Iman Zahmatkesh | Islamic Azad University, Mashhad Branch (original) (raw)

Papers by Iman Zahmatkesh

Numerical Heat Transfer, Part A: Applications

Journal of Mechanics, 2017

In this paper, unsteady flow and heat transfer of water flow in a backward-facing step under puls... more In this paper, unsteady flow and heat transfer of water flow in a backward-facing step under pulsating nanofluid blowing are studied numerically. Attention is focused to examine the impact of this type of blowing and its pertinent parameters on the heat transfer performance and to detect possible non-equilibrium between the base fluid and the nanoparticles inside the flow field. To this aim, the Eulerian-Eulerian two-phase model is adopted. This approach consists of separate equation sets for the base fluid and the nanoparticles. So, it provides details of the flow field for each of the constituents, separately. Computations are undertaken for different cases and the consequences of the frequency, amplitude, and the mean velocity of the pulsating blowing as well as the type, diameter, and the volume fraction of the nanoparticles therein on the heat transfer characteristics are analyzed. It is found that in addition to thermal conductivity of the blown nanoparticles, their penetratio...

Journal of energy storage, Jun 1, 2023

International Journal of Thermofluids

This paper deals with water flow in a backward-facing step with blowing of different nanofluids. ... more This paper deals with water flow in a backward-facing step with blowing of different nanofluids. The objective is to evaluate the effect of nanofluid blowing on the heat transfer rate. For this purpose, the Eulerian-Eulerian two-phase model is employed. The accuracy of the current simulations is demonstrated by comparing the obtained results with those of open literature. The results show that increasing the nanofluid blowing as well as nanoparticles fraction therein improves heat exchange from different surfaces of the channel. Comparing the results of different nanofluids leads one to conclude that the bottom wall heat transfer attains its maximum value when the blowed nanofluid contains nanoparticles with the highest thermal conductivity. However, it is found that maximum heat transfer in the top wall is achieved during blowing of a nanofluid with the highest nanoparticle penetration into the channel flow. Moreover, it is observed that discrepancies appearing between the results ...

Waves in Random and Complex Media

Applied Thermal Engineering, 2021

Abstract The thermal performance and response time of Thermal Energy Storage (TES) units are main... more Abstract The thermal performance and response time of Thermal Energy Storage (TES) units are mainly limited by the enclosure design and the low thermal conductivity of the storage medium. In the present study, the performance of petal-shape pipes in a shell and tube TES unit was numerically modeled and analyzed. The integration of the finite element method, a mesh adaptation approach, and an adaptive time-step scheme, was used to robustly simulate the phase change process and energy storage in the TES unit. The enclosure was considered fixed both dimensionally and by volume, which acts as a design constraint. The impacts of using two types of nano-additives, Cu and GO nanoparticles, and the geometrical aspects of the petal pipe on the thermal behavior of the TES unit were investigated. To find the optimal design of the TES unit with the maximum thermal energy power, the Taguchi optimization method was employed and a sensitivity analysis was performed. The copper nano-additives showed a better performance than the graphene oxide nano-additives. Although the surface area of the petal-pipe was fixed, its geometric shape was the most important parameter for maximizing the energy storage power of the TES unit. The optimum design could improve the amount of storage energy by 23.3% (Cu) and 22.5% (GO) NePCM compared to average designs. Based on an ANOVA analysis, the amplitude of petal shape could influence the total energy storage with a contribution ratio of about 41%, while the nanoparticles' contribution was 5-6%. An optimal design of a petal tube and Cu nanoparticles could improve the heat transfer by 45% compared to a circular tube with no nanoparticles.

The mixing pattern of two parallel gas streams initially separated by a splitter plate is analyze... more The mixing pattern of two parallel gas streams initially separated by a splitter plate is analyzed in this study. A recently proposed, two-fluid model is utilized for simulation of the flow field. The model provides separate balance equations for each component species of the system. As a consequence of the strong resemblance of the two-fluid model to the Navier-Stokes equations, the same numerical methods are applied to these new equations. The computations are undertaken for two-fluid systems; one with particles of about equal masses and another with particles of quite distinct masses, and the corresponding results are compared. This clarifies how the mass disparity of the constituents may affect the establishment of the flow field. The influence of molecular interaction descriptions in the model predictions is also examined by comparing the results of a hard-sphere model, the Maxwell repulsive potential, and the Lennard-Jones 12-6 potential.

In the present paper, the heatline visualization technique is utilized to understand heat transpo... more In the present paper, the heatline visualization technique is utilized to understand heat transport path for buoyancy-driven flow inside a rectangular porous enclosure saturated with nanofluids. For this purpose, the mass, momentum and energy conservation equations are solved numerically adopting a control-volume based computational procedure. Moreover, the dimensionless heat function equation is utilized to determine the heat flow pattern inside the enclosure. Computations are undertaken for Cu, Al2O3, and TiO2 nanoparticles in the base fluid of water and corresponding results in terms of dimensionless distributions of streamlines, isothermal lines, and heatlines as well as numerical values for flow strength and the average Nusselt number are compared with those of pure water under different Darcy-Rayleigh numbers. Additionally, the consequences of the nanoparticle fraction and the enclosure aspect ratio on the buoyancy-driven flow are analyzed. Inspection of the presented results ...

هلاقم تاعلاطا هدیکچ لماک یشهوژپ هلاقم :تفایرد 13 رویرهش 1396 :شریذپ 06 نابآ 1396 :تیاس رد هئارا 1... more هلاقم تاعلاطا هدیکچ لماک یشهوژپ هلاقم :تفایرد 13 رویرهش 1396 :شریذپ 06 نابآ 1396 :تیاس رد هئارا 10 رذآ 1396 هب هلاقم نیا تج قیرزت یسررب یاه یم بآ عطاقتم نایرج اب یلاناک رد لایسونان بروم ۀناگود ،اتسار نیا رد .دزادرپ فلتخم یاهرتماراپ رثا تج ۀیواز و هلصاف ،تعرس لماش یکیزیف و یسدنه نینچمه و اه نآ رد تارذونان یمجحرسک ، یم رارق هعلاطم دروم اه .دریگ لیلحت و هیزجت یارب ،رضاح ۀلأسم یرلوا یزافود لدم یم هتفرگ تمدخ هب یرلوا دوش یارب ازجم تلاداعم هعومجم لح اب درکیور نیا . ناکما ،تارذونان و هیاپ لایس شیپ ینیب هب ار اهزاف زا کی ره راتفر یم مهارف نایرج نادیم رد هناگادج روط .دنک هیبش تحص یزاس جیاتن اب لصاح جیاتن ۀسیاقم اب رضاح یاه یهاگشیامزآ یم تابثا هب دوجوم هب جیاتن .دسر یم ناشن هدمآ تسد هک دنهد هناگی تج ینیزگیاج تج اب یاه فده حطس زا ترارح لدابت ،هناگود ار تخاونکی هحفص لوط رد ار نآ عیزوت و هداد شیازفا یم رت یم صخشم ،نیا رب هولاع .دنک تج ۀلصاف و تعرس رد شیازفا هک دوش اه دوبهب .دراد یپ رد ار ترارح لاقتنا ،دوجو نیا اب هب تدش هب فده حطس زا ترارح لاقتنا خرن رب یقیرزت لایسونان رد دوجوم تارذونان یمجحرسک ...

Entropy generation of nanofluids during natural convection in rectangular porous enclosures is an... more Entropy generation of nanofluids during natural convection in rectangular porous enclosures is analyzed in this paper. The objective is to find optimum circumstances from the standpoints of the First Law and the Second Law of thermodynamics. For this purpose, the mass, momentum, and energy conservation equations are solved numerically. Thereafter, the generation of entropy is calculated and discussed. Computations are undertaken for Cu, Al2O3, and TiO2 nanoparticles in a base fluid of water and the corresponding results are compared. Moreover, the influences of volume fraction of the nanoparticles, Rayleigh number, enclosure aspect ratio, radiation exchange, and non-Darcy effects on heat transfer and entropy generation in the enclosure are analyzed. Inspection of the presented results demonstrates that radiation exchange and nonDarcy effects possess prominent consequences on heat transfer and entropy generation inside the enclosure. Among the current nanofluids, the highest heat tra...

Kuwait Journal of Science & Engineering, 2007

جستجو در مقالات دانشگاهی و کتب استادان دانشگاه فردوسی مشهد. ...

The recognition and mapping of rock facies is a pivotal step in reliable reservoir characterizati... more The recognition and mapping of rock facies is a pivotal step in reliable reservoir characterization and planning development operations. The present study aimed to present a practical workflow by integrating three-dimensional (3D) seismic attributes and well-log facies analysis to determine the spatial distribution of electrofacies rock types of the Oligo-Miocene Asmari reservoir in Mansuri oilfield located in the southwestern part of Iran. The workflow begins with integrating well logs, core data, and geological information from the selected ‘key wells’ to build an electrofacies model, which could help reservoir facies to be classified and estimated in the cored and uncored wells, respectively. In addition, a group of 3D seismic attribute volumes derived from amplitude, frequency, and time characteristics of the post-stacked 3D seismic data were identified to specify the heterogeneity of the vertical and lateral rock facies within the reservoir. Additionally, the seismic attributes...

Effect of a thin fin on natural convection heat transfer in a thermally stratified porous layer i... more Effect of a thin fin on natural convection heat transfer in a thermally stratified porous layer is analyzed in this study. For this purpose, the mass, momentum, and energy conservation equations are solved numerically adopting a control-volume based computational procedure. Computations are undertaken for several numerical values of the fin length and its position in various circumstances with different Rayleigh numbers, stratification parameters, and aspect ratios of the porous layer. Simulation results are compared in terms of distributions of streamlines and isothermal lines as well as numerical values of the average Nusselt number on the hot wall. It is found that the thin fin is of profound influences on the establishment of flow and thermal fields and possesses prominent consequences on heat transfer characteristics.

Iranian Journal of Science and Technology Transaction B-engineering, 2006

Abstract– The present study is concerned with the effect of fuel droplet size on the complex soot... more Abstract– The present study is concerned with the effect of fuel droplet size on the complex soot process in a turbulent liquid-fuelled combustor. A hybrid Eulerian-Lagrangian method is employed to model the reactive flowfield inside the combustor. Equations governing the gas phase are solved by a control-volume based semi-implicit iterative procedure, while the time-dependent differential equations for each size of the fuel droplets are integrated by a semi-analytic method. The processes leading to soot consist of both formation and combustion. Soot formation is simulated using a two-step model, while a finite rate combustion model with the eddy dissipation concept is implemented for soot combustion. Also, mathematical models for turbulence, combustion, and radiation are used to take into account the effects of these processes. Results reveal the significant influence of liquid fuel droplet size on soot emission from turbulent spray flames under different equivalence ratios, inlet ...

Several kinetic descriptions have already been utilized for the simulation of rare ed gas mixture... more Several kinetic descriptions have already been utilized for the simulation of rare ed gas mixture ows. Although such developments are important, Navier-Stokes computation can nd extended use in engineering applications. Recently, the authors have derived new velocity-slip and temperature-jump boundary conditions for slip ows of gas mixtures. Appealing to these new boundary conditions, Navier-Stokes computation of rare ed gas mixture problems has become feasible. In the present contribution, the proposed conditions, in conjunction with the Navier-Stokes equations and an equation for the conservation of species, are solved for some binary gas mixture problems in the slip ow regime. Applications include low pressure ow in a converging-diverging nozzle, wall-cooling of a nozzle under rare ed condition, and parallel mixing in a microchannel. Simulation results are presented in terms of the distributions of overall Knudsen number, Mach number, pressure, temperature, and concentration.

The present study is concerned with measuring and simulating soot formation and combustion in tur... more The present study is concerned with measuring and simulating soot formation and combustion in turbulent liquid fuel spray flames. Soot concentrations inside the combustor are measured by filter paper technique. The simulation is based on the solution of the fully-coupled conservation equations for turbulent flow, chemical species kinetic modeling, fuel droplet evaporation and combustion and soot formation/oxidation. The soot formation is modeled by using the soot particle number density and the mass density based on acetylene concentrations. Two oxidation models simulate the rate of soot combustion: the O 2-oxidation model, which assumes soot combustion is caused by oxygen molecules, and the O 2-OH oxidation model, which assumes soot combustion occurrs by both hydroxide radicals and oxygen molecules. The experimental and numerical investigations are conducted for different fuel spray cone angles. The comparison of calculated results against experimental measurements shows good agree...

Rapid development in nanotechnology has produced several aspects for the nanotechnologists to loo... more Rapid development in nanotechnology has produced several aspects for the nanotechnologists to look into. Nanofluid is one of the incredible outcomes of such advancement. They are best known for their remarkable change to enhanced heat transfer abilities. Viscosity is an important flow property of fluids that needs the same attention due to its very crucial impact on heat transfer. In the present work, viscosity of TiO2 nanofluids in saltwater are experimentally investigated to determine their applicability in different temperatures and volume fractions. All measurements have been done over a range of 20– 60°C for nanoparticle volumetric concentration of 0.05–0.8%. It was observed that the viscosity of the nanofluid increases with the increasing concentration of TiO2 in the nanofluid. Usually, typical used carrier fluids are water, organic liquids (ethylene glycol, oil, biological liquids, etc.), and polymer solutions and investigation of the nanofluid properties in salt-water as bas...

In the present work, forced convection heat transfer of slip flow in porous micro-tubes with loca... more In the present work, forced convection heat transfer of slip flow in porous micro-tubes with local thermal non-equilibrium between the gas and the solid matrix is investigated numerically. For this purpose, the flow is considered hydrodynamically developed but thermally developing. The Darcy-Brinkman-Forchheimer model in conjunction with separate energy equations for the gas and the solid matrix is used to describe the flow and heat transfer in the porous media. Moreover, both velocity slip and temperature jump are applied to the fluid at the wall. Simulation results are presented in terms of velocity field, distributions of the fluid and solid temperatures, the local Nusselt number, and the thermal entry length. The results indicate heat transfer improvement as a result of increase in the Peclet/Biot number. Increase in the Knudsen number or the modified conductivity ratio, however, diminishes the heat transfer rate. Although the choice of the Darcy/Forchheimer number may change th...

Numerical Heat Transfer, Part A: Applications

Journal of Mechanics, 2017

In this paper, unsteady flow and heat transfer of water flow in a backward-facing step under puls... more In this paper, unsteady flow and heat transfer of water flow in a backward-facing step under pulsating nanofluid blowing are studied numerically. Attention is focused to examine the impact of this type of blowing and its pertinent parameters on the heat transfer performance and to detect possible non-equilibrium between the base fluid and the nanoparticles inside the flow field. To this aim, the Eulerian-Eulerian two-phase model is adopted. This approach consists of separate equation sets for the base fluid and the nanoparticles. So, it provides details of the flow field for each of the constituents, separately. Computations are undertaken for different cases and the consequences of the frequency, amplitude, and the mean velocity of the pulsating blowing as well as the type, diameter, and the volume fraction of the nanoparticles therein on the heat transfer characteristics are analyzed. It is found that in addition to thermal conductivity of the blown nanoparticles, their penetratio...

Journal of energy storage, Jun 1, 2023

International Journal of Thermofluids

This paper deals with water flow in a backward-facing step with blowing of different nanofluids. ... more This paper deals with water flow in a backward-facing step with blowing of different nanofluids. The objective is to evaluate the effect of nanofluid blowing on the heat transfer rate. For this purpose, the Eulerian-Eulerian two-phase model is employed. The accuracy of the current simulations is demonstrated by comparing the obtained results with those of open literature. The results show that increasing the nanofluid blowing as well as nanoparticles fraction therein improves heat exchange from different surfaces of the channel. Comparing the results of different nanofluids leads one to conclude that the bottom wall heat transfer attains its maximum value when the blowed nanofluid contains nanoparticles with the highest thermal conductivity. However, it is found that maximum heat transfer in the top wall is achieved during blowing of a nanofluid with the highest nanoparticle penetration into the channel flow. Moreover, it is observed that discrepancies appearing between the results ...

Waves in Random and Complex Media

Applied Thermal Engineering, 2021

Abstract The thermal performance and response time of Thermal Energy Storage (TES) units are main... more Abstract The thermal performance and response time of Thermal Energy Storage (TES) units are mainly limited by the enclosure design and the low thermal conductivity of the storage medium. In the present study, the performance of petal-shape pipes in a shell and tube TES unit was numerically modeled and analyzed. The integration of the finite element method, a mesh adaptation approach, and an adaptive time-step scheme, was used to robustly simulate the phase change process and energy storage in the TES unit. The enclosure was considered fixed both dimensionally and by volume, which acts as a design constraint. The impacts of using two types of nano-additives, Cu and GO nanoparticles, and the geometrical aspects of the petal pipe on the thermal behavior of the TES unit were investigated. To find the optimal design of the TES unit with the maximum thermal energy power, the Taguchi optimization method was employed and a sensitivity analysis was performed. The copper nano-additives showed a better performance than the graphene oxide nano-additives. Although the surface area of the petal-pipe was fixed, its geometric shape was the most important parameter for maximizing the energy storage power of the TES unit. The optimum design could improve the amount of storage energy by 23.3% (Cu) and 22.5% (GO) NePCM compared to average designs. Based on an ANOVA analysis, the amplitude of petal shape could influence the total energy storage with a contribution ratio of about 41%, while the nanoparticles' contribution was 5-6%. An optimal design of a petal tube and Cu nanoparticles could improve the heat transfer by 45% compared to a circular tube with no nanoparticles.

The mixing pattern of two parallel gas streams initially separated by a splitter plate is analyze... more The mixing pattern of two parallel gas streams initially separated by a splitter plate is analyzed in this study. A recently proposed, two-fluid model is utilized for simulation of the flow field. The model provides separate balance equations for each component species of the system. As a consequence of the strong resemblance of the two-fluid model to the Navier-Stokes equations, the same numerical methods are applied to these new equations. The computations are undertaken for two-fluid systems; one with particles of about equal masses and another with particles of quite distinct masses, and the corresponding results are compared. This clarifies how the mass disparity of the constituents may affect the establishment of the flow field. The influence of molecular interaction descriptions in the model predictions is also examined by comparing the results of a hard-sphere model, the Maxwell repulsive potential, and the Lennard-Jones 12-6 potential.

In the present paper, the heatline visualization technique is utilized to understand heat transpo... more In the present paper, the heatline visualization technique is utilized to understand heat transport path for buoyancy-driven flow inside a rectangular porous enclosure saturated with nanofluids. For this purpose, the mass, momentum and energy conservation equations are solved numerically adopting a control-volume based computational procedure. Moreover, the dimensionless heat function equation is utilized to determine the heat flow pattern inside the enclosure. Computations are undertaken for Cu, Al2O3, and TiO2 nanoparticles in the base fluid of water and corresponding results in terms of dimensionless distributions of streamlines, isothermal lines, and heatlines as well as numerical values for flow strength and the average Nusselt number are compared with those of pure water under different Darcy-Rayleigh numbers. Additionally, the consequences of the nanoparticle fraction and the enclosure aspect ratio on the buoyancy-driven flow are analyzed. Inspection of the presented results ...

هلاقم تاعلاطا هدیکچ لماک یشهوژپ هلاقم :تفایرد 13 رویرهش 1396 :شریذپ 06 نابآ 1396 :تیاس رد هئارا 1... more هلاقم تاعلاطا هدیکچ لماک یشهوژپ هلاقم :تفایرد 13 رویرهش 1396 :شریذپ 06 نابآ 1396 :تیاس رد هئارا 10 رذآ 1396 هب هلاقم نیا تج قیرزت یسررب یاه یم بآ عطاقتم نایرج اب یلاناک رد لایسونان بروم ۀناگود ،اتسار نیا رد .دزادرپ فلتخم یاهرتماراپ رثا تج ۀیواز و هلصاف ،تعرس لماش یکیزیف و یسدنه نینچمه و اه نآ رد تارذونان یمجحرسک ، یم رارق هعلاطم دروم اه .دریگ لیلحت و هیزجت یارب ،رضاح ۀلأسم یرلوا یزافود لدم یم هتفرگ تمدخ هب یرلوا دوش یارب ازجم تلاداعم هعومجم لح اب درکیور نیا . ناکما ،تارذونان و هیاپ لایس شیپ ینیب هب ار اهزاف زا کی ره راتفر یم مهارف نایرج نادیم رد هناگادج روط .دنک هیبش تحص یزاس جیاتن اب لصاح جیاتن ۀسیاقم اب رضاح یاه یهاگشیامزآ یم تابثا هب دوجوم هب جیاتن .دسر یم ناشن هدمآ تسد هک دنهد هناگی تج ینیزگیاج تج اب یاه فده حطس زا ترارح لدابت ،هناگود ار تخاونکی هحفص لوط رد ار نآ عیزوت و هداد شیازفا یم رت یم صخشم ،نیا رب هولاع .دنک تج ۀلصاف و تعرس رد شیازفا هک دوش اه دوبهب .دراد یپ رد ار ترارح لاقتنا ،دوجو نیا اب هب تدش هب فده حطس زا ترارح لاقتنا خرن رب یقیرزت لایسونان رد دوجوم تارذونان یمجحرسک ...

Entropy generation of nanofluids during natural convection in rectangular porous enclosures is an... more Entropy generation of nanofluids during natural convection in rectangular porous enclosures is analyzed in this paper. The objective is to find optimum circumstances from the standpoints of the First Law and the Second Law of thermodynamics. For this purpose, the mass, momentum, and energy conservation equations are solved numerically. Thereafter, the generation of entropy is calculated and discussed. Computations are undertaken for Cu, Al2O3, and TiO2 nanoparticles in a base fluid of water and the corresponding results are compared. Moreover, the influences of volume fraction of the nanoparticles, Rayleigh number, enclosure aspect ratio, radiation exchange, and non-Darcy effects on heat transfer and entropy generation in the enclosure are analyzed. Inspection of the presented results demonstrates that radiation exchange and nonDarcy effects possess prominent consequences on heat transfer and entropy generation inside the enclosure. Among the current nanofluids, the highest heat tra...

Kuwait Journal of Science & Engineering, 2007

جستجو در مقالات دانشگاهی و کتب استادان دانشگاه فردوسی مشهد. ...

The recognition and mapping of rock facies is a pivotal step in reliable reservoir characterizati... more The recognition and mapping of rock facies is a pivotal step in reliable reservoir characterization and planning development operations. The present study aimed to present a practical workflow by integrating three-dimensional (3D) seismic attributes and well-log facies analysis to determine the spatial distribution of electrofacies rock types of the Oligo-Miocene Asmari reservoir in Mansuri oilfield located in the southwestern part of Iran. The workflow begins with integrating well logs, core data, and geological information from the selected ‘key wells’ to build an electrofacies model, which could help reservoir facies to be classified and estimated in the cored and uncored wells, respectively. In addition, a group of 3D seismic attribute volumes derived from amplitude, frequency, and time characteristics of the post-stacked 3D seismic data were identified to specify the heterogeneity of the vertical and lateral rock facies within the reservoir. Additionally, the seismic attributes...

Effect of a thin fin on natural convection heat transfer in a thermally stratified porous layer i... more Effect of a thin fin on natural convection heat transfer in a thermally stratified porous layer is analyzed in this study. For this purpose, the mass, momentum, and energy conservation equations are solved numerically adopting a control-volume based computational procedure. Computations are undertaken for several numerical values of the fin length and its position in various circumstances with different Rayleigh numbers, stratification parameters, and aspect ratios of the porous layer. Simulation results are compared in terms of distributions of streamlines and isothermal lines as well as numerical values of the average Nusselt number on the hot wall. It is found that the thin fin is of profound influences on the establishment of flow and thermal fields and possesses prominent consequences on heat transfer characteristics.

Iranian Journal of Science and Technology Transaction B-engineering, 2006

Abstract– The present study is concerned with the effect of fuel droplet size on the complex soot... more Abstract– The present study is concerned with the effect of fuel droplet size on the complex soot process in a turbulent liquid-fuelled combustor. A hybrid Eulerian-Lagrangian method is employed to model the reactive flowfield inside the combustor. Equations governing the gas phase are solved by a control-volume based semi-implicit iterative procedure, while the time-dependent differential equations for each size of the fuel droplets are integrated by a semi-analytic method. The processes leading to soot consist of both formation and combustion. Soot formation is simulated using a two-step model, while a finite rate combustion model with the eddy dissipation concept is implemented for soot combustion. Also, mathematical models for turbulence, combustion, and radiation are used to take into account the effects of these processes. Results reveal the significant influence of liquid fuel droplet size on soot emission from turbulent spray flames under different equivalence ratios, inlet ...

Several kinetic descriptions have already been utilized for the simulation of rare ed gas mixture... more Several kinetic descriptions have already been utilized for the simulation of rare ed gas mixture ows. Although such developments are important, Navier-Stokes computation can nd extended use in engineering applications. Recently, the authors have derived new velocity-slip and temperature-jump boundary conditions for slip ows of gas mixtures. Appealing to these new boundary conditions, Navier-Stokes computation of rare ed gas mixture problems has become feasible. In the present contribution, the proposed conditions, in conjunction with the Navier-Stokes equations and an equation for the conservation of species, are solved for some binary gas mixture problems in the slip ow regime. Applications include low pressure ow in a converging-diverging nozzle, wall-cooling of a nozzle under rare ed condition, and parallel mixing in a microchannel. Simulation results are presented in terms of the distributions of overall Knudsen number, Mach number, pressure, temperature, and concentration.

The present study is concerned with measuring and simulating soot formation and combustion in tur... more The present study is concerned with measuring and simulating soot formation and combustion in turbulent liquid fuel spray flames. Soot concentrations inside the combustor are measured by filter paper technique. The simulation is based on the solution of the fully-coupled conservation equations for turbulent flow, chemical species kinetic modeling, fuel droplet evaporation and combustion and soot formation/oxidation. The soot formation is modeled by using the soot particle number density and the mass density based on acetylene concentrations. Two oxidation models simulate the rate of soot combustion: the O 2-oxidation model, which assumes soot combustion is caused by oxygen molecules, and the O 2-OH oxidation model, which assumes soot combustion occurrs by both hydroxide radicals and oxygen molecules. The experimental and numerical investigations are conducted for different fuel spray cone angles. The comparison of calculated results against experimental measurements shows good agree...

Rapid development in nanotechnology has produced several aspects for the nanotechnologists to loo... more Rapid development in nanotechnology has produced several aspects for the nanotechnologists to look into. Nanofluid is one of the incredible outcomes of such advancement. They are best known for their remarkable change to enhanced heat transfer abilities. Viscosity is an important flow property of fluids that needs the same attention due to its very crucial impact on heat transfer. In the present work, viscosity of TiO2 nanofluids in saltwater are experimentally investigated to determine their applicability in different temperatures and volume fractions. All measurements have been done over a range of 20– 60°C for nanoparticle volumetric concentration of 0.05–0.8%. It was observed that the viscosity of the nanofluid increases with the increasing concentration of TiO2 in the nanofluid. Usually, typical used carrier fluids are water, organic liquids (ethylene glycol, oil, biological liquids, etc.), and polymer solutions and investigation of the nanofluid properties in salt-water as bas...

In the present work, forced convection heat transfer of slip flow in porous micro-tubes with loca... more In the present work, forced convection heat transfer of slip flow in porous micro-tubes with local thermal non-equilibrium between the gas and the solid matrix is investigated numerically. For this purpose, the flow is considered hydrodynamically developed but thermally developing. The Darcy-Brinkman-Forchheimer model in conjunction with separate energy equations for the gas and the solid matrix is used to describe the flow and heat transfer in the porous media. Moreover, both velocity slip and temperature jump are applied to the fluid at the wall. Simulation results are presented in terms of velocity field, distributions of the fluid and solid temperatures, the local Nusselt number, and the thermal entry length. The results indicate heat transfer improvement as a result of increase in the Peclet/Biot number. Increase in the Knudsen number or the modified conductivity ratio, however, diminishes the heat transfer rate. Although the choice of the Darcy/Forchheimer number may change th...

The first National Conference of New Technologies in Chemical and Chemical Engineering, 2013

The application of porous materials for the construction of electrical heaters is getting continu... more The application of porous materials for the construction of electrical heaters is getting continuing interest. Although general trends in porous electrical heaters can be deduced from characteristics of porous medium, the matter for certain geometries is not well studied yet. For this reason, in the present paper attention is focused on the analysis of thermal performance of some configurations of porous electrical heaters (i.e., with circular, rectangular, triangular, and trapezoidal cross-sections). To this aim, the conservation equations of the porous heat generating medium in conjunction with the corresponding boundary conditions are solved for these configurations and their results are compared.

3rd National Conference on Nanostructures, Nanoscience, and Nanoengineering, 2019

In the present paper, conjugate heat transfer (convection + conduction) of cu-water nanofluid ins... more In the present paper, conjugate heat transfer (convection + conduction) of cu-water nanofluid inside square porous enclosures is investigated. The enclosure has two vertical isothermal walls with finite thickness and two adiabatic walls. In the porous medium, Darcy's law is assumed to hold, the fluid and the porous matrix are in local thermal equilibrium. With these assumptions, the continuity, Darcy, and energy equations for steady and two-dimensional flow in an isotropic and homogeneous porous medium are solved by FORTRAN code using the finite-volume method. Computations are undertaken for Cu nanoparticle in a base fluid of water. The influences of the thickness of the vertical solid walls are analyzed for different Rayleigh number. Increasing the Rayleigh number or decreasing the thickness of walls enhances the average Nusselt number.

This paper focuses on the numerical simulation of turbulent combustion of methane in a two-dimens... more This paper focuses on the numerical simulation of turbulent combustion of methane in a two-dimensional porous media with wavy wall. The goal is to investigate the effect of wavy wall on premixed combustion in porous medium. For this purpose, the computations are undertaken for wavy as well as flat walls and the corresponding results are compared. Additionally, the effect of phase difference between the upper and lower wavy walls and also the impact of the amplitude of the sine wave are analyzed. The results show that wavy walls lead to temperature increase of the exhausted gas and the emission decrease of CO and unburned hydrocarbons. Controlling amplitude, minimum emission of unburned hydrocarbon, CO and NO occurs in 90 degree difference phase, and controlling the phase difference, amplitude increase co-occurs with decrease of CO and unburned hydrocarbons emission, temperature rise and NO emission increase.

Effect of thermal radiation on entropy generation in free convection inside inclined porous enclo... more Effect of thermal radiation on entropy generation in free convection inside inclined porous enclosures is analyzed in this study. The free convective flow is simulated by solving numerically the mass, momentum, and energy conservation equations invoking the Darcy’s law and the Oberbeck-Boussinesq approximation. Moreover, the Rosseland diffusion approximation is utilized to describe the radiative heat flux in the energy equation. The generation of entropy is also calculated taking into account both heat transfer irreversibility and fluid friction irreversibility. As thermal boundary conditions of the enclosures, two opposite walls are kept at constant but different temperatures whereas the other two are assumed to be adiabatic. Thereafter, it is discussed how thermal radiation may affect the establishment of flow and thermal fields as well as entropy generation characteristics inside enclosures with different inclination angles.