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1 – 10 of 63Rehena Nasrin, M.A. Alim and Ali J. Chamkha
This work is focused on the numerical modeling of mixed convective heat transfer in a double lid-driven cavity filled with water-CuO nanofluid in the presence of internal heat…
Abstract
Purpose
This work is focused on the numerical modeling of mixed convective heat transfer in a double lid-driven cavity filled with water-CuO nanofluid in the presence of internal heat generation. The paper aims to discuss these issues.
Design/methodology/approach
The flow field is modeled using a generalized form of the momentum and energy equations. Discretization of the governing equations is achieved using the penalty finite element scheme based on the Galerkin method of weighted residuals.
Findings
The effects of pertinent parameters such as the internal heat generation parameter (Q), the Richardson number (Ri) and the solid volume fraction () on the flow and heat transfer characteristics are presented and discussed. The obtained results depict that the Richardson number plays a significant role on the heat transfer characterization within the triangular wavy chamber. Also, the present results show that an increase in volume fraction has a significant effect on the flow patterns.
Research limitations/implications
Because of the chosen research approach numerically, the research results may lack generalisability. Therefore, researchers are encouraged to test the proposed propositions experimentally.
Practical implications
A nanofluid is a base fluid with suspended metallic nanoparticles. Because traditional fluids used for heat transfer applications such as water, mineral oils and ethylene glycol have a rather low thermal conductivity, nanofluids with relatively higher thermal conductivities have attracted enormous interest from researchers due to their potential in enhancement of heat transfer with little or no penalty in pressure drop.
Originality/value
This paper fulfils an identified need to study how brand-supportive behaviour can be enabled.
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Mahantesh M. Nandeppanavar, T. Srinivasulu and Shanker Bandari
The purpose of this paper is to study the flow, heat and mass transfer of MHD Casson nanofluid due to an inclined stretching sheet using similarity transformation, the governing…
Abstract
Purpose
The purpose of this paper is to study the flow, heat and mass transfer of MHD Casson nanofluid due to an inclined stretching sheet using similarity transformation, the governing PDE’S equations of flow, heat and mass transfer are converted into ODE’S. The resulting non-linear ODE’S are solved numerically using an implicit finite difference method, which is known as Kellor-box method. The effects of various governing parameters on velocity, temperature and concentration are plotted for both Newtonian and non-Newtonian cases. The numerical values of skin friction, Nusselt number and Sherwood number are calculated and tabulated in various tables for different values of physical parameters. It is noticed that the effect of angle of inclination enhances the temperature and concentration profile whereas velocity decreases. The temperature decreases due to the increase in the parametric values of Pr and Gr due to thickening in the boundary layer.
Design/methodology/approach
Numerical method is applied to find the results.
Findings
Flow and heat transfer analysis w.r.t various flow and temperature are analyzed for different values of the physical parameters.
Research limitations/implications
The numerical values of skin friction, Nusselt number and Sherwood number are calculated and tabulated in various tables for different values of physical parameters.
Practical implications
The study of the boundary layer flow, heat and mass transfer is important due to its applications in industries and many manufacturing processes such as aerodynamic extrusion of plastic sheets and cooling of metallic sheets in a cooling bath.
Originality/value
Here in this paper the authors have investigated the MHD boundary layer flow of a Casson nanofluid over an inclined stretching sheet along with the Newtonian nanofluid as a limited.
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Zhe Tian, Ali Abdollahi, Mahmoud Shariati, Atefeh Amindoust, Hossein Arasteh, Arash Karimipour, Marjan Goodarzi and Quang-Vu Bach
This paper aims to study the fluid flow and heat transfer through a spiral double-pipe heat exchanger. Nowadays using spiral double-pipe heat exchangers has become popular in…
Abstract
Purpose
This paper aims to study the fluid flow and heat transfer through a spiral double-pipe heat exchanger. Nowadays using spiral double-pipe heat exchangers has become popular in different industrial segments due to its complex and spiral structure, which causes an enhancement in heat transfer.
Design/methodology/approach
In these heat exchangers, by converting the fluid motion to the secondary motion, the heat transfer coefficient is greater than that of the straight double-pipe heat exchangers and cause increased heat transfer between fluids.
Findings
The present study, by using the Fluent software and nanofluid heat transfer simulation in a spiral double-tube heat exchanger, investigates the effects of operating parameters including fluid inlet velocity, volume fraction of nanoparticles, type of nanoparticles and fluid inlet temperature on heat transfer efficiency.
Originality/value
After presenting the results derived from the fluid numerical simulation and finding the optimal performance conditions using a genetic algorithm, it was found that water–Al2O3 and water–SiO2 nanofluids are the best choices for the Reynolds numbers ranging from 10,551 to 17,220 and 17,220 to 31,910, respectively.
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Farzad Pourfattah, Saeid Yousefi, Omid Ali Akbari, Mahsa Adhampour, Davood Toghraie and Maboud Hekmatifar
The purpose of this paper is to numerically simulate the nanofluid boiling inside a tube in turbulent flow regime and to investigate the effect of adding volume faction of CuO…
Abstract
Purpose
The purpose of this paper is to numerically simulate the nanofluid boiling inside a tube in turbulent flow regime and to investigate the effect of adding volume faction of CuO nanoparticles on the boiling process.
Design/methodology/approach
To make sure the accuracy of the obtained numerical results, the results of this paper have been compared with the experimental results and an acceptable coincidence has been achieved. In the current paper, by Euler–Euler method, the phase change of boiling phenomenon has been modeled. The presented results are the local Nusselt number distribution, temperature distribution of wall, the distribution of volume fraction of vapor phase and fluid temperature at the center of the tube.
Findings
The obtained results indicate that using nanofluid is very effective in the postponement of the boiling process. Hence, by change the amount of volume fraction of nanoparticles in base fluid, the location of phase change and bubble creation are changed. Also, at the Reynolds numbers of 50,000, 100,000 and 150,000 with the volume fraction of 2 per cent, the beginning locations of phase change process are, respectively, 2D, 10D and 13D, and for the volume fraction of 4 per cent, the beginning locations of phase change are 4D, 18D and 19D, respectively. These results indicate that, as the volume fraction of nanoparticles increases, the location of the start of the phase change process is postponed that this issue causes the increment of heat transfer from wall to fluid and the reduction of wall temperature. In general, it can be stated that, in boiling flows, using nanofluid because of the delay in boiling phenomenon has a good effect on heat transfer enhancement of heated walls. Also, the obtained results show that, by increasing Reynolds number, the created vapor phase reduces that leads to increase of the Nusselt number.
Originality/value
The paper investigates the effect of using nanofluid in phase change process of cooling fluid.
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Mokhtar Ferhi and Ridha Djebali
This paper aims to perform the lattice Boltzmann simulation of conjugate natural convection heat transfer, heat flow visualization via heatlines approach and entropy generation in…
Abstract
Purpose
This paper aims to perform the lattice Boltzmann simulation of conjugate natural convection heat transfer, heat flow visualization via heatlines approach and entropy generation in a partitioned medium filled with Ag-MgO (15-85%)/water.
Design/methodology/approach
The lattice Boltzmann method (LBM) is used to predict the dynamic and thermal behaviors. Experimental correlations for dynamic viscosity and thermal conductivity versus solid volume fraction are used. The study is conducted for the ranges of Rayleigh number 103 ≤ Ra ≤ 106, the partitioner thickness 0.01 ≤ δ ≤ 0.9, its position 0.15 ≤ Xs ≤ 0.85 and the hybrid nano-suspensions volume fraction 0% ≤ ϕ ≤ 2%.
Findings
The effects of varying of controlling parameters on the convective flow patterns, temperature contours, heat transfers, the heatlines and the entropy generation are presented. It has been found that the maximum rate of heat transfer enhancement occurs for low Ra numbers (103) and is close to 13.52%. The solid thickness d and its horizontal position Xs have a substantial influence on the heat transfer rate, flow structure, heatline, total entropy generation and Bejan number. Besides, the maximum heat transfer is detected for high Ra and δ ≈ 1 and the percentage of augmentation is equal to 65.55% for ϕ = 2%. According to the horizontal position, the heat transfer remains invariant for Ra = 103 and takes a maximum value near the active walls for Ra ≥ 104. The total entropy generation increases with Ra and decreases with ϕ for Ra = 106. The increase of ϕ from 0 to 2% leads to a reduction in close to 40.76%. For this value of Ra, the entropy is the maximum for δ = 0.4 and Xs = 0.35 and Xs = 0.65%. Moreover, as the Ra increases the Bejan number undergoes a decrease. The Bejan number is the maximum for Ra = 103 independently to δ and Xs. The superior thermal performance manifests at low Ra and high value of δ independently to the positions of the conducting body.
Originality/value
The originality of this paper is to analyze the hybrid nano-additive effects on the two-dimensional conjugate natural convection in a partitioned medium using the LBM. The experimental correlations used for the effective thermal conductivity and dynamic viscosity give credibility to our study. Different approaches such as heatlines and entropy generation are used.
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Amin Shahsavar, Pouyan Talebizadeh Sardari and D. Toghraie
This paper aims to numerically investigate the heat transfer and entropy generation characteristics of water-based hybrid nanofluid in natural convection flow inside a concentric…
Abstract
Purpose
This paper aims to numerically investigate the heat transfer and entropy generation characteristics of water-based hybrid nanofluid in natural convection flow inside a concentric horizontal annulus.
Design/methodology/approach
The hybrid nanofluid is prepared by suspending tetramethylammonium hydroxide-coated Fe3O4 (magnetite) nanoparticles and gum arabic (GA)-coated carbon nanotubes (CNTs) in water. The effects of nanoparticle volume concentration and Rayleigh number on the streamlines, isotherms, average Nusselt number and the thermal, frictional and total entropy generation rates are investigated comprehensively.
Findings
Results show the advantageous effect of hybrid nanofluid on the average Nusselt number. Furthermore, the study of entropy generation shows the increment of both frictional and thermal entropy generation rates by increasing Fe3O4 and CNT concentrations at various Rayleigh numbers. Increasing Rayleigh number from 103 to 105, at Fe3O4 concentration of 0.9 per cent and CNT concentration of 1.35 per cent, increases the average Nusselt number, thermal entropy generation rate and frictional entropy generation rate by 224.95, 224.65 and 155.25 per cent, respectively. Moreover, increasing the Fe3O4 concentration from 0.5 to 0.9 per cent, at Rayleigh number of 105 and CNT concentration of 1.35 per cent, intensifies the average Nusselt number, thermal entropy generation rate and frictional entropy generation rate by 18.36, 22.78 and 72.7 per cent, respectively.
Originality/value
To the best knowledge of the authors, there are not any archival publications considering the detailed behaviour of the natural convective heat transfer and entropy generation of hybrid nanofluid in a concentric annulus.
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Mehdi Bahiraei, Seyed Mostafa Hosseinalipour and Morteza Hangi
The purpose of this paper is to attempt to investigate the particle migration effects on nanofluid heat transfer considering Brownian and thermophoretic forces. It also tries to…
Abstract
Purpose
The purpose of this paper is to attempt to investigate the particle migration effects on nanofluid heat transfer considering Brownian and thermophoretic forces. It also tries to develop a model for prediction of the convective heat transfer coefficient.
Design/methodology/approach
A modified form of the single-phase approach was used in which an equation for mass conservation of particles, proposed by Buongiorno, has been added to the other conservation equations. Due to the importance of temperature in particle migration, temperature-dependent properties were applied. In addition, neural network was used to predict the convective heat transfer coefficient.
Findings
At greater volume fractions, the effect of wall heat flux change was more significant on nanofluid heat transfer coefficient, whereas this effect decreased at higher Reynolds numbers. The average convective heat transfer coefficient raised by increasing the Reynolds number and volume fraction. Considering the particle migration effects, higher heat transfer coefficient was obtained and also the concentration at the tube center was higher in comparison with the wall vicinity. Furthermore, the proposed neural network model predicted the heat transfer coefficient with great accuracy.
Originality/value
A review of the literature shows that in the single-phase approach, uniform concentration distribution has been used and the effects of particle migration have not been considered. In this study, nanofluid heat transfer was simulated by adding an equation to the conservation equations to consider particle migration. The effects of Brownian and thermophoretic forces have been considered in the energy equation. Moreover, a model is proposed for prediction of convective heat transfer coefficient.
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Mahmoud Salari, Emad Hasani Malekshah, Mohammad Reza Sarlak, Masoud Hasani Malekshah and Mohammad Pilfoush
The purpose of this paper is to investigate the three-dimensional natural convection and entropy generation in a cuboid enclosure filled with two immiscible fluids of nanofluid…
Abstract
Purpose
The purpose of this paper is to investigate the three-dimensional natural convection and entropy generation in a cuboid enclosure filled with two immiscible fluids of nanofluid and air.
Design/methodology/approach
One surface of the enclosure is jagged and another one is smooth. The finite volume approach is applied for computation. There are two partially side heaters. Furthermore, the Navier–Stokes equations and entropy generation formulation are solved in the 3D form.
Findings
The effects of different governing parameters, such as the jagged surface (JR=0, 0.02, 0.04, 0.08, 0.12 and 0.16), Rayleigh number (103⩽Ra⩽106) and solid volume fraction of nanofluid (φ=1, 1.5, 2 vol%), on the fluid flow, temperature field, Nusselt number, volumetric entropy generation and Bejan number are presented, comprehensively. The results indicate that the average Nusselt number increases with the increase in the Rayleigh number and solid volume fraction of nanofluid. Moreover, the flow structure is significantly affected by the jagged surface.
Originality/value
The originality of this work is to analyze the natural-convection fluid flow and heat transfer under the influence of jagged surfaces of electrodes in high-current lead–acid batteries.
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Navid Ahmadi Cheloii, Omid Ali Akbari and Davood Toghraie
This study aims to numerically investigate the heat transfer and laminar forced and two-phase flow of Water/Cu nanofluid in a rectangular microchannel with oblique ribs with angle…
Abstract
Purpose
This study aims to numerically investigate the heat transfer and laminar forced and two-phase flow of Water/Cu nanofluid in a rectangular microchannel with oblique ribs with angle of attacks equal to 0-45°. This simulation was conducted in the range of Reynolds numbers of 5-120 in volume fractions of 0, 2 and 4 per cent of solid nanoparticles in three-dimensional space.
Design/methodology/approach
This study investigates the effect of the changes of angle of attack of rectangular rib on heat transfer and hydrodynamics of two-phase flow. This study was done in three-dimensional space and simulation was done with finite volume method. SIMPLEC algorithm and second-order discretization of equations were used to increase the accuracy of results. The usage of nanofluid, application of rips with different angles of attacks and using the two-phase mixture method is the distinction of this paper compared with other studies.
Findings
The results of this research revealed that the changing angle of attack of ribs is an effective factor in heat transfer enhancement. On the other hand, the existence of rib on the internal surfaces of a microchannel increases friction coefficient. By increasing the volume fraction of nanoparticles, due to the augmentation of fluid density and viscosity, the pressure drop increases significantly. For all of the angle of attacks studied in this paper, the maximum rate of performance evaluation criterion has been obtained in Reynolds number of 30 and the minimum amount of performance evaluation criterion was been obtained in Reynolds numbers of 5 and 120.
Originality/value
Many studies have been done in the field of heat transfer in ribbed microchannel. In this paper, the laminar flow in the ribbed microchannel Water/Cu nanofluid in a rectangular microchannel by using two-phase mixture method is numerically investigated with different volume fractions (0-4 per cent), Reynolds numbers (5-120) and angle of attacks of rectangular rib in the indented microchannel (0-45°).
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Vahid Jaferian, Davood Toghraie, Farzad Pourfattah, Omid Ali Akbari and Pouyan Talebizadehsardari
The purpose of this study is three-dimensional flow and heat transfer investigation of water/Al2O3 nanofluid inside a microchannel with different cross-sections in two-phase mode.
Abstract
Purpose
The purpose of this study is three-dimensional flow and heat transfer investigation of water/Al2O3 nanofluid inside a microchannel with different cross-sections in two-phase mode.
Design/methodology/approach
The effect of microchannel walls geometry (trapezoidal, sinusoidal and stepped microchannels) on flow characteristics and also changing circular cross section to trapezoidal cross section in laminar flow at Reynolds numbers of 50, 100, 300 and 600 were investigated. In this study, two-phase water/Al2O3 nanofluid is simulated by the mixture model, and the effect of volume fraction of nanoparticles on performance evaluation criterion (PEC) is studied. The accuracy of obtained results was compared with the experimental and numerical results of other similar papers.
Findings
Results show that in flow at lower Reynolds numbers, sinusoidal walls create a pressure drop in pure water flow which improves heat transfer to obtain PEC < 1. However, in sinusoidal and stepped microchannel with higher Reynolds numbers, PEC > 1. Results showed that the stepped microchannel had higher pressure drop, better thermal performance and higher PEC than other microchannels.
Originality/value
Review of previous studies showed that existing papers have not compared and investigated nanofluid in a two-phase mode in inhomogeneous circular, stepped and sinusoidal cross and trapezoidal cross-sections by considering the effect of changing channel shape, which is the aim of the present paper.
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