant pore size, such an outcome was predictable.In this research, adsorbed natural gas methods have been studied. The adsorbents used in this thesis are carbon-based nano-sorbents (activated carbon, pure and functionalized carbon nanotubes, and porous graphene) which were synthesized by the chemical vapor deposition method. The accuracy of synthesized results was examined using scanning electron microscopy, transmission electron microscopy, Fourier-transform infrared spectroscopy, X-ray diffraction, and Brunauer–Emmett–Teller analyses. The adsorption capacity of adsorbents for methane gas adsorption at three temperatures of 28, 45, and 60 ° C was calculated and matched with three isotherm equations of Langmuir, Freundlich, and Temkin. The <em>R</em> of the Langmuir isotherm for pure and functional nanotube adsorbents were 0.9963 and 0.9997, respectively, and for activated carbon was 0.9995, which is the closest isothermal equation for these adsorbents, while for the graphene adsorbent the closest prediction is Temkin isotherm with calculated <em>R</em> of 0.9986. It can be concluded that with increasing temperature, the amount of adsorbed gas decreases, and with increasing pressure, the amount of adsorbed gas increases. Therefore, the maximum adsorption for all adsorbents occurred at a temperature of 28°C and a pressure of 40 bar. Among the used adsorbents, porous graphene showed the best performance at a temperature of 28°C, and a pressure of 40 bar, which according to its high specific surface area, Brunauer–Emmett–Teller analysis (1200 m<sup>2</sup>/g), and significant pore size, such an outcome was predictable.https://mej.aut.ac.ir/article_4972_45719ccdcf8900639012cfba6744c03e.pdfAmirkabir University of TechnologyAmirkabir Journal of Mechanical Engineering2008-603254920221122Effect of Obstacles Location and Flow Injection on the Mixing of Two-Gaseous Flow in a MicrochannelEffect of Obstacles Location and Flow Injection on the Mixing of Two-Gaseous Flow in a Microchannel21392156488610.22060/mej.2022.21339.7431FAElyasLekzianFaculty of Aerospace Engineering,, Semnan University, Semnan, IranHamid RezaFarshi FasihFaculty of Aerospace EngineeringJournal Article20220423<span style="letter-spacing: .05pt;">In the present study, the direct simulation Monte Carlo method is utilized to investigate the effect of obstacles number, location, and also flow injection on the mixing in a channel with 16 μm length and 1 μm height. A mixing length is defined which is the length at which two species are mixed completely. Eight cases with different blockage ratios are considered to study the obstacle effect on the mixing. The blockage ratio shows the reduced flow cross-section due to the addition of obstacles. In All cases, CO<sub>2</sub> and N<sub>2</sub> gases enter the domain and are separated by a splitter plate that extends up to 1/3 of the channel. The blockage ratio increasing decreases mixing length by up to 10%. Whereas the mass flow rate decreased significantly. Flow injection into the channel is also studied. Four cases are considered: the first case is a simple channel without injection, the second case has cross injection, the third case has inverse injection, and flow is injected vertically through an obstacle in the fourth case. Mixing length is increased by 17% and 5% for cases 2 and 3, respectively. In case 4, the mixing length is decreased by 2% due to the obstacle.</span><span style="letter-spacing: .05pt;">In the present study, the direct simulation Monte Carlo method is utilized to investigate the effect of obstacles number, location, and also flow injection on the mixing in a channel with 16 μm length and 1 μm height. A mixing length is defined which is the length at which two species are mixed completely. Eight cases with different blockage ratios are considered to study the obstacle effect on the mixing. The blockage ratio shows the reduced flow cross-section due to the addition of obstacles. In All cases, CO<sub>2</sub> and N<sub>2</sub> gases enter the domain and are separated by a splitter plate that extends up to 1/3 of the channel. The blockage ratio increasing decreases mixing length by up to 10%. Whereas the mass flow rate decreased significantly. Flow injection into the channel is also studied. Four cases are considered: the first case is a simple channel without injection, the second case has cross injection, the third case has inverse injection, and flow is injected vertically through an obstacle in the fourth case. Mixing length is increased by 17% and 5% for cases 2 and 3, respectively. In case 4, the mixing length is decreased by 2% due to the obstacle.</span>https://mej.aut.ac.ir/article_4886_9484acce8a92ba052bbb47fad969d6af.pdfAmirkabir University of TechnologyAmirkabir Journal of Mechanical Engineering2008-603254920221122Evaluating the fast method based on proper orthogonal decomposition for radiative heat transfer in a participating mediumEvaluating the fast method based on proper orthogonal decomposition for radiative heat transfer in a participating medium21752174493110.22060/mej.2022.21069.7377FAMohsenNiknam SharakDepartment of Mechanical Engineering, Faculty of Engineering, University of Birjand, Birjand, Iran0000-0002-3114-6278AliSafavinejadDepartment of Mechanical Engineering, Faculty of Engineering, University of Birjand, Birjand, Iran0000-0002-3114-6278Mohammad KazemMoayyediDepartment of Mechanical Engineering, Faculty of Engineering, University of Qom, Qom, Iran0000-0003-4016-1557Journal Article20220212<span style="letter-spacing: .05pt;">The radiative transfer equation models the thermal radiation in a participating medium. Except in specified cases, there is no analytical solution for this equation. Solving the radiative transfer equation with numerical methods is usually time-consuming. This work presents a fast method based on proper orthogonal decomposition to solve the radiative transfer equation. Some variables are selected as independent parameters. The radiative transfer equation for the specified value of these parameters is solved using the discrete ordinates method, and the system responses form the snapshot matrix. The matrix is decomposed singular value decomposition as a product of three matrices. Due to the magnitude of singular values, only a few first columns of these matrices are selected. As a result, the degrees of freedom of the original system are decreased, and a reduced-order model is created. Employing the radial basis functions, the system response, corresponding to any arbitrary input vector (independent parameters), can be approximated with high speed. The results show that the </span>reduced-order method <span style="letter-spacing: .05pt;">has high accuracy compared to the numerical solution. The complexities of the system do not affect the </span>reduced-order method<span style="letter-spacing: .05pt;">. Regardless of the characteristics of the medium (the value of independent parameters), the solution time is the order of 0.02 seconds.</span><span style="letter-spacing: .05pt;">The radiative transfer equation models the thermal radiation in a participating medium. Except in specified cases, there is no analytical solution for this equation. Solving the radiative transfer equation with numerical methods is usually time-consuming. This work presents a fast method based on proper orthogonal decomposition to solve the radiative transfer equation. Some variables are selected as independent parameters. The radiative transfer equation for the specified value of these parameters is solved using the discrete ordinates method, and the system responses form the snapshot matrix. The matrix is decomposed singular value decomposition as a product of three matrices. Due to the magnitude of singular values, only a few first columns of these matrices are selected. As a result, the degrees of freedom of the original system are decreased, and a reduced-order model is created. Employing the radial basis functions, the system response, corresponding to any arbitrary input vector (independent parameters), can be approximated with high speed. The results show that the </span>reduced-order method <span style="letter-spacing: .05pt;">has high accuracy compared to the numerical solution. The complexities of the system do not affect the </span>reduced-order method<span style="letter-spacing: .05pt;">. Regardless of the characteristics of the medium (the value of independent parameters), the solution time is the order of 0.02 seconds.</span>https://mej.aut.ac.ir/article_4931_bb2ec31610f3594dd34cd832f38024e9.pdfAmirkabir University of TechnologyAmirkabir Journal of Mechanical Engineering2008-603254920221122Numerical Investigation of Heat Transfer of Water/Nano-Encapsulated Phase Change Materials in a Cavity Including a Rotating CylinderNumerical Investigation of Heat Transfer of Water/Nano-Encapsulated Phase Change Materials in a Cavity Including a Rotating Cylinder21752194486610.22060/mej.2022.21222.7405FAFarrokhMobadersaniصنعتی ارومیه-مهندسی مکانیکNeginRashidiصنعتی ارومیه-مهندسی مکانیکJournal Article20220315In the present paper, heat transfer in a cavity containing a mixture of water + phase change materials surrounded by nanoparticles is investigated. The left and right walls are fixed at hot and cold temperatures, respectively, and horizontal walls are assumed to be adiabatic. There is a circular rotating cylinder in the center of the hole that can rotate clockwise or counterclockwise. The problem is considered two dimensional and fundamental governing equations such as continuity, momentum, and energy are solved in a coupled manner utilizing the finite element method (FEM). To check the accuracy of the numerical results, a comparison with the outputs of others is provided, which indicates a very good agreement of the results. The parameters studied in this study are: dimensionless radius of the cylinder (R), Rayleigh number (Ra), dimensionless melting temperature of the phase change material (θfu), Stephan number (St) and dimensionless angular velocity of the rotating cylinder (Ω). By increasing the dimensionless radius of the cylinder from R = 0.1 to R = 0.4 Ω = -300, the heat transfer rate enhances by 23.37%. On the other hand, with R = 0.4 and considering no-rotation case, the heat transfer rate will decrease by about 59.7% compared to the cavity without the cylinder. Which indicates the importance of rotation of the cylinder inside the cavity in the heat transfer rate enhancement.In the present paper, heat transfer in a cavity containing a mixture of water + phase change materials surrounded by nanoparticles is investigated. The left and right walls are fixed at hot and cold temperatures, respectively, and horizontal walls are assumed to be adiabatic. There is a circular rotating cylinder in the center of the hole that can rotate clockwise or counterclockwise. The problem is considered two dimensional and fundamental governing equations such as continuity, momentum, and energy are solved in a coupled manner utilizing the finite element method (FEM). To check the accuracy of the numerical results, a comparison with the outputs of others is provided, which indicates a very good agreement of the results. The parameters studied in this study are: dimensionless radius of the cylinder (R), Rayleigh number (Ra), dimensionless melting temperature of the phase change material (θfu), Stephan number (St) and dimensionless angular velocity of the rotating cylinder (Ω). By increasing the dimensionless radius of the cylinder from R = 0.1 to R = 0.4 Ω = -300, the heat transfer rate enhances by 23.37%. On the other hand, with R = 0.4 and considering no-rotation case, the heat transfer rate will decrease by about 59.7% compared to the cavity without the cylinder. Which indicates the importance of rotation of the cylinder inside the cavity in the heat transfer rate enhancement.https://mej.aut.ac.ir/article_4866_0ebcc33d84f2b85a03708e8aca469918.pdfAmirkabir University of TechnologyAmirkabir Journal of Mechanical Engineering2008-603254920221122Numerical Investigation of Channel Cross-section Effect on the Performance of Integrated Thermoelectric Power GeneratorNumerical Investigation of Channel Cross-section Effect on the Performance of Integrated Thermoelectric Power Generator21952212493610.22060/mej.2022.21327.7426FAVahidMofidianM.Sc. Graduate, Faculty of Mechanical Engineering, University of Guilan, Rasht, IranMohammadKaltehDepartment of Mechanical Engineering, University of Guilan0000-0003-3965-3749MasoudHamiPh.D. Student, Faculty of Mechanical Engineering, University of Guilan, Rasht, IranJournal Article20220421Thermoelectric generators are a sustainable and environmentally friendly technology that can recover wasted heat energy and convert it to electricity. Meanwhile, integrated thermoelectric generators have been able to significantly increase the performance of thermoelectric generators. In this paper, the effect of flow channel cross-sections on integrated thermoelectric power generator performance is investigated numerically using the finite volume method. In this regard, various flow channel configurations including circles, trapezoids, squares, and rectangles have been taken into account and the effect of cross-sectional area ratio, semiconductor length, and Reynolds number on the performance of the device has been evaluated. In this study, the top and bottom of conductor surfaces are exposed to a cold temperature and a hot fluid with a constant velocity and temperature enters the channel. The results show that the power output, voltage, and thermal efficiency of 36 rectangular configurations are higher than other flow channels. Also, the heat input, power output, and thermal efficiency at a cross-sectional area ratio of 0.28 are respectively found to be 1.68, 1.77, and 1.52 times higher than at a cross-sectional area ratio of 0.68. In addition, an optimal length for a semiconductor is determined, in which the maximum output power is achieved.Thermoelectric generators are a sustainable and environmentally friendly technology that can recover wasted heat energy and convert it to electricity. Meanwhile, integrated thermoelectric generators have been able to significantly increase the performance of thermoelectric generators. In this paper, the effect of flow channel cross-sections on integrated thermoelectric power generator performance is investigated numerically using the finite volume method. In this regard, various flow channel configurations including circles, trapezoids, squares, and rectangles have been taken into account and the effect of cross-sectional area ratio, semiconductor length, and Reynolds number on the performance of the device has been evaluated. In this study, the top and bottom of conductor surfaces are exposed to a cold temperature and a hot fluid with a constant velocity and temperature enters the channel. The results show that the power output, voltage, and thermal efficiency of 36 rectangular configurations are higher than other flow channels. Also, the heat input, power output, and thermal efficiency at a cross-sectional area ratio of 0.28 are respectively found to be 1.68, 1.77, and 1.52 times higher than at a cross-sectional area ratio of 0.68. In addition, an optimal length for a semiconductor is determined, in which the maximum output power is achieved.https://mej.aut.ac.ir/article_4936_55071216b8447c71cb1335e06041df2e.pdf