Amirkabir University of Technology Amirkabir Journal of Mechanical Engineering 2008-6032 54 7 2022 09 23 Numerical Modeling of Diaphragm Dosing Pumps with Fluid-Structure Interaction Analysis Numerical Modeling of Diaphragm Dosing Pumps with Fluid-Structure Interaction Analysis 1461 1480 4784 10.22060/mej.2022.20658.7288 FA Rafat Mohammadi Department of Mechanical Engineering, Faculty of Engineering, Arak University, Arak, Iran Arefe Rabiee Kerahrudib Department of Mechanical Engineering, Faculty of Engineering, Arak University, Arak, Iran Amiir Ahmadi Department of Mechanical Engineering, Faculty of Engineering, Arak University, Arak, Iran Journal Article 2021 10 11 In this paper, the performance of a diaphragm dosing pump of the injection odorizers is simulated with the fluid-structure interaction analysis. The simulation results are validated with experimental data and the largest relative error is 16% for the average flow rate. Performance simulation of the diaphragm pump for the diaphragm oscillation period of 1 second and three different diaphragm displacement amplitudes of 0.8, 0.5, and 0.2 mm, shows that as the amplitude increases, the fluid velocity and consequently the flow rate of the pump increases. The average flow rate of the pump in the mentioned amplitudes is equal to 0.002, 0.0013, and 0.0005 kg/s, respectively. As the amplitude increases from 0.2 to 0.8 mm, the maximum stress applied to the diaphragm increases from 32.2 to 99.2 MPa (equivalent to 208%). Also, the effect of diaphragm oscillation frequency on pump performance is investigated. The results show that the pump's flow rate directly and linearly relates to the diaphragm oscillation frequency. In contrast, the applied stress on the diaphragm is not frequency-dependent and in the same ratios of the period, the applied stress is almost constant. According to the results, if the pump amplitude is set to 0.5 mm and the frequency is 1.6 Hz, instead of operating at a diaphragm amplitude of 0.8 mm and a frequency of 1 Hz, the pump's flow rate will be the same. While the maximum amount of stress in the diaphragm will be reduced by about 30% and the probability of damage will be reduced. In this paper, the performance of a diaphragm dosing pump of the injection odorizers is simulated with the fluid-structure interaction analysis. The simulation results are validated with experimental data and the largest relative error is 16% for the average flow rate. Performance simulation of the diaphragm pump for the diaphragm oscillation period of 1 second and three different diaphragm displacement amplitudes of 0.8, 0.5, and 0.2 mm, shows that as the amplitude increases, the fluid velocity and consequently the flow rate of the pump increases. The average flow rate of the pump in the mentioned amplitudes is equal to 0.002, 0.0013, and 0.0005 kg/s, respectively. As the amplitude increases from 0.2 to 0.8 mm, the maximum stress applied to the diaphragm increases from 32.2 to 99.2 MPa (equivalent to 208%). Also, the effect of diaphragm oscillation frequency on pump performance is investigated. The results show that the pump's flow rate directly and linearly relates to the diaphragm oscillation frequency. In contrast, the applied stress on the diaphragm is not frequency-dependent and in the same ratios of the period, the applied stress is almost constant. According to the results, if the pump amplitude is set to 0.5 mm and the frequency is 1.6 Hz, instead of operating at a diaphragm amplitude of 0.8 mm and a frequency of 1 Hz, the pump's flow rate will be the same. While the maximum amount of stress in the diaphragm will be reduced by about 30% and the probability of damage will be reduced.

https://mej.aut.ac.ir/article_4784_5dedb42b34e50082065a783265ce28a8.pdf

Amirkabir University of Technology Amirkabir Journal of Mechanical Engineering 2008-6032 54 7 2022 09 23 Simulation of the Role of the Anti-Angiogenic Therapy in Fluid Flow Behavior and Macromolecule Transport into a Heterogeneous Solid Tumor Simulation of the Role of the Anti-Angiogenic Therapy in Fluid Flow Behavior and Macromolecule Transport into a Heterogeneous Solid Tumor 1481 1512 4800 10.22060/mej.2022.20938.7343 FA Mahya Mohammadi Department of Mechanical Engineering, K. N. Toosi University of Technology, Tehran, Iran Cyrus Aghanajafi Department of Mechanical Engineering, K. N. Toosi University of Technology, Tehran, Iran Majid Soltani Department of Mechanical Engineering, K. N. Toosi University of Technology, Tehran, Iran 0000-0003-0878-6274 Journal Article 2021 12 31 The present study develops a numerical approach based on the mathematical models governing the behavior of fluid flow and drug transport in tumors to investigate the delivery of a macromolecule under the effect of the vascular normalization into a non-uniform tumor, including different parts of a real solid tumor. In this study, different tumor sizes in the range of are considered. The area under the curves of the drug average distribution and its deviation in the tumor site over time is studied as the amount of drug delivered and the uniformity of delivered drug to assess the quality of drug delivery. Results show that before and after normalization, the behaviors of interstitial fluid flow and the distribution of therapeutic agent concentration depend on tumor size. Normalization in all sizes reduces the interstitial fluid pressure, which this pressure drop increases as the tumor size reduces. Normalization improves antibody concentration distribution at different times depending on tumor size. However, from the point of view of the average spatiotemporal criterion, vascular normalization improves macromolecule delivery into the tumor site in by increasing the distribution uniformity. This research, by discussing the mechanisms affecting normalization efficiency, can provide insights for in vivo and in vitro studies that address the combination of anti-angiogenic therapy and chemotherapy. The present study develops a numerical approach based on the mathematical models governing the behavior of fluid flow and drug transport in tumors to investigate the delivery of a macromolecule under the effect of the vascular normalization into a non-uniform tumor, including different parts of a real solid tumor. In this study, different tumor sizes in the range of are considered. The area under the curves of the drug average distribution and its deviation in the tumor site over time is studied as the amount of drug delivered and the uniformity of delivered drug to assess the quality of drug delivery. Results show that before and after normalization, the behaviors of interstitial fluid flow and the distribution of therapeutic agent concentration depend on tumor size. Normalization in all sizes reduces the interstitial fluid pressure, which this pressure drop increases as the tumor size reduces. Normalization improves antibody concentration distribution at different times depending on tumor size. However, from the point of view of the average spatiotemporal criterion, vascular normalization improves macromolecule delivery into the tumor site in by increasing the distribution uniformity. This research, by discussing the mechanisms affecting normalization efficiency, can provide insights for in vivo and in vitro studies that address the combination of anti-angiogenic therapy and chemotherapy.

https://mej.aut.ac.ir/article_4800_0c4a4df48a930b56e7d71ec5a34b8257.pdf

Amirkabir University of Technology Amirkabir Journal of Mechanical Engineering 2008-6032 54 7 2022 09 23 Acoustic Simulation of Hot and Cold Flow mixing by a Lobed Mixer in a High Bypass Ratio Turbofan Engine Acoustic Simulation of Hot and Cold Flow mixing by a Lobed Mixer in a High Bypass Ratio Turbofan Engine 1513 1532 4823 10.22060/mej.2022.20701.7296 FA Sadegh Fazeli Malek Ashtar University Rouhollah Khoshkhoo Faculty of Mechanical Engineering, MUT Alireza Khoeini Poor Far PhD of Mechanical Engineering, Maintenance Engineering Department, Mapna Turbine Engineering and Manufacturing Company (TOGA) Journal Article 2021 10 23 Noise reduction laws for turbofan engines require effective configurations to reduce jet engine noise. Lobed mixers are known to be effective for noise reduction in high bypass ratio turbofan engines. In this study, a mixture of hot and cold flow is simulated in a lobed mixer for a high bypass ratio turbofan engine. Navier-Stokes equations are considered three-dimensional, compressible, steady, and turbulent. To solve the turbulent flow, the turbulent model has been used; besides, to investigate the acoustic power, the Broadband noise source model was applied. In this research, first, the simulation method was validated and the results were compared with the experimental data of previous studies. Then, the impact of the lobed mixer was investigated on mixing hot and cold flow and noise reduction in a high-bypass ratio turbofan engine. The results of this study show that the maximum acoustic power was obtained at about 72 dB at a distance of 14 meters from the nozzle, decreasing by moving away from the engine nozzle; also, the maximum amount of acoustic power in the central body at nozzle exit has decreased from about 90 dB to 72 dB. The maximum acoustic power was observed at about 95 dB on the mixer surface next to the central body flow. Finally, we can conclude that a mixture of flow reduces the acoustic power and improves its uniformity at the nozzle exit while increasing the acoustic power near the central body. Noise reduction laws for turbofan engines require effective configurations to reduce jet engine noise. Lobed mixers are known to be effective for noise reduction in high bypass ratio turbofan engines. In this study, a mixture of hot and cold flow is simulated in a lobed mixer for a high bypass ratio turbofan engine. Navier-Stokes equations are considered three-dimensional, compressible, steady, and turbulent. To solve the turbulent flow, the turbulent model has been used; besides, to investigate the acoustic power, the Broadband noise source model was applied. In this research, first, the simulation method was validated and the results were compared with the experimental data of previous studies. Then, the impact of the lobed mixer was investigated on mixing hot and cold flow and noise reduction in a high-bypass ratio turbofan engine. The results of this study show that the maximum acoustic power was obtained at about 72 dB at a distance of 14 meters from the nozzle, decreasing by moving away from the engine nozzle; also, the maximum amount of acoustic power in the central body at nozzle exit has decreased from about 90 dB to 72 dB. The maximum acoustic power was observed at about 95 dB on the mixer surface next to the central body flow. Finally, we can conclude that a mixture of flow reduces the acoustic power and improves its uniformity at the nozzle exit while increasing the acoustic power near the central body.

https://mej.aut.ac.ir/article_4823_0f089a3bcf38d052f7882d12b3923a82.pdf

Amirkabir University of Technology Amirkabir Journal of Mechanical Engineering 2008-6032 54 7 2022 09 23 Numerical Investigation of Internal Flow Transition Using Modified γ-Reθ Model Numerical Investigation of Internal Flow Transition Using Modified γ-Reθ Model 1533 1552 4818 10.22060/mej.2022.21138.7383 FA Mohamad Ali Modaresi Tarbiat Modares University, Tehran, Iran Ghassem Heidarinejad Faculty of Mechanical Engineering, Tarbiat Modares University, Tehran, Iran Reza Maddahian Faculty of Mechanical Engineering, Tarbiat Modares University, Tehran, Iran Bahar Firoozabadi Sharif University of Technology Journal Article 2022 02 22 The numerical investigation of Transition is one of the challenging issues in turbulence modeling. In the present study, the coefficients of the γ-Reθ model are modified based on the physics of internal flow transition to capture the entrance length properly. To validate the model, the internal flow is simulated using six test cases. A 3D duct, two smooth axisymmetric pipes, a 3D stenosis pipe, two parallel plates, and the backward-facing step configurations are considered at different Reynolds numbers from 2´103 to 3´105. The flow variables, including the average velocity field, friction factor, fully developed friction factor, and the reattachment length are compared against the experimental, theoretical and large eddy simulation results. By comparing the results of average velocity against the semi-empirical relations and experimental data using new coefficients, it is observed the model can estimate the entrance length in accordance with experiments. The earlier coefficients lead to a reduction of entrance length by increasing the Reynolds number. Furthermore, the error percentages reduce by more than 7.6 and 26.7 percent using new coefficients rather than earlier models for fully developed friction factor and reattachment length, respectively. The numerical investigation of Transition is one of the challenging issues in turbulence modeling. In the present study, the coefficients of the γ-Reθ model are modified based on the physics of internal flow transition to capture the entrance length properly. To validate the model, the internal flow is simulated using six test cases. A 3D duct, two smooth axisymmetric pipes, a 3D stenosis pipe, two parallel plates, and the backward-facing step configurations are considered at different Reynolds numbers from 2´103 to 3´105. The flow variables, including the average velocity field, friction factor, fully developed friction factor, and the reattachment length are compared against the experimental, theoretical and large eddy simulation results. By comparing the results of average velocity against the semi-empirical relations and experimental data using new coefficients, it is observed the model can estimate the entrance length in accordance with experiments. The earlier coefficients lead to a reduction of entrance length by increasing the Reynolds number. Furthermore, the error percentages reduce by more than 7.6 and 26.7 percent using new coefficients rather than earlier models for fully developed friction factor and reattachment length, respectively.

https://mej.aut.ac.ir/article_4818_e88f243bf341ded9b4ced444795c3f17.pdf

Amirkabir University of Technology Amirkabir Journal of Mechanical Engineering 2008-6032 54 7 2022 09 23 Advanced Exergy Investigation of Combined Cycle of Helium Reactor Gas Turbine with Organic Rankine Cycle Advanced Exergy Investigation of Combined Cycle of Helium Reactor Gas Turbine with Organic Rankine Cycle 1553 1574 4795 10.22060/mej.2022.20637.7284 FA Mohsen Fallah Mechanical engineering group, Azarbaijan Shahid Madani University Zahra Mohammadi Tabriz university Seyed Mohammad Seyed Mahmoudi Tabriz university Journal Article 2021 10 06 In this work, the combined cycle of a helium reactor gas turbine with an organic Rankine cycle is studied and compared from the perspective of conventional and advanced exergy analysis. Using Equation solving engineering software, modeling of this cycle has been done and the results of conventional energy and exergy analysis have been obtained. Then, to determine the appropriate prioritization of cycle component improvement from the perspective of advanced exergy analysis has been studied. In fact, advanced exergy analysis provides accurate information about the real potential for system performance improvement by dividing the exergy destruction of each component into endogenous, exogenous, avoidable, and unavoidable components. The results of advanced exergy analysis show that by modifying and upgrading the components of the system, 19.1% of the total exergy destruction of the system can be reduced. According to the advanced exergy analysis, the improvement priority belongs to the compressor and then to the reactor and gas turbine. However, from the conventional exergy analysis, the reactor's exergy destruction is greater than that of the compressor and the priority is on the reactor. In addition, based on the prioritization of advanced exergy analysis, it is possible to increase the cycle exergy efficiency from 75.21% to 82.51% and the cycle energy efficiency from 51% to 56.22%. In this work, the combined cycle of a helium reactor gas turbine with an organic Rankine cycle is studied and compared from the perspective of conventional and advanced exergy analysis. Using Equation solving engineering software, modeling of this cycle has been done and the results of conventional energy and exergy analysis have been obtained. Then, to determine the appropriate prioritization of cycle component improvement from the perspective of advanced exergy analysis has been studied. In fact, advanced exergy analysis provides accurate information about the real potential for system performance improvement by dividing the exergy destruction of each component into endogenous, exogenous, avoidable, and unavoidable components. The results of advanced exergy analysis show that by modifying and upgrading the components of the system, 19.1% of the total exergy destruction of the system can be reduced. According to the advanced exergy analysis, the improvement priority belongs to the compressor and then to the reactor and gas turbine. However, from the conventional exergy analysis, the reactor's exergy destruction is greater than that of the compressor and the priority is on the reactor. In addition, based on the prioritization of advanced exergy analysis, it is possible to increase the cycle exergy efficiency from 75.21% to 82.51% and the cycle energy efficiency from 51% to 56.22%.

https://mej.aut.ac.ir/article_4795_adf7ee2dcf142b0e11888e72b43fcb75.pdf

Amirkabir University of Technology Amirkabir Journal of Mechanical Engineering 2008-6032 54 7 2022 09 23 Investigating the Effect of Mesh Structure and Mesh Retaining Module on the Rate of Fog Harvesting Investigating the Effect of Mesh Structure and Mesh Retaining Module on the Rate of Fog Harvesting 1575 1586 4799 10.22060/mej.2022.20812.7320 FA Amir Reza Mohebi Faculty of Chemical Engineering, Amirkabir University of Technology, Tehran, Iran. Mehrdad Mozaffarian Faculty of Chemical Engineering, Amirkabir University of Technology, Tehran, Iran. 0000-0003-1030-2953 Mohammad Karimi Faculty of Textile Engineering, Amirkabir University of Technology, Tehran, Iran. Journal Article 2021 11 24 Nowadays, the impact of water scarcity is felt more than ever due to population growth, environmental changes, and increased industrial as well as agricultural developments. Thus, it is imperative to harvest water from every available source such as fog. The process of harvesting water from fog which is a cost-effective method has attracted the attention of many researchers trying to increase the efficiency of this method in various ways. In this research, a practical test system is presented to investigate the influence of the mesh and the mesh retaining module on the rate of fog harvesting. 6 sets of modules and meshes were exposed to the fog flow and after taking the results, the most effective factor between the meshes and the module was determined. All factors affecting fog harvesting were kept constant during the test, and only the effects of the mesh and module were examined. Teflon yarns mesh which increased the fog harvesting by 23 to 77%, was chosen as the best mesh, while the Modular Funnel-Large Fog Collector module which increased the rate of fog collection by 7 to 9 times was considered as the best module. This unique effectiveness should be attributed to the aerodynamic property of the MF-LFC module, which uses the rate of fog flow effectively in order to increase water harvesting. Nowadays, the impact of water scarcity is felt more than ever due to population growth, environmental changes, and increased industrial as well as agricultural developments. Thus, it is imperative to harvest water from every available source such as fog. The process of harvesting water from fog which is a cost-effective method has attracted the attention of many researchers trying to increase the efficiency of this method in various ways. In this research, a practical test system is presented to investigate the influence of the mesh and the mesh retaining module on the rate of fog harvesting. 6 sets of modules and meshes were exposed to the fog flow and after taking the results, the most effective factor between the meshes and the module was determined. All factors affecting fog harvesting were kept constant during the test, and only the effects of the mesh and module were examined. Teflon yarns mesh which increased the fog harvesting by 23 to 77%, was chosen as the best mesh, while the Modular Funnel-Large Fog Collector module which increased the rate of fog collection by 7 to 9 times was considered as the best module. This unique effectiveness should be attributed to the aerodynamic property of the MF-LFC module, which uses the rate of fog flow effectively in order to increase water harvesting.

https://mej.aut.ac.ir/article_4799_fecc3a370a23d13b1cf91ac3c1e1ca92.pdf

Amirkabir University of Technology Amirkabir Journal of Mechanical Engineering 2008-6032 54 7 2022 09 23 Numerical Investigation of Steam Methane Reforming over Ni- and Rh-based Catalysts to Produce Hydrogen, Syngas and Reduce Surface Coverage Numerical Investigation of Steam Methane Reforming over Ni- and Rh-based Catalysts to Produce Hydrogen, Syngas and Reduce Surface Coverage 1587 1606 4851 10.22060/mej.2022.20851.7331 FA Ali Saeedi University of Birjand 0000-0003-1950-6098 Fatemeh Zangooei Department of Mechanical Engineering, University of Birjand Journal Article 2021 12 15 Steam methane reforming has the highest efficiency compared with other hydrogen production ways. Temperature, pressure, steam to methane ratio, and catalyst play essential roles in the Steam methane reforming process. In this paper, a numerical simulation method is performed using Cantera software in Python programming language to produce syngas and hydrogen in the Steam methane reforming process over Nickel- and Rhodium-based catalysts. The simulation is done in 600-1300K, steam to methane ratio of 2-4, and pressure of 0.25-4 bars to determine a suitable catalyst and the best range to produce hydrogen and syngas and to reduce Carbone surface coverage. The results demonstrate that the preferred ranges for hydrogen production over Nickel and Rhodium are temperature between 1000 to 1100K, pressure 1 to 2 bars, and steam to methane ratio 2.5 to 3 and 3 to 3.5 for each, respectively. The appropriate ranges to produce syngas over Nickel and Rhodium are temperature 1200-1300K and 1100-1300K, steam to methane ratio 2.5-3 and 3-3.5, respectively, and the pressure is suggested between 1-2 bars. However, Rhodium in the same condition is more active than Nickel, while the surface coverage formation is lower over Nickel than Rhodium. Therefore, Nickel is proposed to produce hydrogen via Steam Methane Reforming. Steam methane reforming has the highest efficiency compared with other hydrogen production ways. Temperature, pressure, steam to methane ratio, and catalyst play essential roles in the Steam methane reforming process. In this paper, a numerical simulation method is performed using Cantera software in Python programming language to produce syngas and hydrogen in the Steam methane reforming process over Nickel- and Rhodium-based catalysts. The simulation is done in 600-1300K, steam to methane ratio of 2-4, and pressure of 0.25-4 bars to determine a suitable catalyst and the best range to produce hydrogen and syngas and to reduce Carbone surface coverage. The results demonstrate that the preferred ranges for hydrogen production over Nickel and Rhodium are temperature between 1000 to 1100K, pressure 1 to 2 bars, and steam to methane ratio 2.5 to 3 and 3 to 3.5 for each, respectively. The appropriate ranges to produce syngas over Nickel and Rhodium are temperature 1200-1300K and 1100-1300K, steam to methane ratio 2.5-3 and 3-3.5, respectively, and the pressure is suggested between 1-2 bars. However, Rhodium in the same condition is more active than Nickel, while the surface coverage formation is lower over Nickel than Rhodium. Therefore, Nickel is proposed to produce hydrogen via Steam Methane Reforming.

https://mej.aut.ac.ir/article_4851_5d40954183d62a82257835477ccad3d2.pdf

Amirkabir University of Technology Amirkabir Journal of Mechanical Engineering 2008-6032 54 7 2022 09 23 Numerical Study of Catalyst Bed Performance of a Monopropellant Thruster Under Influence of Porosity Coefficient Numerical Study of Catalyst Bed Performance of a Monopropellant Thruster Under Influence of Porosity Coefficient 1607 1622 4837 10.22060/mej.2022.20741.7305 FA Mohammadreza Salimi Ari Hadiseh Karimaei Ari Mostafa Gholampour Yazdi Ari Journal Article 2021 11 01 Hydrazine monopropellant thrusters are commonly used in the situation control and orbital transmission systems of satellites and space crafts. In these thrusters, hydrazine is decomposed into a hot gas product after passing through the catalyst bed during an exothermic reaction. The decomposition chamber of a monopropellant thruster is numerically modeled at the pore scale. Then the effect of catalyst bed porosity coefficient, which is the most important parameter affecting the performance of the decomposition chamber, is investigated. Simulations were performed in two-dimensional axial symmetry as the steady flow in the gas phase. Catalyst granules with an average diameter of 1 mm with three porosity coefficients of 0.4, 0.55, and 0.65 have been considered and the inlet pressure of the decomposition chamber has been considered to 15 bar. The results showed that the porosity coefficient has a very significant effect on the performance of the catalyst bed so that by decreasing this coefficient, the decomposition of hydrazine increases, the bed temperature, and outer wall temperature increase, and the mass flow rate decreases. Reducing the bed porosity coefficient from 0.65 to 0.4 causes about a 40% drop in the bed pressure compared to the initial inlet pressure and also about a 40% reduction in the mass flow rate through the bed. Therefore, the study of this parameter can greatly help the researchers in determining and optimizing the efficiency of the decomposition chamber. Hydrazine monopropellant thrusters are commonly used in the situation control and orbital transmission systems of satellites and space crafts. In these thrusters, hydrazine is decomposed into a hot gas product after passing through the catalyst bed during an exothermic reaction. The decomposition chamber of a monopropellant thruster is numerically modeled at the pore scale. Then the effect of catalyst bed porosity coefficient, which is the most important parameter affecting the performance of the decomposition chamber, is investigated. Simulations were performed in two-dimensional axial symmetry as the steady flow in the gas phase. Catalyst granules with an average diameter of 1 mm with three porosity coefficients of 0.4, 0.55, and 0.65 have been considered and the inlet pressure of the decomposition chamber has been considered to 15 bar. The results showed that the porosity coefficient has a very significant effect on the performance of the catalyst bed so that by decreasing this coefficient, the decomposition of hydrazine increases, the bed temperature, and outer wall temperature increase, and the mass flow rate decreases. Reducing the bed porosity coefficient from 0.65 to 0.4 causes about a 40% drop in the bed pressure compared to the initial inlet pressure and also about a 40% reduction in the mass flow rate through the bed. Therefore, the study of this parameter can greatly help the researchers in determining and optimizing the efficiency of the decomposition chamber.

https://mej.aut.ac.ir/article_4837_274a10ffa06e434f2a94df765cac6bf4.pdf

Amirkabir University of Technology Amirkabir Journal of Mechanical Engineering 2008-6032 54 7 2022 09 23 Investigation of Unsteady Thermal Performance of Multi-Effect Desalination with Thermal Vapor Compression Investigation of Unsteady Thermal Performance of Multi-Effect Desalination with Thermal Vapor Compression 1623 1646 4831 10.22060/mej.2022.20921.7337 FA Sobhan Khajehnamaghi Shahroud University of Technology, Shahroud, Iran Mohsen Nazari Mostafa Nazari Shahrood Univ. Omid Pilevar SUT Journal Article 2021 12 24 Due to the high use of thermal desalination plants, there is a great tendency to simulate their behavior. Most of the research is focused on modeling steady behavior, but to design control systems and evaluate their performance, we also need to study unsteady behavior. Also, few researchers have studied the system shutdown. In this paper, steady and unsteady modeling of an industrial multi-effect desalination plant with four effects, one condenser, and a Thermo compressor has been studied. The variable-step, variable-order method has been used to solve differential equations. Each evaporator is divided into three phases of vapor, tubes, and brine then the equations of mass and energy conservation are used. Results have been validated with real plant data. The variables of temperature, vapor flow rate, brine flow rate and brine level were studied in unsteady modeling in starting, shutting down, and steady-state conditions. It was found that the largest change in the brine flow rate after shutting down is in the last effect, which increases by 42%. Also, the biggest change in the level of the brine is in the first effect, which after 800 seconds will reach 11 times the steady state that will cause the flooding phenomenon. Due to the high use of thermal desalination plants, there is a great tendency to simulate their behavior. Most of the research is focused on modeling steady behavior, but to design control systems and evaluate their performance, we also need to study unsteady behavior. Also, few researchers have studied the system shutdown. In this paper, steady and unsteady modeling of an industrial multi-effect desalination plant with four effects, one condenser, and a Thermo compressor has been studied. The variable-step, variable-order method has been used to solve differential equations. Each evaporator is divided into three phases of vapor, tubes, and brine then the equations of mass and energy conservation are used. Results have been validated with real plant data. The variables of temperature, vapor flow rate, brine flow rate and brine level were studied in unsteady modeling in starting, shutting down, and steady-state conditions. It was found that the largest change in the brine flow rate after shutting down is in the last effect, which increases by 42%. Also, the biggest change in the level of the brine is in the first effect, which after 800 seconds will reach 11 times the steady state that will cause the flooding phenomenon.

https://mej.aut.ac.ir/article_4831_f720ec3e5486f090fd382b68e230b435.pdf

Amirkabir University of Technology Amirkabir Journal of Mechanical Engineering 2008-6032 54 7 2022 09 23 Numerical Investigation of Effective Parameters in Radiant Heat Transfer of Oxyfuel Combustion Process of Swirling Gas Furnaces Numerical Investigation of Effective Parameters in Radiant Heat Transfer of Oxyfuel Combustion Process of Swirling Gas Furnaces 1647 1672 4824 10.22060/mej.2022.20957.7347 FA Saman Kasmaiee Turbulence and Two Phase Flow Laboratory, Amirkabir University of Technology (Tehran Polytechnic) Tehran, Iran Sahar Noori Siroos Kasmaiee Turbulence and Two Phase Flow Laboratory, Amirkabir University of Technology (Tehran Polytechnic) Tehran, Iran Journal Article 2022 01 04 In gas furnaces based on oxyfuel combustion, radiative heat transfer is an important part of the heat flux and plays an important role in the flame temperature distribution. Different parameters affect the radiant heat transfer of furnaces. In this study, the effect of wall emissivity coefficient, oxidizer compound, and inlet flow swirl number in a Harwell gas furnace was investigated. k-ε standard, discrete ordinate, and eddy dissipation model were utilized to model turbulence, radiation, and combustion process, respectively. The radiative properties of the gaseous medium were determined using the weighted-sum-of-gray-gases model. The results showed that with increasing the swirl number, the maximum flame temperature moves upwards and approaches the inlet. This causes the heat flux of the walls to increase and the axial heat flux to decrease. By changing the oxidizer composition, the radiant activity of the gaseous medium changes. This causes a change in the temperature distribution in the whole field and axial and wall heat fluxes. The use of nitrogen in the oxidizer causes the maximum temperature to move towards the walls, while the use of carbon dioxide causes the flame to concentrate in the central axis, although the increase of the mass percentage of oxygen in the oxidizer improves flame diffusion. Increasing the wall emissivity coefficient causes the flame to become more concentrated and its maximum temperature to move upwards. In gas furnaces based on oxyfuel combustion, radiative heat transfer is an important part of the heat flux and plays an important role in the flame temperature distribution. Different parameters affect the radiant heat transfer of furnaces. In this study, the effect of wall emissivity coefficient, oxidizer compound, and inlet flow swirl number in a Harwell gas furnace was investigated. k-ε standard, discrete ordinate, and eddy dissipation model were utilized to model turbulence, radiation, and combustion process, respectively. The radiative properties of the gaseous medium were determined using the weighted-sum-of-gray-gases model. The results showed that with increasing the swirl number, the maximum flame temperature moves upwards and approaches the inlet. This causes the heat flux of the walls to increase and the axial heat flux to decrease. By changing the oxidizer composition, the radiant activity of the gaseous medium changes. This causes a change in the temperature distribution in the whole field and axial and wall heat fluxes. The use of nitrogen in the oxidizer causes the maximum temperature to move towards the walls, while the use of carbon dioxide causes the flame to concentrate in the central axis, although the increase of the mass percentage of oxygen in the oxidizer improves flame diffusion. Increasing the wall emissivity coefficient causes the flame to become more concentrated and its maximum temperature to move upwards.

https://mej.aut.ac.ir/article_4824_2edfeadfe636973b42d7b6ac315b896c.pdf

Amirkabir University of Technology Amirkabir Journal of Mechanical Engineering 2008-6032 54 7 2022 09 23 Development and Analysis of a Novel Multi-Generation System Fueled by Biogas with Smart Heat Recovery Development and Analysis of a Novel Multi-Generation System Fueled by Biogas with Smart Heat Recovery 1673 1700 4820 10.22060/mej.2022.20600.7269 FA Maryam Hassanzadeh UMA Hadi Ghaebi محقق اردبیلی-فنی و مهندسی- مهندسی مکانیک Milad Fili Mechanical Engineering Department Journal Article 2021 09 27 This paper presents a novel multi-generation system based on biogas fuel for simultaneous production of goods such as electricity, cooling, freshwater, and hydrogen using smart heat recovery of combustion gases. The performance of the proposed system is investigated in terms of the first and second laws of thermodynamics. Also, to acquire a comprehensive evaluation of operation costs, an exergoeconomic analysis has been performed. Furthermore, a comprehensive parametric study has been conducted to understand the behavior of the system performance parameters with the design parameters. In the following, to show the superiority of using a Stirling engine, the investigation of the present study is performed under two different scenarios. The proposed system could produce 986 kW, 137.5 kW, 8.39 m3/h, and 2.96 kg/h, net output electricity, cooling load, distilled water, and hydrogen while working with the Stirling engine. In this case, the energy and exergy efficiencies of the proposed system are obtained at 37.3% and 32.08%, which are improved by about 2.96% and 7.89%, respectively. In terms of cost metrics, the total unit cost of the products is about 0.1086$/kWh which has increased by 8.1% compared to the non-sterling engine mode. This paper presents a novel multi-generation system based on biogas fuel for simultaneous production of goods such as electricity, cooling, freshwater, and hydrogen using smart heat recovery of combustion gases. The performance of the proposed system is investigated in terms of the first and second laws of thermodynamics. Also, to acquire a comprehensive evaluation of operation costs, an exergoeconomic analysis has been performed. Furthermore, a comprehensive parametric study has been conducted to understand the behavior of the system performance parameters with the design parameters. In the following, to show the superiority of using a Stirling engine, the investigation of the present study is performed under two different scenarios. The proposed system could produce 986 kW, 137.5 kW, 8.39 m3/h, and 2.96 kg/h, net output electricity, cooling load, distilled water, and hydrogen while working with the Stirling engine. In this case, the energy and exergy efficiencies of the proposed system are obtained at 37.3% and 32.08%, which are improved by about 2.96% and 7.89%, respectively. In terms of cost metrics, the total unit cost of the products is about 0.1086$/kWh which has increased by 8.1% compared to the non-sterling engine mode.

https://mej.aut.ac.ir/article_4820_79cc30c73507cfc25d20fe7f7bcfd91b.pdf

Amirkabir University of Technology Amirkabir Journal of Mechanical Engineering 2008-6032 54 7 2022 09 23 Energy Harvesting from Pool Boiling Using Electromagnetic Induction: Experimental Study and Numerical Simulation Energy Harvesting from Pool Boiling Using Electromagnetic Induction: Experimental Study and Numerical Simulation 1701 1716 4856 10.22060/mej.2022.21002.7358 FA Rasool Maroofiazar Department of Mechanical Engineering, Faculty of Engineering, University of Maragheh, Maragheh, Iran 0000-0002-0746-4612 Maziar Fahimi Farzam Department of Civil Engineering, Faculty of Engineering, University of Maragheh, Maragheh, Iran. 0000-0001-9635-8186 Journal Article 2022 01 17 In this study, a method has been proposed for energy harvesting from waste heat. A magnet was floated on the liquid in the coiled container and the system was placed on the heat source. By pool boiling of the liquid and according to Faraday's induction law, the voltage was induced in the coil by the movement of the magnet. Excess temperature, dimensions of the container, liquid height in the container, and the frame shape and diameter have been selected as effective parameters. Effects of these parameters on peak-to-peak voltage and root mean square voltage have been investigated experimentally. Obtained results showed that the maximum energy was harvested at higher values of excess temperature, liquid height, coil turn, and frame diameter with a spherical frame shape. The highest measured parameters were 532 mV and 95.65 mV for Vpp and Vrms, respectively. In the second part, the numerical method is used to simulate the proposed system. The effect of various parameters on interface characteristics has been investigated. The results showed that the trend of changes in the interface parameters, including its pressure and height, were consistent with experimental data. Therefore, this method can be used to design and predict the performance of the energy harvester. In this study, a method has been proposed for energy harvesting from waste heat. A magnet was floated on the liquid in the coiled container and the system was placed on the heat source. By pool boiling of the liquid and according to Faraday's induction law, the voltage was induced in the coil by the movement of the magnet. Excess temperature, dimensions of the container, liquid height in the container, and the frame shape and diameter have been selected as effective parameters. Effects of these parameters on peak-to-peak voltage and root mean square voltage have been investigated experimentally. Obtained results showed that the maximum energy was harvested at higher values of excess temperature, liquid height, coil turn, and frame diameter with a spherical frame shape. The highest measured parameters were 532 mV and 95.65 mV for Vpp and Vrms, respectively. In the second part, the numerical method is used to simulate the proposed system. The effect of various parameters on interface characteristics has been investigated. The results showed that the trend of changes in the interface parameters, including its pressure and height, were consistent with experimental data. Therefore, this method can be used to design and predict the performance of the energy harvester.

https://mej.aut.ac.ir/article_4856_06f7c042b76e4b04f698c75b7b2777ea.pdf