majid nikfar - Academia.edu (original) (raw)

Papers by majid nikfar

Research paper thumbnail of A review study on the capacitive desalination set, and experimental fasibility study on coupling of FCDI and solar energy

Energy Engineering Management, 2020

Research paper thumbnail of The Effect of Inlet Condition on the Combustion in a Porous–Free Flame Burner

Research paper thumbnail of Numerical study of the effect of thermal boundary conditions and porous medium properties on the combustion in a combined porous-free flame burner

Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy

The effect of wall thermal conditions, pre-heating of the inlet air–fuel mixture ( Tin), and pore... more The effect of wall thermal conditions, pre-heating of the inlet air–fuel mixture ( Tin), and pore density of the porous medium (λ) on the stability limit and NO emission in a porous-free flame burner is numerically investigated. A reduced chemical mechanism and realizable k-ɛ turbulence model are used for the simulation. The numerical simulation is validated with the experimental data. The results show that the flame stability limit is extended with increasing the pore density while the maximum and minimum NO emissions are produced in pore densities of 8 ppc and 16 ppc, respectively. It is observed that the use of insulated wall condition causes the flame blow-off to occur at higher inlet velocities compared to that of the constant wall temperature condition. On the other hand, the use of constant wall temperature condition (cooled wall), causes flashback to occur in lower inlet velocities compared to that of the insulated wall. Constant wall temperature condition decreases NO emiss...

Research paper thumbnail of Entropy generation of Cu–water nanofluid mixed convection in a cavity

European Journal of Mechanics - B/Fluids, 2013

In this numerical work, mixed convection and entropy generation of Cu–water nanofluid and pure wa... more In this numerical work, mixed convection and entropy generation of Cu–water nanofluid and pure water in a lid-driven square cavity have been studied. Horizontal walls of the cavity are adiabatic and vertical walls have constant temperature but different values. The top wall has been considered as moving from left to right at a constant speed, U0U0. Rayleigh numbers of 104,105104,105 and 106106 and Reynolds numbers of 1, 10 and 100 have been considered. The results have shown that addition of nanoparticles to the base fluid affects the entropy generation, flow pattern and thermal behavior especially at higher Rayleigh and low Reynolds numbers. For pure fluid as well as nanofluid, increasing Reynolds number increases the average Nusselt number, linearly. The maximum entropy generation occurs in nanofluid at low Rayleigh number but high Reynolds number. The minimum entropy generation occurs in pure fluid at low Rayleigh and low Reynolds numbers. For the cases studied, at Rayleigh numbe...

Research paper thumbnail of Experimental study of operating range and radiation efficiency of a metal porous burner

Journal of Thermal Science, 2013

In this paper, a radiant metal porous burner which is formed from wire mesh layers is studied. Su... more In this paper, a radiant metal porous burner which is formed from wire mesh layers is studied. Surface temperature of the burner is measured in different equivalence ratios and firing rates and radiation efficiency is calculated for each case. The experiments are performed for different thicknesses of the porous medium. The results show that the surface temperature increases with increasing firing rate and maximum surface temperature occurs in a lean mixture. Comparing the results for different thicknesses shows that maximum surface temperature is obtained in a medium with three-layer of wire mesh. The radiation efficiency of the burner decreases with increasing firing rate. The maximum radiation efficiency is about 30 percent which is obtained in three-layer of wire mesh in the minimum firing rate. Comparison of the results with the other works shows a good agreement between them.

Research paper thumbnail of Aspect ratio effects of an adiabatic rectangular obstacle on natural convection and entropy generation of a nanofluid in an enclosure

Journal of Mechanical Science and Technology

ABSTRACT

Research paper thumbnail of Numerical study of natural convection and entropy generation of Cu-water nanofluid around an obstacle in a cavity

Journal of Mechanical Science and Technology

In this work, natural convection and entropy generation in a square cavity with an obstacle fille... more In this work, natural convection and entropy generation in a square cavity with an obstacle filled with Cu-water nanofluid is numerically studied. Horizontal walls of the cavity are adiabatic and vertical walls are maintained at a different constant temperature. The study has been done for the Rayleigh numbers between 10 3 and 10 6 , the obstacle dimensions (W/L) of 0.1-0.5 and for base fluid as well as nanofluid. It is found that, using the nanofluid overall leads to increase the flow strength, Nusselt number and entropy generation and decrease the Bejan number especially at high Rayleigh numbers. It is observed that by increasing the obstacle dimensions, the entropy generation increases and the Bejan number decreases, but the effect of the obstacle dimensions on Nusselt number depends on Rayleigh number. For the present thermal system, the increasing Nusselt number compared to increasing entropy generation due to increase obstacle dimensions is significant at low Rayleigh numbers.

Research paper thumbnail of Numerical Investigation of Nanofluid Mixed Convection and Entropy Generation in an Inclined Ventilating Cavity

Research paper thumbnail of Numerical investigation of Cu-water nanofluid natural convection and entropy generation within a cavity with an embedded conductive baffle

ABSTRACT This article presents a numerical study of natural convection and entropy generation of ... more ABSTRACT This article presents a numerical study of natural convection and entropy generation of Cu-water nanofluid within an enclosure with a conductive baffle embedded on bottom hot wall. The governing equations are solved numerically with Finite Volume Method using the SIMPLER algorithm. Effects of Rayleigh number, position of conductive baffle and volume fraction of nanoparticles on the streamlines, isotherms, mean Nusselt number, entropy generation, Bejan number and irreversibility factor have been studied. At Ra=104Ra=104 the convection heat transfer is very weak and the dominant conduction weakens by displacing the baffle toward the center of the cavity, thus the mean Nusselt number decreases. At higher Rayleigh numbers due to enhanced convection, the improved mean Nusselt number increases by increasing the volume fraction and displacing the baffle toward the center of the cavity. The effect of volume fraction and position of the baffle on entropy generation and Bejan number at Ra=104Ra=104 is different from Ra=105Ra=105 and 106106. This is due to the effects of addition of nanoparticles on the effective viscosity and conductivity of nanofluid and conduction dominance. It has been shown that assuming a constant irreversibility factor, χχ, with change of Ra and φφ is not correct.

Research paper thumbnail of Numerical investigation of NOx reduction in a sudden-expansion combustor with inclined turbulent air jet

Journal of Mechanical Science and Technology, 2012

Axisymmetric sudden-expansion geometry of a co-flowing methane-air diffusion flame is considered ... more Axisymmetric sudden-expansion geometry of a co-flowing methane-air diffusion flame is considered to investigate the effect of air inlet conditions on NO x formation, flow field and temperature distribution using the k-ε turbulence and β-PDF combustion model. The predicted results are in acceptable agreement with the published experimental and numerical data. The obtained results show that increasing air turbulence intensity results in considerable decrease in NO formation. Increasing the inlet angle of the air causes the NO formation to decrease due to raising vorticity strength. As a new index, the mass-averaged integral of vorticity magnitude is introduced to investigate the effect of altering inlet angle of the air on the flow field.

Research paper thumbnail of A review study on the capacitive desalination set, and experimental fasibility study on coupling of FCDI and solar energy

Energy Engineering Management, 2020

Research paper thumbnail of The Effect of Inlet Condition on the Combustion in a Porous–Free Flame Burner

Research paper thumbnail of Numerical study of the effect of thermal boundary conditions and porous medium properties on the combustion in a combined porous-free flame burner

Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy

The effect of wall thermal conditions, pre-heating of the inlet air–fuel mixture ( Tin), and pore... more The effect of wall thermal conditions, pre-heating of the inlet air–fuel mixture ( Tin), and pore density of the porous medium (λ) on the stability limit and NO emission in a porous-free flame burner is numerically investigated. A reduced chemical mechanism and realizable k-ɛ turbulence model are used for the simulation. The numerical simulation is validated with the experimental data. The results show that the flame stability limit is extended with increasing the pore density while the maximum and minimum NO emissions are produced in pore densities of 8 ppc and 16 ppc, respectively. It is observed that the use of insulated wall condition causes the flame blow-off to occur at higher inlet velocities compared to that of the constant wall temperature condition. On the other hand, the use of constant wall temperature condition (cooled wall), causes flashback to occur in lower inlet velocities compared to that of the insulated wall. Constant wall temperature condition decreases NO emiss...

Research paper thumbnail of Entropy generation of Cu–water nanofluid mixed convection in a cavity

European Journal of Mechanics - B/Fluids, 2013

In this numerical work, mixed convection and entropy generation of Cu–water nanofluid and pure wa... more In this numerical work, mixed convection and entropy generation of Cu–water nanofluid and pure water in a lid-driven square cavity have been studied. Horizontal walls of the cavity are adiabatic and vertical walls have constant temperature but different values. The top wall has been considered as moving from left to right at a constant speed, U0U0. Rayleigh numbers of 104,105104,105 and 106106 and Reynolds numbers of 1, 10 and 100 have been considered. The results have shown that addition of nanoparticles to the base fluid affects the entropy generation, flow pattern and thermal behavior especially at higher Rayleigh and low Reynolds numbers. For pure fluid as well as nanofluid, increasing Reynolds number increases the average Nusselt number, linearly. The maximum entropy generation occurs in nanofluid at low Rayleigh number but high Reynolds number. The minimum entropy generation occurs in pure fluid at low Rayleigh and low Reynolds numbers. For the cases studied, at Rayleigh numbe...

Research paper thumbnail of Experimental study of operating range and radiation efficiency of a metal porous burner

Journal of Thermal Science, 2013

In this paper, a radiant metal porous burner which is formed from wire mesh layers is studied. Su... more In this paper, a radiant metal porous burner which is formed from wire mesh layers is studied. Surface temperature of the burner is measured in different equivalence ratios and firing rates and radiation efficiency is calculated for each case. The experiments are performed for different thicknesses of the porous medium. The results show that the surface temperature increases with increasing firing rate and maximum surface temperature occurs in a lean mixture. Comparing the results for different thicknesses shows that maximum surface temperature is obtained in a medium with three-layer of wire mesh. The radiation efficiency of the burner decreases with increasing firing rate. The maximum radiation efficiency is about 30 percent which is obtained in three-layer of wire mesh in the minimum firing rate. Comparison of the results with the other works shows a good agreement between them.

Research paper thumbnail of Aspect ratio effects of an adiabatic rectangular obstacle on natural convection and entropy generation of a nanofluid in an enclosure

Journal of Mechanical Science and Technology

ABSTRACT

Research paper thumbnail of Numerical study of natural convection and entropy generation of Cu-water nanofluid around an obstacle in a cavity

Journal of Mechanical Science and Technology

In this work, natural convection and entropy generation in a square cavity with an obstacle fille... more In this work, natural convection and entropy generation in a square cavity with an obstacle filled with Cu-water nanofluid is numerically studied. Horizontal walls of the cavity are adiabatic and vertical walls are maintained at a different constant temperature. The study has been done for the Rayleigh numbers between 10 3 and 10 6 , the obstacle dimensions (W/L) of 0.1-0.5 and for base fluid as well as nanofluid. It is found that, using the nanofluid overall leads to increase the flow strength, Nusselt number and entropy generation and decrease the Bejan number especially at high Rayleigh numbers. It is observed that by increasing the obstacle dimensions, the entropy generation increases and the Bejan number decreases, but the effect of the obstacle dimensions on Nusselt number depends on Rayleigh number. For the present thermal system, the increasing Nusselt number compared to increasing entropy generation due to increase obstacle dimensions is significant at low Rayleigh numbers.

Research paper thumbnail of Numerical Investigation of Nanofluid Mixed Convection and Entropy Generation in an Inclined Ventilating Cavity

Research paper thumbnail of Numerical investigation of Cu-water nanofluid natural convection and entropy generation within a cavity with an embedded conductive baffle

ABSTRACT This article presents a numerical study of natural convection and entropy generation of ... more ABSTRACT This article presents a numerical study of natural convection and entropy generation of Cu-water nanofluid within an enclosure with a conductive baffle embedded on bottom hot wall. The governing equations are solved numerically with Finite Volume Method using the SIMPLER algorithm. Effects of Rayleigh number, position of conductive baffle and volume fraction of nanoparticles on the streamlines, isotherms, mean Nusselt number, entropy generation, Bejan number and irreversibility factor have been studied. At Ra=104Ra=104 the convection heat transfer is very weak and the dominant conduction weakens by displacing the baffle toward the center of the cavity, thus the mean Nusselt number decreases. At higher Rayleigh numbers due to enhanced convection, the improved mean Nusselt number increases by increasing the volume fraction and displacing the baffle toward the center of the cavity. The effect of volume fraction and position of the baffle on entropy generation and Bejan number at Ra=104Ra=104 is different from Ra=105Ra=105 and 106106. This is due to the effects of addition of nanoparticles on the effective viscosity and conductivity of nanofluid and conduction dominance. It has been shown that assuming a constant irreversibility factor, χχ, with change of Ra and φφ is not correct.

Research paper thumbnail of Numerical investigation of NOx reduction in a sudden-expansion combustor with inclined turbulent air jet

Journal of Mechanical Science and Technology, 2012

Axisymmetric sudden-expansion geometry of a co-flowing methane-air diffusion flame is considered ... more Axisymmetric sudden-expansion geometry of a co-flowing methane-air diffusion flame is considered to investigate the effect of air inlet conditions on NO x formation, flow field and temperature distribution using the k-ε turbulence and β-PDF combustion model. The predicted results are in acceptable agreement with the published experimental and numerical data. The obtained results show that increasing air turbulence intensity results in considerable decrease in NO formation. Increasing the inlet angle of the air causes the NO formation to decrease due to raising vorticity strength. As a new index, the mass-averaged integral of vorticity magnitude is introduced to investigate the effect of altering inlet angle of the air on the flow field.