This article presents a numerical investigation of heat transfer performance and pressure drop of nanofluids flowing under laminar flow conditions. Various nanoparticles including Al2O3, CuO, carbon nanotube and titanate nanotube dispersed in water and ethylene glycol/water were simulated. A single-phase model was used to predict the effects of parameters such as particle concentration, diameter, Brownian motion, Reynolds number, nanoparticle type and base fluid on heat transfer coefficient and pressure drop. The results indicated that particle concentration, Brownian motion and aspect ratio increased heat transfer, while particle diameter decreased it. The study provides considerations for choosing appropriate nanofluids for applications.
Study on Thermal and Hydrodynamic Indexes of a Nanofluid Flow in a Micro Heat...A Behzadmehr
The paper numerically presents laminar forced convection of a nanofluid flowing in a duct at microscale.
Results were compared with both analytical and experimental data and observed good concordance with
previous studies available in the literature. Influences of Brinkman and Reynolds number on thermal and
hydrodynamic indexes have been investigated. For a given nanofluid, no change in efficiency (heat dissipation
to pumping power) was observed with an increasing in Reynolds number. It was shown that the pressure was
decrease with an increase in Brinkman number. Dependency of Nu increment changes with substrate material.
MHD Chemically Reacting and Radiating Nanofluid Flow over a Vertical Cone Emb...IJLT EMAS
In this study, we examine the combined effects of
thermal radiation, chemical reaction on MHD hydromagnetic
boundary layer flow over a vertical cone filled with nanofluid
saturated porous medium under variable properties. The
governing flow, heat and mass transfer equations are
transformed into ordinary differential equations using similarity
variables and are solved numerically by a Galerkin Finite
element method. Numerical results are obtained for
dimensionless velocity, temperature, nanoparticle volume
fraction, as well as the skin friction, local Nusselt and Sherwood
number for the different values of the pertinent parameters
entered into the problem. The effects of various controlling
parameters on these quantities are investigated. Pertinent
results are presented graphically and discussed quantitatively.
The present results are compared with existing results and found
to be good agreement. It is found that the temperature of the
fluid remarkably enhances with the rising values of Brownian
motion parameter (Nb).
This document summarizes a research article that analyzes the stability of a horizontal porous layer saturated with a viscoelastic nanofluid when the boundaries are subjected to periodic temperature modulation. The analysis uses the Darcy-Brinkman-Oldroyd-B fluid model and considers infinitesimal disturbances. Three cases of oscillatory temperature fields are examined: symmetric modulation, asymmetric modulation, and modulation of only the bottom wall. A perturbation solution is obtained and the effect of modulation frequency on stability is shown. The stability is characterized by a correction Rayleigh number calculated as a function of various parameters representing viscoelasticity, concentration, porosity, heat capacity, and modulation frequency. Modulation is found to generally have a destabilizing
iaetsd Nanofluid heat transfer a reviewIaetsd Iaetsd
This document summarizes research on using nanofluids to enhance heat transfer. Nanofluids are fluids containing nanosized particles that can increase the thermal conductivity of the base fluid. Several studies have found that nanofluids can increase heat transfer rates compared to the base fluid alone. The amount of heat transfer enhancement depends on factors like the nanoparticle material, size, concentration, and whether the fluid flow is laminar or turbulent. Nanofluids show potential for applications like cooling engines, electronics, and nuclear systems. However, issues like long-term stability, increased pumping power needs, and high production costs still need to be addressed for more widespread use of nanofluids in industries.
Experimental Study on the Effect of CuO DI Water Nanofluids on Heat Transfer ...YogeshIJTSRD
The document summarizes an experimental study on the heat transfer and pressure drop characteristics of CuO/DI water nanofluids flowing through a plain tube with spiraled rod inserts (SRI) under laminar flow conditions. Key findings include a 19% increase in Nusselt number for nanofluids compared to DI water in a plain tube, and increases of 35.9% and 37.2% with nanofluids and 50mm and 30mm pitches SRI respectively. The estimated friction factor with nanofluids was 4.2% higher than DI water, considered insignificant. Previous studies finding heat transfer enhancement of nanofluids are also summarized.
IRJET- Numerical Analysis of Natural Convection of Nano Fluids on Square ...IRJET Journal
This document summarizes a numerical analysis of natural convection of nanofluids in square enclosures. Aluminum oxide and titanium oxide nanoparticles dispersed in water were analyzed at low concentrations from 0.1-0.4% and Rayleigh numbers from 2x10^7 to 8x10^7. The study found that aluminum oxide provided up to 33% enhancement in heat transfer properties over the base fluid, while titanium oxide provided up to 22% enhancement. Both nanofluids showed increased heat transfer with higher Rayleigh numbers but decreased transfer with higher concentrations. The analysis was conducted using ANSYS Fluent software to solve governing equations for the 3D, steady flow using the SIMPLE pressure-linking scheme.
Experimental investigation on thermo physical properties of single walled car...Sabiha Akter Monny
This document experimentally investigates the thermo physical properties of single walled carbon nanotube (SWCNT) nanofluids. Stable SWCNT nanofluids were prepared with concentrations of 0.05-0.25% volume using sodium dodecyl sulfate as a surfactant. Thermal conductivity was measured to increase from 0.615-0.892 W/m K, viscosity increased from 0.67-1.28 mPa s, and specific heat increased from 2.97-3.90 kJ/kg °C as temperature and concentration increased. The maximum 36.39% enhancement in thermal conductivity over water was observed at 0.25% concentration and 60°C. Viscosity exhibited
Welcome to International Journal of Engineering Research and Development (IJERD)IJERD Editor
journal publishing, how to publish research paper, Call For research paper, international journal, publishing a paper, IJERD, journal of science and technology, how to get a research paper published, publishing a paper, publishing of journal, publishing of research paper, reserach and review articles, IJERD Journal, How to publish your research paper, publish research paper, open access engineering journal, Engineering journal, Mathemetics journal, Physics journal, Chemistry journal, Computer Engineering, Computer Science journal, how to submit your paper, peer reviw journal, indexed journal, reserach and review articles, engineering journal, www.ijerd.com, research journals,
yahoo journals, bing journals, International Journal of Engineering Research and Development, google journals, hard copy of journal
Study on Thermal and Hydrodynamic Indexes of a Nanofluid Flow in a Micro Heat...A Behzadmehr
The paper numerically presents laminar forced convection of a nanofluid flowing in a duct at microscale.
Results were compared with both analytical and experimental data and observed good concordance with
previous studies available in the literature. Influences of Brinkman and Reynolds number on thermal and
hydrodynamic indexes have been investigated. For a given nanofluid, no change in efficiency (heat dissipation
to pumping power) was observed with an increasing in Reynolds number. It was shown that the pressure was
decrease with an increase in Brinkman number. Dependency of Nu increment changes with substrate material.
MHD Chemically Reacting and Radiating Nanofluid Flow over a Vertical Cone Emb...IJLT EMAS
In this study, we examine the combined effects of
thermal radiation, chemical reaction on MHD hydromagnetic
boundary layer flow over a vertical cone filled with nanofluid
saturated porous medium under variable properties. The
governing flow, heat and mass transfer equations are
transformed into ordinary differential equations using similarity
variables and are solved numerically by a Galerkin Finite
element method. Numerical results are obtained for
dimensionless velocity, temperature, nanoparticle volume
fraction, as well as the skin friction, local Nusselt and Sherwood
number for the different values of the pertinent parameters
entered into the problem. The effects of various controlling
parameters on these quantities are investigated. Pertinent
results are presented graphically and discussed quantitatively.
The present results are compared with existing results and found
to be good agreement. It is found that the temperature of the
fluid remarkably enhances with the rising values of Brownian
motion parameter (Nb).
This document summarizes a research article that analyzes the stability of a horizontal porous layer saturated with a viscoelastic nanofluid when the boundaries are subjected to periodic temperature modulation. The analysis uses the Darcy-Brinkman-Oldroyd-B fluid model and considers infinitesimal disturbances. Three cases of oscillatory temperature fields are examined: symmetric modulation, asymmetric modulation, and modulation of only the bottom wall. A perturbation solution is obtained and the effect of modulation frequency on stability is shown. The stability is characterized by a correction Rayleigh number calculated as a function of various parameters representing viscoelasticity, concentration, porosity, heat capacity, and modulation frequency. Modulation is found to generally have a destabilizing
iaetsd Nanofluid heat transfer a reviewIaetsd Iaetsd
This document summarizes research on using nanofluids to enhance heat transfer. Nanofluids are fluids containing nanosized particles that can increase the thermal conductivity of the base fluid. Several studies have found that nanofluids can increase heat transfer rates compared to the base fluid alone. The amount of heat transfer enhancement depends on factors like the nanoparticle material, size, concentration, and whether the fluid flow is laminar or turbulent. Nanofluids show potential for applications like cooling engines, electronics, and nuclear systems. However, issues like long-term stability, increased pumping power needs, and high production costs still need to be addressed for more widespread use of nanofluids in industries.
Experimental Study on the Effect of CuO DI Water Nanofluids on Heat Transfer ...YogeshIJTSRD
The document summarizes an experimental study on the heat transfer and pressure drop characteristics of CuO/DI water nanofluids flowing through a plain tube with spiraled rod inserts (SRI) under laminar flow conditions. Key findings include a 19% increase in Nusselt number for nanofluids compared to DI water in a plain tube, and increases of 35.9% and 37.2% with nanofluids and 50mm and 30mm pitches SRI respectively. The estimated friction factor with nanofluids was 4.2% higher than DI water, considered insignificant. Previous studies finding heat transfer enhancement of nanofluids are also summarized.
IRJET- Numerical Analysis of Natural Convection of Nano Fluids on Square ...IRJET Journal
This document summarizes a numerical analysis of natural convection of nanofluids in square enclosures. Aluminum oxide and titanium oxide nanoparticles dispersed in water were analyzed at low concentrations from 0.1-0.4% and Rayleigh numbers from 2x10^7 to 8x10^7. The study found that aluminum oxide provided up to 33% enhancement in heat transfer properties over the base fluid, while titanium oxide provided up to 22% enhancement. Both nanofluids showed increased heat transfer with higher Rayleigh numbers but decreased transfer with higher concentrations. The analysis was conducted using ANSYS Fluent software to solve governing equations for the 3D, steady flow using the SIMPLE pressure-linking scheme.
Experimental investigation on thermo physical properties of single walled car...Sabiha Akter Monny
This document experimentally investigates the thermo physical properties of single walled carbon nanotube (SWCNT) nanofluids. Stable SWCNT nanofluids were prepared with concentrations of 0.05-0.25% volume using sodium dodecyl sulfate as a surfactant. Thermal conductivity was measured to increase from 0.615-0.892 W/m K, viscosity increased from 0.67-1.28 mPa s, and specific heat increased from 2.97-3.90 kJ/kg °C as temperature and concentration increased. The maximum 36.39% enhancement in thermal conductivity over water was observed at 0.25% concentration and 60°C. Viscosity exhibited
Welcome to International Journal of Engineering Research and Development (IJERD)IJERD Editor
journal publishing, how to publish research paper, Call For research paper, international journal, publishing a paper, IJERD, journal of science and technology, how to get a research paper published, publishing a paper, publishing of journal, publishing of research paper, reserach and review articles, IJERD Journal, How to publish your research paper, publish research paper, open access engineering journal, Engineering journal, Mathemetics journal, Physics journal, Chemistry journal, Computer Engineering, Computer Science journal, how to submit your paper, peer reviw journal, indexed journal, reserach and review articles, engineering journal, www.ijerd.com, research journals,
yahoo journals, bing journals, International Journal of Engineering Research and Development, google journals, hard copy of journal
EXPERIMENTAL INVESTIGATION ON IMPROVING THE COOLING PERFORMANCE OF AUTOMOBILE...IAEME Publication
The convective heat transfer rate inside a flat tube radiator of an automobile using
CuO-Water nanofluids were investigated experimentally and numerically. Nanofluid
of 0.1%, 0.2%, 0.3% volume concentrations were prepared using CuO nanoparticle
with water as base fluid. The effect of mass flow rate, volume concentration inlet
temperature on heat transfer rate with varied coolant mass flow rate ranging from
6LPM, 8LPM, 10LPM were examined. Results shows that heat transfer rate linearly
increases with increase in mass flow rate and volume concentration, the best heat
transfer rate is achieved at 0.3% volume fraction of CuO at 10LPM. A maximum
enhancement of 35% in heat transfer rate is obtained for 0.3% concentration of CuO
nanofluid
This study measured the thermal conductivity and viscosity of TiO2 nanoparticles dispersed in deionized water at concentrations up to 3% volume fraction and temperatures from 13°C to 55°C. Thermal conductivity was measured using the 3ω method, which was validated on pure fluids. Results showed thermal conductivity increased with particle concentration but not anomalously, and was not strongly temperature dependent. Viscosity significantly increased with particle concentration beyond classical models, and decreased exponentially with temperature like the base fluid. Increasing temperature and particle concentration both increased heat transfer properties, with viscosity enhanced more than thermal conductivity.
Investigation of the Effect of Nanoparticles Mean Diameter on Turbulent Mixed...A Behzadmehr
Abstract
Turbulent mixed convection of a nanofluid (water/Al2O3, Φ=.02) has been studied numerically. Two-phase
mixture model has been used to investigate the effects of nanoparticles mean diameter on the flow parameters. Nanoparticles distribution at the tube cross section shows that the particles are uniformly dispersed. The non-uniformity of the particles distribution occurs in the case of large nanoparticles and/or high value of the Grashof numbers. The study of particle size effect showed that the effective Nusselt number and turbulent intensity increases with the decreased of particle size.
The Force Convection Heat Transfer of A Nanofluid Over A Flat Plate: Using Th...AEIJjournal2
A drift-flux model is utilized to theoretically analyze the boundary layer flow and heat transfer of a
nanofluid over a flat plate. The concentration of nanoparticles at the plate is obtained using the solution of
the governing equations. Assuming a fixed magnitude of free stream velocity, the results show that the heat
transfer may enhance up to 22% or decrease about -7% by using nanofluids compared to the pure base
fluid.
An Investigation of effect of Temperature Difference and Initial Moisture Con...ijsrd.com
The study of natural convection involves analysis of surface geometry that is having fluid- saturated porous medium. Various temperature differences are considered between the two isolated walls, while the top wall considered being an adiabatic. CFD tool and mathematical analysis was studied and analyzed to carry out the research. By the help of study, it is analyzed that higher intensity rate of natural convection. The simulation of the various temperatures and initial moisture contents were carried out to determine the effect on the performance of the natural convection. It has been noticed that temperature over the porous medium is uniformly distributed due to conduction, which is little higher in the fluid region. It has been recorded that the high moisture contents at the higher temperature side wall than lower one.
NUMERICAL INVESTIGATION OF NATURAL CONVECTION HEAT TRANSFER FROM CIRCULAR CYL...IAEME Publication
In the present work, the enhancement of natural convection heat transfer utilizing nanofluids as working fluid from horizontal circular cylinder situated in a square enclosure is investigated numerically. The type of the nanofluid is the water-based copper Cu. A model is developed to analyze heat transfer performance of nanofluids inside an enclosure taking into account the solid particle dispersionrs on the flow and heat transfer characteristics. The study uses different Raylieh
numbers (104 , 105 , and 106 ), different enclosure width to cylinder diameter ratios W/D (1.667, 2.5 and 5) and volume fraction of nanoparticles between 0 to 0.2. The work included the solution of the governing equations in the vorticity-stream function formulation which were transformed into body fitted coordinate system
To study the behavior of nanofluids in heat transfer applications a revieweSAT Journals
Abstract Using nanofluids as an innovative kind of liquid blend including trivial volume fraction (in percent) of millimeter or nanometer size powdered particles with base fluids is fairly a novel arena or idea. The objective of this presented review paper is to inspect the performance of the nanofluid-based solar collector (NBSC). In past few years for a number of experimental and industrial thermal engineering systems solar energy has proven to be the best input energy source. Nanofluids are the fluid that has shown various developments in the thermal properties over the past decade. In the field of nanotechnology, nano fluids have a great potential to enhance the rheological properties like thermal conductivity of base fluid like water, ethanol etc. Nanofluids are the suspension of mainly the base fluid like water in nanoparticles such as alumina (Al2O3) of size micro or milimetre and shows distinctive features than that of conservative fluids used. Because of better rheological properties nanofluids are utilized to build up the performance of conventional solar thermal engineering systems. The presented literature review presents a detailed discussion about the solar collectors, applications of nanofluids in solar collector and their augmentation in thermo physical properties. Keywords: Nano fluids, Nanoparticles, Solar collector, Thermal conductivity
Surface tension of Nanofluid-type fuels containing suspended nanomaterialsSaad Tanvir
The surface tension of ethanol and n-decane based nanofluid fuels containing suspended aluminum, aluminum oxide, boron nanoparticles, and carbon nanotubes was measured. The results showed that surface tension generally increases with higher nanoparticle concentration and larger particle size due to increased van der Waals forces at the liquid-gas interface. However, when a surfactant was used or with carbon nanotubes, surface tension decreased compared to the base fluid, possibly due to increased electrostatic forces between particles. There are contradictory conclusions in previous literature on how nanoparticle addition affects surface tension, which motivated this study to provide more clarity.
This document summarizes a study that investigated heat transfer in a plate heat exchanger using water-based TiO2 nanofluids. Two different weight fractions (0.1% and 0.5%) of TiO2 nanofluids were prepared and their heat transfer performance was experimentally tested in the plate heat exchanger. The results showed that the 0.5% nanofluid provided significant enhancement of the overall heat transfer coefficient at higher Reynolds numbers compared to water, while the 0.1% nanofluid showed a decrease compared to water.
Penga Ž, Tolj I, Barbir F, Computational fluid dynamics study of PEM fuel cel...Željko Penga
This computational fluid dynamics study examines PEM fuel cell performance under isothermal and non-uniform temperature boundary conditions. The study finds that implementing a non-uniform temperature profile along the cathode channel, as calculated from a Mollier h-u chart, results in close to 100% relative humidity without external humidification and improves fuel cell performance. The model polarization curve and relative humidity distribution agree well with experimental results. Different current collector materials and membrane thickness influence temperature and relative humidity distributions through their effects on thermal conductivity and water transport.
Numerical simulation and enhancement of heat transfer using cuo water nano fl...IAEME Publication
This document summarizes a study on enhancing heat transfer using CuO/water nanofluid and a twisted tape insert with alternate axis in a circular tube. Numerical simulations were performed using ANSYS FLUENT to analyze heat transfer, friction, and thermal performance of the nanofluid at various concentrations from 0.3-0.7% by volume. The simulations also examined using nanofluid with a typical twisted tape, the twisted tape alone, and nanofluid alone. Results showed that using nanofluid together with the twisted tape with alternate axis can further improve heat transfer compared to using them individually.
Moving Lids Direction Effects on MHD Mixed Convection in a Two-Sided Lid-Driv...A Behzadmehr
Magnetohydrodynamic (MHD) mixed convection flow of Cu–water nanofluid inside a two-sided lid-driven square enclosure with adiabatic horizontal walls and differentially heated sidewalls has been investigated numerically. The effects of moving lids direction, variations of Richardson number, Hartmann number, and volume fraction of nanoparticles on flow and temperature fields have been studied. The obtained results show that for a constant Grashof number (), the rate of heat transfer increases with a decrease in the Richardson and Hartmann numbers. Furthermore, an increase of the volume fraction of nanoparticles may result in enhancement or deterioration of the heat transfer performance depending on the value of the Hartmann and Richardson numbers and the configuration of the moving lids. Also, it is found that in the presence of magnetic field, the nanoparticles have their maximum positive effect when the top lid moves rightward and the bottom one moves leftward.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
IRJET- Review on Applications of Metal and Metal Oxide Nanoparticle in Heat a...IRJET Journal
This document reviews applications of metal and metal oxide nanoparticles in heat and mass transfer studies. It summarizes various literature that has investigated using nanoparticles suspended in base fluids. The literature shows that nanoparticles can improve the thermal conductivity and heat transfer rate of base fluids. Nanoparticles like Al2O3, CuO, ZnO, TiO2 suspended in fluids like water and ethylene glycol have demonstrated enhanced heat transfer in applications like heat exchangers and cooling systems. Some literature also found improved mass transfer and absorption rates for processes like CO2 absorption when using nanoparticle suspensions. In general, the reviewed works indicate nanoparticles have potential to improve heat and mass transfer properties and rates compared to conventional fluids without nanoparticles.
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology
Experimental investigation of cooling performance of an Automobile radiator u...IJERD Editor
This document summarizes an experimental study that investigated the cooling performance of an automobile radiator using an Al2O3-water+ethylene glycol nanofluid. Different volume fractions of Al2O3 nanoparticles between 0.01-0.08% were added to the base fluid and tested. The maximum heat transfer performance observed was a 48% increase over water for the 0.08% volume fraction nanofluid. Flow rates were also varied between 3-15 liters per minute, showing increased heat transfer with higher flow. The nanofluid had increased thermal conductivity compared to the base fluid, improving the radiator's cooling capacity.
Improving the Cooling Performance of Automobile Radiator with Ethylene Glycol...IRJET Journal
This document summarizes research on improving the cooling performance of an automobile radiator using ethylene glycol-water based ZrO2 and Al2O3 nanofluids. Key findings include:
1) Experiments were conducted using different volume concentrations of ZrO2 and Al2O3 nanofluids at varying flow rates and a constant inlet temperature of 90°C.
2) Results showed that heat transfer coefficients and Nusselt numbers increased with higher nanoparticle concentrations and flow rates for both nanofluids. ZrO2 nanofluid performed better than Al2O3 nanofluid.
3) Outlet temperatures of the radiator decreased more when using nanofluids compared to the
Improving the Cooling Performance of Automobile Radiator with TiO2/Water Nano...ijsrd.com
In this paper, forced convective heat transfer in a water based nanofluid has experimentally beencompared to that of pure water in an automobile radiator. Five different concentrations of nanofluids inthe range of 0.1-1 vol.% have been prepared by the addition of TiO2 nanoparticles into the water. The test liquid flows through the radiator consisted of 34 vertical tubes with elliptical cross section and airmakes a cross flow inside the tube bank with constant speed. Liquid flow rate has been changed in therange of 90-120 l/min to have the fully turbulent regime. Results demonstrate that increasing the fluid circulating rate canimprove the heat transfer performance. Meanwhile, application of nanofluid with low concentrations can enhance heat transfer efficiency up to 45% in comparison with pure water.
EXPERIMENTAL INVESTIGATION ON IMPROVING THE COOLING PERFORMANCE OF AUTOMOBILE...IAEME Publication
The convective heat transfer rate inside a flat tube radiator of an automobile using
CuO-Water nanofluids were investigated experimentally and numerically. Nanofluid
of 0.1%, 0.2%, 0.3% volume concentrations were prepared using CuO nanoparticle
with water as base fluid. The effect of mass flow rate, volume concentration inlet
temperature on heat transfer rate with varied coolant mass flow rate ranging from
6LPM, 8LPM, 10LPM were examined. Results shows that heat transfer rate linearly
increases with increase in mass flow rate and volume concentration, the best heat
transfer rate is achieved at 0.3% volume fraction of CuO at 10LPM. A maximum
enhancement of 35% in heat transfer rate is obtained for 0.3% concentration of CuO
nanofluid
This study measured the thermal conductivity and viscosity of TiO2 nanoparticles dispersed in deionized water at concentrations up to 3% volume fraction and temperatures from 13°C to 55°C. Thermal conductivity was measured using the 3ω method, which was validated on pure fluids. Results showed thermal conductivity increased with particle concentration but not anomalously, and was not strongly temperature dependent. Viscosity significantly increased with particle concentration beyond classical models, and decreased exponentially with temperature like the base fluid. Increasing temperature and particle concentration both increased heat transfer properties, with viscosity enhanced more than thermal conductivity.
Investigation of the Effect of Nanoparticles Mean Diameter on Turbulent Mixed...A Behzadmehr
Abstract
Turbulent mixed convection of a nanofluid (water/Al2O3, Φ=.02) has been studied numerically. Two-phase
mixture model has been used to investigate the effects of nanoparticles mean diameter on the flow parameters. Nanoparticles distribution at the tube cross section shows that the particles are uniformly dispersed. The non-uniformity of the particles distribution occurs in the case of large nanoparticles and/or high value of the Grashof numbers. The study of particle size effect showed that the effective Nusselt number and turbulent intensity increases with the decreased of particle size.
The Force Convection Heat Transfer of A Nanofluid Over A Flat Plate: Using Th...AEIJjournal2
A drift-flux model is utilized to theoretically analyze the boundary layer flow and heat transfer of a
nanofluid over a flat plate. The concentration of nanoparticles at the plate is obtained using the solution of
the governing equations. Assuming a fixed magnitude of free stream velocity, the results show that the heat
transfer may enhance up to 22% or decrease about -7% by using nanofluids compared to the pure base
fluid.
An Investigation of effect of Temperature Difference and Initial Moisture Con...ijsrd.com
The study of natural convection involves analysis of surface geometry that is having fluid- saturated porous medium. Various temperature differences are considered between the two isolated walls, while the top wall considered being an adiabatic. CFD tool and mathematical analysis was studied and analyzed to carry out the research. By the help of study, it is analyzed that higher intensity rate of natural convection. The simulation of the various temperatures and initial moisture contents were carried out to determine the effect on the performance of the natural convection. It has been noticed that temperature over the porous medium is uniformly distributed due to conduction, which is little higher in the fluid region. It has been recorded that the high moisture contents at the higher temperature side wall than lower one.
NUMERICAL INVESTIGATION OF NATURAL CONVECTION HEAT TRANSFER FROM CIRCULAR CYL...IAEME Publication
In the present work, the enhancement of natural convection heat transfer utilizing nanofluids as working fluid from horizontal circular cylinder situated in a square enclosure is investigated numerically. The type of the nanofluid is the water-based copper Cu. A model is developed to analyze heat transfer performance of nanofluids inside an enclosure taking into account the solid particle dispersionrs on the flow and heat transfer characteristics. The study uses different Raylieh
numbers (104 , 105 , and 106 ), different enclosure width to cylinder diameter ratios W/D (1.667, 2.5 and 5) and volume fraction of nanoparticles between 0 to 0.2. The work included the solution of the governing equations in the vorticity-stream function formulation which were transformed into body fitted coordinate system
To study the behavior of nanofluids in heat transfer applications a revieweSAT Journals
Abstract Using nanofluids as an innovative kind of liquid blend including trivial volume fraction (in percent) of millimeter or nanometer size powdered particles with base fluids is fairly a novel arena or idea. The objective of this presented review paper is to inspect the performance of the nanofluid-based solar collector (NBSC). In past few years for a number of experimental and industrial thermal engineering systems solar energy has proven to be the best input energy source. Nanofluids are the fluid that has shown various developments in the thermal properties over the past decade. In the field of nanotechnology, nano fluids have a great potential to enhance the rheological properties like thermal conductivity of base fluid like water, ethanol etc. Nanofluids are the suspension of mainly the base fluid like water in nanoparticles such as alumina (Al2O3) of size micro or milimetre and shows distinctive features than that of conservative fluids used. Because of better rheological properties nanofluids are utilized to build up the performance of conventional solar thermal engineering systems. The presented literature review presents a detailed discussion about the solar collectors, applications of nanofluids in solar collector and their augmentation in thermo physical properties. Keywords: Nano fluids, Nanoparticles, Solar collector, Thermal conductivity
Surface tension of Nanofluid-type fuels containing suspended nanomaterialsSaad Tanvir
The surface tension of ethanol and n-decane based nanofluid fuels containing suspended aluminum, aluminum oxide, boron nanoparticles, and carbon nanotubes was measured. The results showed that surface tension generally increases with higher nanoparticle concentration and larger particle size due to increased van der Waals forces at the liquid-gas interface. However, when a surfactant was used or with carbon nanotubes, surface tension decreased compared to the base fluid, possibly due to increased electrostatic forces between particles. There are contradictory conclusions in previous literature on how nanoparticle addition affects surface tension, which motivated this study to provide more clarity.
This document summarizes a study that investigated heat transfer in a plate heat exchanger using water-based TiO2 nanofluids. Two different weight fractions (0.1% and 0.5%) of TiO2 nanofluids were prepared and their heat transfer performance was experimentally tested in the plate heat exchanger. The results showed that the 0.5% nanofluid provided significant enhancement of the overall heat transfer coefficient at higher Reynolds numbers compared to water, while the 0.1% nanofluid showed a decrease compared to water.
Penga Ž, Tolj I, Barbir F, Computational fluid dynamics study of PEM fuel cel...Željko Penga
This computational fluid dynamics study examines PEM fuel cell performance under isothermal and non-uniform temperature boundary conditions. The study finds that implementing a non-uniform temperature profile along the cathode channel, as calculated from a Mollier h-u chart, results in close to 100% relative humidity without external humidification and improves fuel cell performance. The model polarization curve and relative humidity distribution agree well with experimental results. Different current collector materials and membrane thickness influence temperature and relative humidity distributions through their effects on thermal conductivity and water transport.
Numerical simulation and enhancement of heat transfer using cuo water nano fl...IAEME Publication
This document summarizes a study on enhancing heat transfer using CuO/water nanofluid and a twisted tape insert with alternate axis in a circular tube. Numerical simulations were performed using ANSYS FLUENT to analyze heat transfer, friction, and thermal performance of the nanofluid at various concentrations from 0.3-0.7% by volume. The simulations also examined using nanofluid with a typical twisted tape, the twisted tape alone, and nanofluid alone. Results showed that using nanofluid together with the twisted tape with alternate axis can further improve heat transfer compared to using them individually.
Moving Lids Direction Effects on MHD Mixed Convection in a Two-Sided Lid-Driv...A Behzadmehr
Magnetohydrodynamic (MHD) mixed convection flow of Cu–water nanofluid inside a two-sided lid-driven square enclosure with adiabatic horizontal walls and differentially heated sidewalls has been investigated numerically. The effects of moving lids direction, variations of Richardson number, Hartmann number, and volume fraction of nanoparticles on flow and temperature fields have been studied. The obtained results show that for a constant Grashof number (), the rate of heat transfer increases with a decrease in the Richardson and Hartmann numbers. Furthermore, an increase of the volume fraction of nanoparticles may result in enhancement or deterioration of the heat transfer performance depending on the value of the Hartmann and Richardson numbers and the configuration of the moving lids. Also, it is found that in the presence of magnetic field, the nanoparticles have their maximum positive effect when the top lid moves rightward and the bottom one moves leftward.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
IRJET- Review on Applications of Metal and Metal Oxide Nanoparticle in Heat a...IRJET Journal
This document reviews applications of metal and metal oxide nanoparticles in heat and mass transfer studies. It summarizes various literature that has investigated using nanoparticles suspended in base fluids. The literature shows that nanoparticles can improve the thermal conductivity and heat transfer rate of base fluids. Nanoparticles like Al2O3, CuO, ZnO, TiO2 suspended in fluids like water and ethylene glycol have demonstrated enhanced heat transfer in applications like heat exchangers and cooling systems. Some literature also found improved mass transfer and absorption rates for processes like CO2 absorption when using nanoparticle suspensions. In general, the reviewed works indicate nanoparticles have potential to improve heat and mass transfer properties and rates compared to conventional fluids without nanoparticles.
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology
Experimental investigation of cooling performance of an Automobile radiator u...IJERD Editor
This document summarizes an experimental study that investigated the cooling performance of an automobile radiator using an Al2O3-water+ethylene glycol nanofluid. Different volume fractions of Al2O3 nanoparticles between 0.01-0.08% were added to the base fluid and tested. The maximum heat transfer performance observed was a 48% increase over water for the 0.08% volume fraction nanofluid. Flow rates were also varied between 3-15 liters per minute, showing increased heat transfer with higher flow. The nanofluid had increased thermal conductivity compared to the base fluid, improving the radiator's cooling capacity.
Improving the Cooling Performance of Automobile Radiator with Ethylene Glycol...IRJET Journal
This document summarizes research on improving the cooling performance of an automobile radiator using ethylene glycol-water based ZrO2 and Al2O3 nanofluids. Key findings include:
1) Experiments were conducted using different volume concentrations of ZrO2 and Al2O3 nanofluids at varying flow rates and a constant inlet temperature of 90°C.
2) Results showed that heat transfer coefficients and Nusselt numbers increased with higher nanoparticle concentrations and flow rates for both nanofluids. ZrO2 nanofluid performed better than Al2O3 nanofluid.
3) Outlet temperatures of the radiator decreased more when using nanofluids compared to the
Improving the Cooling Performance of Automobile Radiator with TiO2/Water Nano...ijsrd.com
In this paper, forced convective heat transfer in a water based nanofluid has experimentally beencompared to that of pure water in an automobile radiator. Five different concentrations of nanofluids inthe range of 0.1-1 vol.% have been prepared by the addition of TiO2 nanoparticles into the water. The test liquid flows through the radiator consisted of 34 vertical tubes with elliptical cross section and airmakes a cross flow inside the tube bank with constant speed. Liquid flow rate has been changed in therange of 90-120 l/min to have the fully turbulent regime. Results demonstrate that increasing the fluid circulating rate canimprove the heat transfer performance. Meanwhile, application of nanofluid with low concentrations can enhance heat transfer efficiency up to 45% in comparison with pure water.
Celas Maya is a language school located in Quetzaltenango, Guatemala that offers Spanish and K'iche language classes. It provides one-on-one and small group classes, as well as opportunities for volunteer work and internships. The school aims to create a high-quality immersion experience for students through its various programs and services.
This document summarizes a presentation about Universal Design for Learning (UDL). It discusses how UDL and technology can provide accommodations to help diverse learners access curriculum. UDL aims to reduce barriers in education by providing multiple means of representation, engagement, and action/expression. It also notes that UDL supports diversity through flexibility in learning, assessments, and engagement of recognition, strategic and affective networks as revealed by brain research. Resources for implementing UDL like online tools are provided.
Šta sve ugrožava opstanak životinja i dovodi do smanjenja brojnosti njihovih populacija ili do izumiranja vrste. Koje su ugrožene vrste na području Srbije, a koje su globalno ugrožene, kako ih zaštititi i omogućiti im opstanak.
Ms. Apple Guanzon
Group Leader: Mark Lloyd Coloma
Members:
Dallin Villa
Sheila Mae Ruth Cagadas
Analyn Dejaro
Jane Katherine Tobis
Nerise Jean Voluntate
Teacher: Mr. Ursecio “Urs” Inodeo
1. article in mathematical problems in engineering 2020MohamedSANNAD2
This document summarizes a numerical study that simulated natural convection heat transfer in a cubical cavity filled with nanofluids. The cavity is heated by a partition maintained at a hot temperature, while the right and left walls are kept at a cold temperature and the rest are adiabatic. Results show that increasing the Rayleigh number, volume fraction of nanoparticles, and size of the heating partition all improve heat transfer. Copper-based nanofluids provided the best thermal transfer. The study analyzes temperature, velocity and heat transfer to understand how nanofluids affect natural convection in 3D enclosures.
Evaluation of Shell and Tube Heat Exchanger Performance by Using ZnO/Water Na...Barhm Mohamad
To examine and investigate the impact of nanofluid on heat exchanger performance, including the total heat transfer, the effect of friction factor, the average Nusselt number, and the thermal efficiency, the output heat transfers of a shell and tube heat exchanger using ZnO nanoparticles suspended in water has been conducted numerically. The governing equations were solved using finite volume techniques and CFD simulations with ANSYS/FLUENT Solver 2021. The nanoparticles volume fractions adopted are 0.2% and 0.35% that used in numerical computations under 200 to 1400 Reynolds numbers range. The increasing of temperature is approximately 13% from the bottom to the top of heat exchanger, while the maximum enhancement of Nusselt number is about 10%, 19% for volume fractions 0.2% and 0.35% respectively. The elevated values of the friction factor at the volumetric ratios of 0.2% and 0.35% are 0.25% and 0.47% respectively. The findings demonstrate that the performance efficiency of shell and tube heat exchanger is enhanced due to the increase in Nusselt number.
This document reviews the preparation, properties, and applications of nanofluids. It discusses:
1) Methods for preparing nanofluids and factors that influence their stability and thermal properties.
2) Experimental and theoretical models that have been used to analyze the thermal conductivity and other properties of nanofluids. Many studies found thermal conductivity increased significantly with only small amounts of nanoparticles.
3) Potential applications of nanofluids in various industries where enhanced heat transfer is important, such as electronics, automobiles, and power plants. However, issues around nanofluid stability and production costs need further research before wide commercial use.
The Force Convection Heat Transfer of A Nanofluid Over A Flat Plate: Using Th...AEIJjournal2
Advanced Energy: An International Journal (AEIJ) is a quarterly open access peer-reviewed journal that publishes articles which contribute new results in all areas of the Energy Engineering and allied fields. This multi disciplinary journal is devoted to the publication of high quality papers on theoretical and practical aspects of Energy Engineering.
Study of Forced Convection Heat Transfer with Single phase and mixture phase ...IOSRJMCE
In this study, forced convection heat transfer of nanoliquids is done using both single-phase and mixture-phase models and the results are compared with experimental results. The governing equations of the study here are discretized using the finite volume method. Hybrid differencing scheme is used to calculate the face values of the control volumes. A code is written using SIMPLER algorithm and then solved using the MATLAB engine. The mixture-phase model studied here, considers two slip mechanisms between nanoparticle and base-fluid, namely Brownian diffusion and thermophoresis. Al2O3-water nanofluid is used for the study of nanofluid and the study shows significant increase in convective heat transfer coefficient while the mixturephase model demonstrates slightly lower values than the single-phase model. The study is done with various nanoparticle concentrations and Reynolds numbers. With increasing particle concentration and Reynolds number, the convective heat transfer coefficient increases and as well as the shear stress. For low concentrations of the nanoparticle, Nusselt number is slightly lower than the base fluid and as the concentration increases, the Nusselt number also rises higher than the base fluid
IRJET- Numerical Investigation on the Heat Transfer Characteristics of Alumin...IRJET Journal
This document presents a numerical investigation of heat transfer characteristics of a double pipe heat exchanger using alumina-water nanofluid. The study examines the effects of nanoparticle concentration and volume flow rate on heat transfer coefficient, Nusselt number, pressure drop, and friction factor. It was found that adding nanoparticles significantly improved the thermal performance of the heat exchanger. The average heat transfer coefficient and Nusselt number of the base fluid increased by 26% and 12.5% respectively with a 4% nanoparticle volume concentration. Nanoparticle addition also enhanced pressure drop by around 10.11%. Heat exchanger effectiveness could be improved by approximately 16% using a 4% alumina nanoparticle concentration in the base fluid.
The document provides a literature review on the effects of nanofluids in enhancing thermophysical properties. It discusses how adding nanoparticles to base fluids can increase thermal conductivity. The summary discusses how decreasing nanoparticle size and increasing temperature and volume fraction can further increase thermal conductivity. Prior studies found thermal conductivity enhancement was highest for nanofluids with smaller nanoparticle sizes (<50nm) and at higher temperatures. The literature review examines several past studies that investigated these effects and relationships between properties.
This document provides an introduction to nanofluids, which are fluids containing nanometer-sized solid particles that are engineered to enhance thermal conductivity. Conventional heat transfer fluids have inherently poor thermal conductivity, limiting their effectiveness. While adding micrometer-sized particles provided some improvement, nanofluids offer even better conductivity. Even at very low volumes of nanoparticles, nanofluids can exhibit up to 40% higher thermal conductivity than conventional fluids. This is due to nanoparticles having a high surface area to volume ratio and thermal properties an order of magnitude higher than base fluids. Their small size allows nanoparticles to behave similarly to base fluid molecules, avoiding issues like clogging and sedimentation seen with microparticles. Nanofluids' enhanced stability and thermal
Effect Of Cuo-Distilled Water Based Nanofluids On Heat Transfer Characteristi...IJERA Editor
In this paper, the heat transfer and pressure drop characteristics of the distilled water and the copper oxide-distilled water based nanofluid flowing in a horizontal circular pipe under constant heat flux condition are studied. Copper oxide nanoparticles of 40nm size are dispersed in distilled water using sodium dodecyl sulphate as surfactant and sonicated the nanofluid for three hour. Both surfactant and sonication increases the stability of the nanofluid. The nanofluids are made in three different concentration i.e. 0.1 Vol. %, 0.25 Vol. % and 0.50 Vol. %. The thermal conductivity is measured by KD2 PRO, density with pycnometer, viscosity with Brookfield LVDV-III rheometer. The results show that the thermal conductivity increases with both temperature and concentration. The viscosity and density increases with concentration but decreases with temperature. The specific heat is calculated by model and it decreases with concentration. The experimental local Nusselt number of distilled water is compared with local Nusselt number obtained by the well known shah equation for laminar flow under constant heat flux condition for validation of the experimental set up. The relative error is 4.48 % for the Reynolds number 750.9. The heat transfer coefficient increases with increase in both flow rate and concentration. It increases from 14.33 % to 46.1 % when the concentration is increased from 0.1 Vol. % to 0.5 Vol. % at 20 LPH flow rate. Friction factor decreases with increase in flow rate. It decreases 66.54 % when the flow rate increases from 10 LPH to 30 LPH for 0.1 Vol. %.
Effect of nanofluid on heat transfer characteristics of double pipe heat exch...eSAT Journals
Abstract A nanofluid is a mixture of nano sized particles of size up to 100 nm and a base fluid. Typical nanoparticles are made of metals, oxides or carbides, while base fluids may be water, ethylene glycol or oil. The effect of nanofluid to enhance the heat transfer rate in various heat exchangers is experimentally evaluated recently. The heat transfer enhancement using nanofluid mainly depends on type of nanoparticles, size of nanoparticles and concentration of nanoparticles in base fluid. In the present paper, an experimental investigation is carried out to determine the effect of various concentration of Al2O3 nano-dispersion mixed in water as base fluid on heat transfer characteristics of double pipe heat exchanger for parallel flow and counter flow arrangement. The volume concentrations of Al2O3 nanofluid prepared are 0.001 % to 0.01 %. The conclusion derived for the study is that overall heat transfer coefficient increases with increase in volume concentration of Al2O3 nano-dispersion compared to water up to volume concentration of 0.008 % and then decreases. Keywords: Nanofluid, Heat Transfer Characteristics, Double Pipe Heat Exchagner, Al2O3 Nano-dispersion
Dive into the intricate world of mathematics through this thought-provoking and meticulously crafted presentation. We proudly present the groundbreaking research work of an MPhil student, a true testament to the dedication and intellectual prowess exhibited in unraveling new dimensions within the realm of mathematics.
🔍 Presentation Highlights:
Prepare to be captivated by a captivating journey into the depths of mathematical exploration. This presentation showcases a wealth of meticulously curated content, ranging from foundational concepts to cutting-edge theories. With a keen focus on innovation, this research endeavors to expand the boundaries of mathematical understanding.
📚 Topics Explored:
From abstract algebra to advanced calculus, and from number theory to geometric topology, this presentation encompasses a broad spectrum of mathematical domains. Whether you're a seasoned mathematician, a curious student, or simply intrigued by the beauty of numbers, this presentation promises to engage and enlighten.
🔬 Research Insights:
Delve into the mind of an MPhil student whose dedication to the subject has resulted in groundbreaking insights. The research work within this presentation unveils new perspectives, challenges conventional thinking, and paves the way for future mathematical exploration.
🧠 Intellectual Rigor:
Crafted with meticulous attention to detail, this presentation reflects not only the student's intellectual rigor but also their passion for mathematical inquiry. The dedication to unraveling complex theories and the commitment to fostering a deeper understanding of mathematics is evident in every slide.
🎓 Academic Excellence:
As a testament to academic excellence, this presentation is a showcase of the heights that can be achieved through relentless pursuit of knowledge. It encapsulates the essence of the student's journey as they progress towards their MPhil degree, solidifying their place within the academic community.
Join us in celebrating the pursuit of knowledge, innovation, and the boundless possibilities that mathematics offers. Whether you're a fellow researcher, a mathematics enthusiast, or someone simply curious about the beauty of numbers, this presentation promises to ignite your intellectual curiosity and leave you with a profound appreciation for the power of mathematical exploration.
Increasing Thermal Conductivity of a Heat Exchanger Using Copper Oxide Nano F...IJERA Editor
A Nano fluid is the evolving concept which is very rarely used in the many core industries. Nano fluids have
found a great application in heat exchangers by increasing the thermal conductivity. We have aimed to
increasing the heat transfer co-efficient by using copper oxide Nano fluid. The Nano particles are formed by
using precipitation method and their fluids are formed by adding surfactants to the base fluid. The comparative
study on the Heat exchanger is made by using the CuO Nano Fluid and Hot water. The analysis and the results
shows that the overall heat transfer rate increases when subjected to Nano Fluids. The ethylene glycol fluid used
along with copper oxide Nano fluid will offer resistance to fouling.
The document summarizes a presentation on convection heat transfer in nanofluids. It discusses nanofluid preparation techniques, heat transfer mechanisms like Brownian motion, clustering, and the effect of parameters like volume concentration on thermal conductivity and viscosity. It also reviews an experimental case study that investigated the density, viscosity, thermal conductivity and heat transfer capacity of aluminum oxide nanofluids and found linear relationships between these properties and nanoparticle concentration.
This document reviews research on the heat transfer of nanofluids when an electric or magnetic field is applied. It discusses how applied fields can affect the heat transfer performance and mechanisms of nanofluids. While studies show fields can significantly impact nanofluid heat transfer, there are differing opinions on their exact effects and mechanisms. The document aims to analyze the mechanism of thermal conductivity enhancement in nanofluids and how applied fields induce chaotic convection and heat transfer enhancement.
Effect of Radiation on Mixed Convection Flow of a Non-Newtonian Nan fluid ove...IJMER
International Journal of Modern Engineering Research (IJMER) is Peer reviewed, online Journal. It serves as an international archival forum of scholarly research related to engineering and science education.
Entropy generation and heat transfer rate for MHD forced convection of nanoli...Barhm Mohamad
This document summarizes a numerical study that investigates magnetohydrodynamic forced convection of nanofluid in a rectangular channel with an extended surface and three cylindrical blocks. The study examines the effects of Reynolds number, Hartmann number, Eckert number, and nanoparticle volume fraction on temperature distribution, stream function, entropy generation, and mean Nusselt number. Governing equations for steady, incompressible, laminar, two-dimensional flow are presented. Thermophysical properties of water, copper nanoparticles, and the nanofluid are provided.
NUMERICAL INVESTIGATION OF NATURAL CONVECTION HEAT TRANSFER FROM CIRCULAR CYL...IAEME Publication
In the present work, the enhancement of natural convection heat transfer utilizing nano fluids as working fluid from horizontal circular cylinder situated in a square enclosure is investigated numerically. Different types of nano particles were tested. The types of the nano fluids are Cu, Al2O3 and TiO3 with water as base fluid. A model is developed to analyze heat transfer performance of nano fluids inside an enclosure taking into account the solid particle dispersionrs on the flow and heat
transfer characteristics.
The document presents a numerical investigation of natural convection heat transfer from a circular cylinder inside a square enclosure using different types of nanofluids. Governing equations for the laminar, steady-state flow and heat transfer are presented. The equations are solved using the vorticity-stream function formulation and finite difference method. Results are obtained for Rayleigh numbers between 104-106, enclosure width to cylinder diameter ratio of 2.5, and nanofluid volume fractions from 0-0.2. Types of nanofluids investigated include water with Cu, Al2O3, and TiO3 nanoparticles. Results show Nusselt number and heat transfer increase with nanofluid volume fraction. Heat transfer is more enhanced at lower Ray
Porous media has two specifications: First its dissipation area is greater than the conventional fins that enhance heat convection. Second the irregular motion of the fluid flow around the individual beads mixes the fluid more effectively. Nanofluids are mixtures of base fluid with a very small amount of nanoparticles having dimensions from 1 to 100 nm, with very high thermal conductivities, so it would be the best convection heat transfer by using porous media and nanofluids. Thus studies need to be conducted involving nanofluids in porous media. For that, the purpose of this article is to summarize the published subjects respect to the enhancement of convective heat transfer using porous media and nanofluids and identifies opportunities for future research.
Mixed Convection of Variable Properties Al2O3-EG-Water Nanofluid in a Two-Dim...A Behzadmehr
In this paper, mixed convection of Al2O3-EG-Water nanofluid in a square lid-driven enclosure is investigated numerically. The focus of this study is on the effects of variable thermophysical properties of the nanofluid on the heat transfer characteristics. The top moving and the bottom stationary horizontal walls are insulated, while the vertical walls are kept at different constant temperatures. The study is carried out for Richardson numbers of 0.01–1000, the solid volume fractions of 0–0.05 and the Grashof number of 104. The transport equations are solved numerically with a finite volume approach using the SIMPLER algorithm. The results show that the Nusselt number is mainly affected by the viscosity, density and conductivity variations. For low Richardson numbers, although viscosity increases by increasing the nanoparticles volume fraction, due to high intensity convection of enhanced conductivity nanofluid, the average Nusselt number increases for both constant and variable cases. However, for high Richardson numbers, as the volume fraction of nanoparticles increases heat transfer enhancement occurs for the constant properties cases but deterioration in heat transfer occurs for the variable properties cases. The distinction is due to underestimation of viscosity of the nanofluid by the constant viscosity model in the constant properties cases and states important effects of temperature dependency of thermophysical properties, in particular the viscosity distribution in the domain.
Practical eLearning Makeovers for EveryoneBianca Woods
Welcome to Practical eLearning Makeovers for Everyone. In this presentation, we’ll take a look at a bunch of easy-to-use visual design tips and tricks. And we’ll do this by using them to spruce up some eLearning screens that are in dire need of a new look.
Maximize Your Content with Beautiful Assets : Content & Asset for Landing Page pmgdscunsri
Figma is a cloud-based design tool widely used by designers for prototyping, UI/UX design, and real-time collaboration. With features such as precision pen tools, grid system, and reusable components, Figma makes it easy for teams to work together on design projects. Its flexibility and accessibility make Figma a top choice in the digital age.
Discovering the Best Indian Architects A Spotlight on Design Forum Internatio...Designforuminternational
India’s architectural landscape is a vibrant tapestry that weaves together the country's rich cultural heritage and its modern aspirations. From majestic historical structures to cutting-edge contemporary designs, the work of Indian architects is celebrated worldwide. Among the many firms shaping this dynamic field, Design Forum International stands out as a leader in innovative and sustainable architecture. This blog explores some of the best Indian architects, highlighting their contributions and showcasing the most famous architects in India.
ARENA - Young adults in the workplace (Knight Moves).pdfKnight Moves
Presentations of Bavo Raeymaekers (Project lead youth unemployment at the City of Antwerp), Suzan Martens (Service designer at Knight Moves) and Adriaan De Keersmaeker (Community manager at Talk to C)
during the 'Arena • Young adults in the workplace' conference hosted by Knight Moves.
International Upcycling Research Network advisory board meeting 4Kyungeun Sung
Slides used for the International Upcycling Research Network advisory board 4 (last one). The project is based at De Montfort University in Leicester, UK, and funded by the Arts and Humanities Research Council.
EASY TUTORIAL OF HOW TO USE CAPCUT BY: FEBLESS HERNANEFebless Hernane
CapCut is an easy-to-use video editing app perfect for beginners. To start, download and open CapCut on your phone. Tap "New Project" and select the videos or photos you want to edit. You can trim clips by dragging the edges, add text by tapping "Text," and include music by selecting "Audio." Enhance your video with filters and effects from the "Effects" menu. When you're happy with your video, tap the export button to save and share it. CapCut makes video editing simple and fun for everyone!
Architectural and constructions management experience since 2003 including 18 years located in UAE.
Coordinate and oversee all technical activities relating to architectural and construction projects,
including directing the design team, reviewing drafts and computer models, and approving design
changes.
Organize and typically develop, and review building plans, ensuring that a project meets all safety and
environmental standards.
Prepare feasibility studies, construction contracts, and tender documents with specifications and
tender analyses.
Consulting with clients, work on formulating equipment and labor cost estimates, ensuring a project
meets environmental, safety, structural, zoning, and aesthetic standards.
Monitoring the progress of a project to assess whether or not it is in compliance with building plans
and project deadlines.
Attention to detail, exceptional time management, and strong problem-solving and communication
skills are required for this role.
Fonts play a crucial role in both User Interface (UI) and User Experience (UX) design. They affect readability, accessibility, aesthetics, and overall user perception.
1. International Journal of Heat and Mass Transfer 54 (2011) 4376–4388
Contents lists available at ScienceDirect
International Journal of Heat and Mass Transfer
journal homepage: www.elsevier.com/locate/ijhmt
Numerical investigation of effective parameters in convective heat transfer
of nanofluids flowing under a laminar flow regime
Ehsan Ebrahimnia-Bajestan a,⇑, Hamid Niazmand a, Weerapun Duangthongsuk b, Somchai Wongwises c,d
a
Department of Mechanical Engineering, Ferdowsi University of Mashhad, Mashhad, Iran
b
Department of Mechanical Engineering, South-East Asia University, Bangkok, Thailand
c
Fluid Mechanics, Thermal Engineering and Multiphase Flow Research Laboratory (FUTURE), Department of Mechanical Engineering,
King Mongkut’s University of Technology Thonburi, Bangmod, Bangkok 10140, Thailand
d
The Royal Institute of Thailand, Academy of Science, Sanam Sueapa, Dusit, Bangkok 10300, Thailand.
a r t i c l e i n f o a b s t r a c t
Article history: This article presents a numerical investigation on heat transfer performance and pressure drop of nano-
Received 3 December 2010 fluids flows through a straight circular pipe in a laminar flow regime and constant heat flux boundary
Received in revised form 29 April 2011 condition. Al2O3, CuO, carbon nanotube (CNT) and titanate nanotube (TNT) nanoparticles dispersed in
Accepted 29 April 2011
water and ethylene glycol/water with particle concentrations ranging between 0 and 6 vol.% were used
Available online 27 May 2011
as working fluids for simulating the heat transfer and flow behaviours of nanofluids. The proposed model
has been validated with the available experimental data and correlations. The effects of particle concen-
Keywords:
trations, particle diameter, particles Brownian motions, Reynolds number, type of the nanoparticles and
Nanofluids
Heat transfer performance
base fluid on the heat transfer coefficient and pressure drop of nanofluids were determined and discussed
Pressure drop in details. The results indicated that the particle volume concentration, Brownian motion and aspect ratio
Numerical study of nanoparticles similar to flow Reynolds number increase the heat transfer coefficient, while the nano-
Thermal conductivity particle diameter has an opposite effect on the heat transfer coefficient. Finally, the present study pro-
vides some considerations for the appropriate choice of the nanofluids for practical applications.
Ó 2011 Elsevier Ltd. All rights reserved.
1. Introduction thermophysical properties and flow characteristics of nanofluids
[3–6]. However, this article is aimed at reviewing only the novel
Common heat transfer fluids such as oil, water and ethylene literature considering convective heat transfer of nanofluids with
glycol have inherently poor thermal conductivity compared to a numerical approach. These studies are briefly described as
most solids. This problem is the primary obstacle to the high follows.
compactness, light in weight and effectiveness of heat exchangers. Mirmasoumi and Behzadmehr [7] reported the effect of nano-
In order to enhance the thermal conductivity of conventional heat particle diameter on convective heat transfer performance of
transfer fluids, it has been tried to develop a new type of modern Al2O3/water nanofluid flowing under a fully developed laminar
heat transfer fluid by suspending ultrafine solid particles in base flow regime numerically. In their study, a two-phase mixture mod-
fluids. In 1993, Masuda et al. [1] studied the heat transfer perfor- el was used. The results demonstrated that the heat transfer coef-
mance of liquids with solid nanoparticles suspension. However, ficient of the nanofluid dramatically increases with decreasing the
the term of ‘‘nanofluid’’ was first named by Choi [2] in 1995, and diameter of nanoparticle. Moreover, the results also indicated that
successively gained popularity. Because of the extensively greater nanoparticle diameter has no significant effect on the skin friction
thermal conductivity and heat transfer performance of the nanofl- coefficient.
uids as compared to the base fluids, they are expected to be ideally Kalteh et al. [8] numerically studied forced convective heat
suited for practical applications. transfer of Cu/water nanofluid inside an isothermally heated
Since a decade ago, research publications related to the use of microchannel under a laminar flow regime. An Eulerian two-fluid
nanofluids as working fluids have been reported both numerically model was used to simulate the heat transfer characteristic of
and experimentally. There are also some review papers that the nanofluid. The results indicated that the heat transfer perfor-
elaborate on the current stage in the thermal behaviours, mance increases with increasing Reynolds number as well as
particle volume fraction. On the contrary, heat transfer enhance-
ment increases with decreasing nanoparticle diameter. Finally,
⇑ Corresponding author. Tel.: +98 915 300 6795; fax: +98 511 876 3304. the results also showed that the pressure drop of nanofluids is
E-mail address: ehsan.ebrahimnia@gmail.com (E. Ebrahimnia-Bajestan). slightly higher than that of base fluids.
0017-9310/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved.
doi:10.1016/j.ijheatmasstransfer.2011.05.006
2. E. Ebrahimnia-Bajestan et al. / International Journal of Heat and Mass Transfer 54 (2011) 4376–4388 4377
Mirmasoumi and Behzadmehr [9] investigated the laminar indicated that the average Nusselt number of the nanofluid in-
mixed convection heat transfer of Al2O3/water nanofluid flowing creases with increasing particle concentration. In contrast, the re-
through a horizontal tube numerically. A two-phase mixture mod- sults also showed that the bulk temperature of the nanofluid
el was used to describe the hydrodynamic and thermal behaviour decreases with increasing particle concentration.
of the nanofluid. The numerical results indicated that in the fully Akbarinia and Laur [18] presented the laminar mixed convec-
developed region the particle concentration has insignificant ef- tion heat transfer of Al2O3/water nanofluid flows in a circular
fects on the hydrodynamic parameters, while it has important ef- curved tube numerically. A two-phase mixture model and the
fects on the thermal parameters. Moreover, the results showed control-volume technique were used to investigate the effect of
that nanoparticle concentration is higher at the bottom of the test particle diameter on the hydrodynamic and thermal parameters.
tube and at the near wall region. Their results indicated that the Nusselt number and secondary flow
Akbarinia [10] and Akbarinia and Behzadmehr [11] numerically decrease with increasing the particle diameter and uniform distri-
investigated the fully developed laminar mixed convection of bution of nanoparticles is observed.
Al2O3/water nanofluid flowing through a horizontal curved tube. Zeinali Heris et al. [19] numerically investigated the convective
In their studies, three-dimensional elliptic governing equations heat transfer of nanofluid in a circular tube with constant wall
were used. The effects of the buoyancy force, centrifugal force temperature, employing a dispersion model. Their results showed
and particle concentration on the heat transfer performance were that decreasing nanoparticle size and increasing nanoparticle con-
presented. The results showed that the particle concentration has centration augment the heat transfer coefficient.
no direct effect on the secondary flow, axial velocity and skin fric- Raisi et al. [20] carried out a numerical study on laminar con-
tion coefficient. However, when the buoyancy force is more impor- vective heat transfer of Cu/water nanofluid inside a microchannel
tant than the centrifugal force, the effect of particle concentration with slip and no slip boundary conditions. They investigated the ef-
on the entire fluid temperature can affect the hydrodynamic fect of different parameters such as Reynolds number, particle con-
parameters. Moreover, the results also indicated that the buoyancy centration, and slip velocity coefficient on the nanofluid heat
force decreases the Nusselt number whereas the particle concen- transfer characteristics. The results indicated that the particle con-
tration has a positive effect on the heat transfer enhancement centration and slip velocity coefficient have significant effects on
and on the skin friction reduction. the heat transfer rate at high Reynolds numbers.
Izadi et al. [12] studied the hydrodynamic and thermal behav- Ghasemi and Aminossadati [21] investigated the natural con-
iours of an Al2O3/water nanofluid flowing through an annulus vective heat transfer of CuO/water nanofluid inside an inclined
under a laminar flow regime. In their study, a single-phase model enclosure with top and bottom wall at different temperatures.
was used for nanofluid simulation. The results indicated that the The effects of Rayleigh number, inclination angle, and particle con-
particle volume concentration has no significant effect on the centration on heat transfer performance were studied. The results
dimensionless axial velocity, but affects the temperature field showed that the flow pattern, temperature field and heat transfer
and increases the heat transfer coefficient. rate are affected by inclination angle at high Rayleigh numbers.
He et al. [13] numerically studied the convective heat transfer Furthermore, it was found that the heat transfer rate is maximised
of a nanofluid with TiO2 nanoparticles dispersed in water under at specific particle concentration and inclination angle.
laminar flow conditions. A single-phase model and combined Euler Zhou et al. [22] presented the lattice Boltzman method (LB
and Lagrange methods were used to investigate the effects of vol- method) to study the microscale characteristics of the multicom-
ume concentration, Reynolds number and aggregate size on the ponent flow of nanofluids. In this method, the computation domain
convective heat transfer and flow behaviour of the nanofluid. Their was separated into fine mesh and coarse mesh regions, respec-
results indicated that the nanofluid significantly enhances the Nus- tively. The multicomponent LB method was used in the fine mesh
selt number, especially in the entrance region. Moreover, the region and the single-component LB method was applied in the
numerical results were consistent with experimental data. coarse mesh region. The results indicated that the present model
Bianco et al. [14] investigated the heat transfer performance of can be used to predict the microscopic characteristics of the
an Al2O3/water nanofluid flowing through a circular tube under a nanofluid and the computational efficiency can be significantly
laminar flow regime numerically. A single-phase model and two- improved.
phase model were used to determine the heat transfer coefficient Although numerous papers are currently available on the
of the nanofluid. The results demonstrated that the heat transfer numerical study of laminar convective heat transfer of nanofluids,
performance increases with increasing Reynolds number as well there is no comprehensive study on different effective parameters
as particle volume concentration. Moreover, differences in the in this field. The effect of several parameters such as nanoparticle
average heat transfer coefficient between the single-phase and shape, based fluid type and nanoparticle material are not consid-
two-phase models were observed as approximately 11%. ered in literature. On the other hand, naturally the increase in heat
Kumar et al. [15] used a single-phase thermal dispersion model transfer performance due to the nanofluids is accompanied by
to numerically investigate the thermal properties and flow field several undesirable effects such as an increase in pressure drop.
of a Cu/water nanofluid in a thermally driven cavity. The results Therefore, it needs to find the suitable nanofluid for optimum oper-
indicated that the Grashof number, particle volume fraction and ation. No significant attention is paid to find some criteria for the
particle shape factor augment the average Nusselt number of choice of appropriate nanofluids in different heat transfer applica-
nanofluids. tions. In the present study a modified single-phase model for pre-
Talebi et al. [16] presented the numerical formulation to evalu- dicting the heat transfer performance of nanofluids is proposed
ate the laminar mixed convection heat transfer of Cu/water nano- and a home-made FORTRAN computer program is developed. The
fluid flowing through a square lid-driven cavity. They found that, at model has been validated against the measured data of Kim et al.
a given Reynolds number, the particle concentration affects the [23] and the predicted values from Shah and London [24] for the
thermal behaviour and flow characteristic at larger Rayleigh num- base fluid. The effects of particle concentration, mean particle
bers. Moreover, the effect of particle concentration decreased with diameter, Reynolds number, Brownian motion, nanoparticle mate-
increasing Reynolds number. rial and shape, and type of base fluid on the heat transfer perfor-
Shahi et al. [17] reported a numerical investigation to simulate mance of nanofluids are then investigated in detail. Finally, some
the heat transfer performance of Cu/water nanofluid flowing guidelines related to choice of the appropriate nanofluid for partic-
through a square cavity under a laminar flow regime. Their results ular applications are provided.
3. 4378 E. Ebrahimnia-Bajestan et al. / International Journal of Heat and Mass Transfer 54 (2011) 4376–4388
2. Mathematical modelling thermal conductivity and viscosity of the nanofluids according to
the first method.
Normally, two different approaches can be used in predicting 0:0475745 0:42561
the heat transfer performance of nanofluids. One is the two-phase le ¼ À0:0001953 þ À
T T2
model, where solid particles are treated as a solid phase in the base
fluid, and the other is the single-phase model, where the presence
for 20 C 6 T 6 80 C ð6Þ
of the nanoparticles is accounted for by introducing the effective
thermophysical properties for the nanofluid. A single-phase model ke ¼ 0:65 þ 4:864 Â 10À7 T 3 for 22 C 6 T 6 52 C ð7Þ
is simpler to implement and requires less computational time, and where T is the temperature in Celsius. However, it should be men-
therefore, adopted here to describe the heat transfer characteristics tioned that above correlations are valid only for Al2O3/water nano-
of nanofluids flowing through a straight circular tube under con- fluid containing 3 vol.% of suspended particles.
stant wall heat flux and laminar flow regime, as shown in Fig. 1. As for the second method, the Vajjha et al.’s [25] model is taken
On the basis of this model, the governing equations are as follows. for viscosity with two parameters A and B, which are determined
For continuity equation: according to the experimental data of Kim et al. [23].
ZZ
qe ~ Á d~ ¼ 0:
V A ð1Þ le ¼ lf ðTÞA expðB/Þ ð8Þ
This correlation applies for 20 °C 6 T 6 90 °C and 1% 6 / 6 10%,
For momentum equation:
with A = 0.9 and B = 10.0359.
Z ZZ ZZ ZZ For thermal conductivity, the model presented by Koo and Kle-
@~
V ~q ~ Á d~ ¼ À
qe d8 þ V eV A p~ Á d~ þ
n A le r~ Á d~
~V A ð2Þ instreuer [26] and modified by Vajjha and Das [27] is employed.
8 @t
The model consists of static thermal conductivity based on the
For energy equation: Maxwell’s theory and dynamic thermal conductivity to include
Z ZZ ZZ Brownian motion of nanoparticles. This model is expressed as
@T
ðqC p Þe d8 þ ðqC p Þe T ~ Á d~ ¼
V A ke rT Á d~
~ A ð3Þ follows:
8 @t
kp þ 2kf À 2ðkf À kp Þ/
where ~ p, T, t, , ~ and ~ are the velocity vector, pressure, temper-
V, A n ke ¼ kf þ ð5 Â 104 b/qf C p;f Þ
kp þ 2kf þ ðkf À kp Þ/
ature, time, volume, cross-sectional area vector and normal unit sffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi
vector, respectively. The effective thermophysical properties of jðT þ 273:15Þ
 f ðT; /Þ ð9Þ
the nanofluid indicated by the subscript e are density (q), thermal qp dp
conductivity (k), dynamic viscosity (l), and heat capacity (Cp). These
effective properties are modelled as temperature dependent vari- ðT þ 273:15Þ
ables using available correlations and experimental data as follows. f ðT; /Þ ¼ ð2:8217 Â 10À2 / þ 3:917 Â 10À3 Þ
ðT 0 þ 273:15Þ
Density:
þ ðÀ3:0669  10À2 / À 3:91123  10À3 Þ ð10Þ
qe ð/; TÞ ¼ ð1 À /Þqf ðTÞ þ /qp ð4Þ
Heat capacity: b ¼ 8:4407ð100/ÞÀ1:07304 ð11Þ
ð1 À /ÞðqðTÞC p ðTÞÞf þ /ðqp C p Þp where j is the Boltzmann constant (1.381 Â 10À23 J/K), dp is the
C p;e ð/; TÞ ¼ ð5Þ nanoparticle diameter (m), and T is the temperature (°C). T0 = 0 °C
ð1 À /Þqf ðTÞ þ /qp
is the reference temperature. The correlation is valid for
where / is the volume fraction of the nanoparticles, and the sub- 25 °C 6 T 6 90 °C and the volume fractions between 1% and 10%
scripts p and f indicate the nanoparticle and base fluid, respectively. for Al2O3 nanofluids [27]. It should be mentioned that all thermo-
Regarding the dynamic viscosity and thermal conductivity of physical properties of the base fluid (lf, kf, Cp,f and qf) are consid-
nanofluids two different methods have been considered. In the first ered as functions of temperature. For water as the base fluid,
method, available measured data of these properties in static con- density, heat capacity and thermal conductivity are obtained from
dition are used. However, in the second method, available models the curve-fits applied to available data [28], while for dynamic vis-
for dynamic viscosity and thermal conductivity of nanofluids, cosity the following correlation is employed [29]:
where different effects such as base fluid type, Brownian motions,
lwater ¼ 0:00002414 Â 10½247:8=ðTþ133ÞŠ ð12Þ
volume concentration, and nanoparticle diameters are also in-
cluded are employed. Clearly, these models are designed to accu- The above methods for effective viscosity (Eqs. (6) and (8)) have
rately predict the heat transfer coefficient. been compared with measured data of Kim et al. [23] for 3.0 vol.%
In the present study, the measured data of Kim et al. [23] is used Al2O3/water nanofluids, where reasonable agreements are
to develop the following correlations for predicting the effective observed (Fig. 2). Similarly, the temperature variations of thermal
L=2m
Flow
D= 4.57 mm
D
x
q = const.
Fig. 1. Flow geometry and numerical grid distributions.
4. E. Ebrahimnia-Bajestan et al. / International Journal of Heat and Mass Transfer 54 (2011) 4376–4388 4379
conductivity according to Eqs. (7) and (9) have been compared walls. For the thermal field, constant heat flux of 60 W (2089.56 W/
with the measured data of Kim et al. [23] as shown in Fig. 3. It m2) and the inlet temperature of 22 °C are employed correspond-
can be seen that Eq. (9) over predicts the thermal conductivity as ing to the data of Kim et al. [23], while constant temperature gra-
compared to the measured data, however it can predict the heat dient is applied at the outlet.
transfer coefficient more accurately as compared to Eq. (7) as will In order to simulate the nanofluid flow, pipe geometry with
be discussed later. 4.57 mm in diameter and 2 m long has been adopted according
to the flow geometry in the experimental work of Kim et al. [23]
as shown in Fig. 1. The problem under investigation is steady, how-
3. Solution methodology ever, in the numerical scheme the steady solution is obtained
through sufficient integrations in time. The governing equations
In order to evaluate the heat transfer coefficient of nanofluids are solved numerically in a body-fitted coordinate system using a
numerically, the following assumptions are required. control-volume technique. The numerical solution is based on a
As for boundary conditions for velocity filed, a uniform velocity projection-type method which solves the flow field in two steps.
profile is assumed at the inlet, while zero gradients are applied to Firstly, an intermediate velocity field is obtained using the avail-
all hydrodynamic variables at the outlet, with no-slip condition at able pressure field. Secondly, velocity and pressure corrections
.0014
Measured data of Kim et al. [23]
Eq. (6)
.0012 Eq. (8)
.0010
Viscosity (Pa.s)
.0008
.0006
.0004
.0002
10 20 30 40 50 60 70 80 90
o
Temperature ( C)
Fig. 2. Comparison of the predicted viscosity using Eqs. (6) and (8) with the measured data.
.90
Measured data of Kim et al. [23]
Eq. (7)
.85 Eq. (9)
Thermal conductivity (W/mK)
.80
.75
.70
.65
.60
10 20 30 40 50 60 70
Temperature (oC)
Fig. 3. Comparison of the predicted thermal conductivity using Eqs. (7) and (9) with the measured data.
5. 4380 E. Ebrahimnia-Bajestan et al. / International Journal of Heat and Mass Transfer 54 (2011) 4376–4388
are calculated from a Poisson equation designed to satisfy the con- 4. Model validation
tinuity equation. The numerical scheme was originally developed
by Chorin [30] and improved further by Dwyer [31] as well as Ren- For validating the present numerical scheme, the axial varia-
ksizbulut and Niazmand [32]. tions of the local Nusselt number have been compared with the
Moreover, extensive computations have been performed to experimental data of Kim et al. [23] and the results of Shah and
identify the number of grid points that produce reasonably grid London [24] as shown in Fig. 5. A laminar water flow in a straight
independent results. In Fig. 4 the grid resolution effects on the axial circular pipe geometry, as mentioned above, has been considered
variations of the centreline velocity (nondimensionalized with the under the constant heat flux condition of 60 W (2089.56 W/m2)
inlet velocity) and the heat transfer coefficient for just four differ- at Reynolds number of 1620. The Shah and London [24] equa-
ent mesh distributions are presented. It is clear that the grid sys- tion for the axial variations of the local Nusselt number is
tem of 41 Â 50 Â 150 points in respective directions of radial, expressed as:
azimuthal, and axial adequately resolve the velocity and thermal 8
3:302xÀ1=3 À 1;
à xà 6 0:00005
fields with reasonable accuracy. Uniform grid spacing is used in
the azimuthal direction, while the expansion ratios of 1.15 and NuðxÞ ¼ 1:302xÀ1=3 À 0:5;
à 0:00005 xà 0:0015
:
1.02 are employed in the radial and axial directions. 4:264 þ 8:68ð103 xà ÞÀ0:506 expðÀ41xà Þ; xà 0:001
ð13Þ
(a) 2.0
1.8
Dimensionless velocity
r θ x
1.6 21 x 30 x 70
41 x 50 x 150
51 x 50 x 170
61 x 50 x 190
1.4
1.2
1.0
0.0 .5 1.0 1.5 2.0
x (m)
(b) 2500
Heat transfer coefficient (W/m K)
2
2000
r θ x
21 x 30 x 70
41 x 50 x 150
1500 51 x 50 x 170
61 x 50 x 190
1000
500
0.0 .5 1.0 1.5 2.0
x (m)
Fig. 4. Grid resolution effects on the axial variations of (a) dimensionless centreline velocity and (b) heat transfer coefficient for 6.0 vol.% Al2O3/water nanofluid at Reynolds
number of 1460.
6. E. Ebrahimnia-Bajestan et al. / International Journal of Heat and Mass Transfer 54 (2011) 4376–4388 4381
x=D
where xà ¼ Re Pr. Excellent agreements between the results can be Other numerical scheme validations for nanofluids can be found
observed in Fig. 5. in Ebrahimnia-Bajestan et al. [33], which are not repeated here for
For the validation of the effective nanofluid properties models, conciseness.
the convective heat transfer of nanofluid in a straight pipe has been
considered. Fig. 6 shows the axial variations of heat transfer coef-
ficient of Al2O3/water nanofluid containing 3.0 vol.% of nanoparti- 5. Results and discussion
cles for Reynolds number of 1460. The results indicate that the
second method (Eqs. (8) and (9)) agrees better with the measured As shown in Fig. 6, the second method of nanofluid properties
data of Kim et al. [23] as compared to the first method (Eqs. (6) and models predicts the heat transfer coefficient more accurately than
(7)). This implies that the changes in thermal conductivity of nano- the first method. In addition, the second method is more general
fluids at static condition cannot justify the enhancement in heat than the first method, which is only valid for 3.0 vol.% Al2O3/water.
transfer coefficient of nanofluids and a model, which adjusts the Therefore, the second method has been employed for the evalua-
thermal conductivity to accurately estimate the heat transfer coef- tions of the effective thermal conductivity and viscosity in all
ficient, is required. numerical computations reported here. Moreover, the effects of
30
Measured data of Kim et al. [23]
Present model
25
Shah and London [24]
20
Nusselt number
15
10
5
0
0.0 .5 1.0 1.5 2.0
x (m)
Fig. 5. Comparison of the axial variations of the Nusselt number with available data in literature at Reynolds number of 1620.
2000
Measured data of Kim et al. [23]
1800 Present model (Using Eqs. 6 7)
Present model (Using Eqs. 8 9)
Heat transfer coefficient (W/m K)
2
1600
1400
1200
1000
800
600
400
0.0 .5 1.0 1.5 2.0
x (m)
Fig. 6. Comparison of the local heat transfer coefficient with measured data of 3.0 vol.% Al2O3/water nanofluid at Reynolds number of 1460.
7. 4382 E. Ebrahimnia-Bajestan et al. / International Journal of Heat and Mass Transfer 54 (2011) 4376–4388
several parameters on the convective heat transfer characteristics 5.2. The effect of nanoparticle diameter
of nanofluids will be examined in detail.
The effect of nanoparticle diameter on the heat transfer perfor-
mance of nanofluid for Reynolds number of 1460 and heat flux of
5.1. The effect of nanoparticle concentration 2089.56 W/m2 is shown in Fig. 8. The results show that the nano-
fluid with smaller nanoparticle diameter slightly increases the heat
Fig. 7 shows the effect of particle volume concentration on the transfer coefficient as compared to the larger particle diameter,
heat transfer coefficient along the pipe for Reynolds number of especially at lower volume concentrations. In general, according
1460 and heat flux of 2089.56 W/m2. The results indicate that to Eq. (9) the nanoparticle diameter has a negative effect on the
the heat transfer coefficient of nanofluid increases with increasing thermal conductivity and consequently on the heat transfer
particle volume concentration. According to Eq. (9), nanofluids coefficient.
with higher particle concentrations have higher static and dynamic
thermal conductivities, which in turn increase the heat transfer 5.3. The effect of Reynolds number
coefficient. For example, in the case of 6.0 vol.%, the local heat
transfer coefficient is about 22% larger than pure water at the Fig. 9 presents the effect of Reynolds number on the heat
end of the pipe. transfer coefficient along the pipe for Al2O3/water nanofluid with
2000
water
1800 2.0 vol.%
Heat transfer coefficient (W/m K)
4.0 vol.%
2
6.0 vol.%
1600
1400
1200
1000
800
600 Particle type : Al2O3
Re = 1460
400
0.0 .5 1.0 1.5 2.0
x (m)
Fig. 7. Axial variations of heat transfer coefficient for different particle volume concentrations of Al2O3/water nanofluid at Reynolds number of 1460.
2000
dp = 20 nm dp = 100 nm
1800 2.0 vol.% 2.0 vol.%
Heat transfer coefficient (W/m K)
6.0 vol.% 6.0 vol.%
2
1600
1400
1200
1000
800
600 Particle type : Al2O3
Re = 1460
400
0.0 .5 1.0 1.5 2.0
x (m)
Fig. 8. Axial variations of heat transfer coefficient for different particle diameters and concentrations of Al2O3/water nanofluid at Reynolds number of 1460.
8. E. Ebrahimnia-Bajestan et al. / International Journal of Heat and Mass Transfer 54 (2011) 4376–4388 4383
particle diameter of 20 nm. The results indicate that the heat trans- with the new nanofluid thermal conductivity model. Fig. 10 com-
fer coefficient of nanofluid increases with increasing Reynolds pares the axial variations of the heat transfer coefficient of Al2O3/
number. This is due to the fact that higher Reynolds numbers lead water nanofluid with and without Brownian motion effects on
to higher velocity and temperature gradients at the pipe wall. thermal conductivity model for various particle concentrations at
Reynolds number of 1460 and particle diameter of 20 nm. It is
clearly seen that the Brownian motion has significant effects on
5.4. The effect of Brownian motion of nanoparticles the heat transfer coefficient of the nanofluids.
According to Eq. (9), the second term is related to the dynamic
thermal conductivity and reflects the Brownian motion effects on 5.5. The effect of nanoparticle material
the thermal characteristics of nanofluids. In order to study the ef-
fects of Brownian motion on the heat transfer performance of The nanoparticle material affects the nanofluid properties and
nanofluids, Eq. (9) without the dynamic thermal conductivity term consequently is an important factor in heat transfer performance.
is used to simulate the convective heat transfer. It means that the In order to study the effect of nanoparticle material, the CuO/water
classical two-phase model of Maxwell is employed and compared nanofluid is selected to compare with the results of the Al2O3/
2000
dp = 20 nm
1800 Particle type : Al2O3
Heat transfer coefficient (W/m K)
φ = 0 vol.% φ = 4.0 vol.%
2
1600
Re = 500 Re = 500
Re = 1000 Re = 1000
1400 Re = 1460 Re = 1460
1200
1000
800
600
400
0.0 .5 1.0 1.5 2.0
x (m)
Fig. 9. Axial variations of heat transfer coefficient for different Reynolds numbers and particle concentrations of Al2O3/water nanofluid.
2200
φ = 2.0 vol.% φ = 6.0 vol.%
2000 with Brownian effect with Brownian effect
without Brownian effect without Brownian effect
Heat transfer coefficient (W/m K)
1800
2
1600
1400
1200
1000
800
Re = 1460
600
Particle type : Al2O3
400
0.0 .5 1.0 1.5 2.0
x (m)
Fig. 10. Effects of Brownian motion on the local heat transfer coefficient as a function of particle concentration for Al2O3/water nanofluid at Reynolds number of 1460.
9. 4384 E. Ebrahimnia-Bajestan et al. / International Journal of Heat and Mass Transfer 54 (2011) 4376–4388
water nanofluid. For the viscosity of the CuO/water nanofluid, Eq. 5.6. The effect of base fluid properties
(8) is employed, where constants A = 0.9197 and B = 22.8539 are
obtained following Vajjha et al. [25]. The thermal conductivity of Another important factor in the heat transfer characteristics of
CuO/water is evaluated based on Eqs. (9) and (10), however, the nanofluids is the type of base fluid. In addition to water, a common
parameter b is determined from [27] as expressed below, which base fluid consists of 60% ethylene glycol and 40% water (60% EG/
is valid for 25 °C 6 T 6 90 °C and 1% 6 / 6 6%. water) by mass has also been considered. This kind of heat transfer
fluid is common in cold regions of the world because of its low
b ¼ 9:881ð100/ÞÀ0:9446 ð14Þ freezing point. The thermophysical properties of 60% EG/water as
functions of temperature are obtained from [34] as follows:
As shown in Fig. 11, CuO/water nanofluids give higher convec-
tive heat transfer coefficients than the Al2O3/water nanofluids. q60%EG=water ¼ À2:475 Â 10À3 T 2 À 0:35T þ 1090:93 ð15Þ
For example, the heat transfer coefficient of 4.0 vol.% CuO/water
nanofluids is greater than that of the 6.0 vol.% Al2O3/water nanofl- C p;60%EG=water ¼ 4:248T þ 3042:74 ð16Þ
uids. This is because of the fact that the thermal conductivity of
CuO nanoparticles is much larger than the thermal conductivity k60%EG=water ¼ À3:196 Â 10À6 T 2 þ 7:54 Â 10À4 T þ 0:34 ð17Þ
of Al2O3 nanoparticles.
2000
CuO Al2O3
2.0 vol.% 2.0 vol.%
1800 4.0 vol.% 4.0 vol.%
Heat transfer coefficient (W/m K)
6.0 vol.% 6.0 vol.%
2
1600
1400
1200
1000
800 dp = 20 nm
Re = 1460
600
0.0 .5 1.0 1.5 2.0
x (m)
Fig. 11. Effects of particle type and particle concentration on the local heat transfer coefficient at Reynolds number of 1460 and particle diameter of 20 nm.
2000
Water
1800 60%EG/Water
Heat transfer coefficient (W/m K)
4.0 vol.% (Al2O3 - Water nanofluid)
2
1600 4.0 vol.% (Al2O3 - 60%EG/Water nanofluid)
1400
1200
1000
800
600
dp = 40 nm
Re = 1460
400
0.0 .5 1.0 1.5 2.0
x (m)
Fig. 12. Axial variations of heat transfer coefficient for different base fluids at Reynolds number of 1460 and particle diameter of 20 nm.
10. E. Ebrahimnia-Bajestan et al. / International Journal of Heat and Mass Transfer 54 (2011) 4376–4388 4385
Table 1
Properties of CNT/water and TNT/water nanofluids.
Nanofluids Nanoparticles aspect ratio Nanoparticles concentration (vol.%) Viscosity (Pa s) Thermal conductivity (W/m K)
k = a + bT + cT2
a b c
CNT/water 100 0.0384 0.00308 51.88156 À0.35487 6.14 Â 10À4
TNT/water %10 0.6 0.0015 0.42548 6.4 Â 10À4 0
2000
0.0384 vol.% (CNT-Water)
1800 0.6 vol.% (TNT-Water)
2.0 vol.% (Al2O3-Water)
Heat transfer coefficient (W/m K)
2
4.0 vol.% (Al2O3-Water)
1600
4.0 vol.% (CuO-Water)
1400
1200
1000
800
600
Re = 1460
400
0.0 .5 1.0 1.5 2.0
x (m)
Fig. 13. Effects of particle shape on the local heat transfer coefficient at Reynolds number of 1460.
3135:6 Table 2
l60%EG=water ¼ 0:001 exp À 8:9367 ð18Þ Different nanofluids flow conditions simulated in the present study and their
T þ 273:15
corresponding temperature increase, pressure drop, and pumping power.
These correlations are valid for 0 °C 6 T 6 97 °C. Type of Re dp (nm) / D T DP Pump
According to Vajjha and Das [27], Eqs. (8)–(11) are still applica- working fluids (vol.%) (°C) (Pa) power (W)
ble for the evaluation of viscosity and thermal conductivity of 60% Al2O3/60% EG/water 1460 20 4 0.56 43240 1.38
EG/water base nanofluids. 60% EG/water 1460 – – 0.68 26240 0.69
CNT/water 1460 Lp/dp 100 0.038 0.9 9625 0.16
In Fig. 12, the heat transfer coefficients of Al2O3 nanoparticles in
CuO/water 1460 20 6 1.05 8838 0.12
both water and 60% EG/water base fluids are compared. The results CuO/water 1460 20 4 1.52 3830 0.04
indicate that the heat transfer characteristics of nanofluids are TNT/water 1460 dp = 10, Lp = 100 0.6 1.8 2241 0.017
strongly influenced by the type of the base fluid. Al2O3/water 1460 100 6 2.05 2020 0.014
Al2O3/water 1460 40 6 2.06 2020 0.014
Al2O3/water 1460 20 6 2.08 2020 0.014
5.7. The effect of nanoparticle shape CuO/water 1460 20 2 2.18 1670 0.011
Al2O3/water 1460 40 4 2.39 1416 0.008
Al2O3/water 1460 20 4 2.39 1417 0.008
It has been shown that nanofluids containing nanoparticles Al2O3/water 1460 20 3 2.52 1188 0.007
with a higher aspect ratio have better thermal properties [35,36]. Water 1620 – – 2.6 974 0.005
For example, the cylindrical nanoparticles give higher thermal con- Al2O3/water 1460 20 2 2.72 996 0.005
ductivity and heat transfer coefficient than the spherical nanopar- Al2O3/water 1460 100 2 2.72 995 0.005
Al2O3/water 1460 40 2 2.73 995 0.005
ticles. To study the effect of nanoparticle shape, two kinds of Water 1460 – – 2.78 869 0.004
cylindrical nanoparticles, which are CNT and TNT are used and Al2O3/water 1000 20 4 3.44 936 0.004
then compared with the nanofluids with spherical nanoparticles. Water 1000 – – 4.08 572 0.002
He et al. [35] studied the heat transfer performance of CNT/water Al2O3/water 500 20 4 6.91 438 0.0009
Water 500 – – 8.19 266 0.0004
nanofluid containing 0.1 wt.% (0.0384 vol.%) and TNT/water nano-
fluid containing 2.5 wt.% (0.6 vol.%) numerically and experimen-
tally. They indicated that, at a given temperature, the shear
viscosity of both nanofluids decreases with increasing shear rate, water and TNT/water nanofluids, respectively. They simulated the
exhibiting a shear thinning behaviour. Moreover, the shear viscos- convective heat transfer of nanofluids as both Newtonian and
ity approaches a constant minimum value at higher shear rate. The non-Newtonian fluids. Their results showed that the heat transfer
measured viscosity did not show an important change versus share coefficients based on the non-Newtonian model agree well with
rate, more than the shear rates of 200 1/s and 500 1/s for the CNT/ the measured data. Furthermore, they indicated that, when the
11. 4386 E. Ebrahimnia-Bajestan et al. / International Journal of Heat and Mass Transfer 54 (2011) 4376–4388
nanofluid is considered as Newtonian with the constant minimum On the other hand, because of the low aspect ratio of TNT (%10)
value of viscosity, the heat transfer coefficient has also reasonable and its lower thermal conductivity as compared with Al2O3, CuO
agreement with the result of non-Newtonian model. and CNT, the heat transfer coefficient of TNT/water nanofluid is
In the present work, the constant minimum value of viscosity lower than those. Yet, it should be mentioned that the concentra-
presented by He et al. [35] was adopted as the effective viscosity. tion of TNT is lower than Al2O3, CuO. The TNT/water nanofluid con-
Similarly, the thermal conductivity of nanofluids as a function of taining 0.6 vol.% nanoparticle shows approximately the same heat
temperature is taken from [35] as listed in Table 1. transfer coefficient as that of Al2O3/water nanofluid containing
Fig. 13 presents the comparison of axial heat transfer coeffi- 2 vol.%, which also indicates the considerable effect of nanoparticle
cients for nanoparticles with different aspect ratios at Reynolds shape on the heat transfer characteristics of nanofluids.
number of 1460. The results show that the heat transfer coefficient Thus far, several influential parameters on the heat transfer of
of the CNT/water nanofluid is significantly greater than that of the nanofluids are investigated; yet the important question is which
other nanofluids, which can be attributed to its large aspect ratio nanofluid is more appropriate for a specific application. In this arti-
(100) as listed in Table 1. In addition to the nanoparticle shape, cle, considering a constant wall heat flux condition, two important
the higher thermal conductivity of CNTs compared with Al2O3 factors are considered as the criteria for the choice of proper nano-
and CuO is the reason of substantial thermal characteristics fluids. These factors are pressure drop and temperature difference
enhancement of CNT/water nanofluids, even at low concentrations. along the pipe. For a constant wall heat flux condition with a given
2000
Particle type : Al2O3
Re = 1460
dP = 20 nm 1800
2.6
1600
ΔP (Pa)
ΔT ( C)
o
ΔT
2.4 1400
ΔP
1200
2.2
1000
0 1 2 3 4 5 6
Particle volume fraction (%)
Fig. 14. Temperature differences and pressure drops for different particle volume concentrations of Al2O3/water nanofluid at Reynolds number of 1460 and particle diameter
of 20 nm.
Particle type : CuO
2.6 8000
Re = 1460
dP = 20 nm
2.4
2.2 6000
ΔP (Pa)
ΔT ( C)
2.0
o
ΔT
1.8 ΔP
4000
1.6
1.4
2000
1.2
0 1 2 3 4 5 6
Particle volume fraction (%)
Fig. 15. Temperature differences and pressure drops for different particle volume concentrations of CuO/water nanofluid at Reynolds number of 1460 and particle diameter
of 20 nm.
12. E. Ebrahimnia-Bajestan et al. / International Journal of Heat and Mass Transfer 54 (2011) 4376–4388 4387
amount of heat transfer to the fluid, the lower temperature differ- motion, particle diameter, particle shape, particle material and
ence along the pipe can be considered as an advantage in some type of base fluid on the heat transfer performance of nanofluids
applications. On the other hand, lower pressure drop reduces the are examined in details. Major findings can be summarised as
pumping cost. follows:
In the view of these two criteria, all cases simulated in the pres-
ent study are listed in Table 2, which have been sorted by pressure – The predicted heat transfer coefficients based on the thermo-
drop. It can be concluded from the table that almost all cases with physical properties of nanofluids in a static condition are lower
lower pressure drops have higher temperature differences, which than the experimental data. This means that the static thermal
also implies that nanofluids should be selected according to the conductivity increase is not the only reason of convective heat
application requirements. transfer enhancement of nanofluids.
From Table 2 it is observed that considerable pressure drop are – A thermal conductivity model which considers the effect of
associated with high particle concentration of nanofluids, while Brownian motion of nanoparticles predicts the heat transfer
much less pressure drop has been reported in numerical studies coefficient of nanofluids more accurately as compared to the
of [37,38] for similar flow conditions. It must be emphasised that models based on the pure static conditions of the nanofluids.
the viscosity model, le ¼ lf ð1 À /ÞÀ2:5 , which has been used in – The particle volume concentration, Brownian motion and aspect
these studies produces much lower values for viscosity as com- ratio of nanoparticles similar to the flow Reynolds number
pared to the present experimental data [23] and consequently increase the heat transfer coefficient of nanofluids, while the
leads to relatively lower pressure drops. However, the applied vis- particle diameter has an opposite effect. Moreover, the heat
cosity model in the present study (Eq. (8)) represents the experi- transfer characteristics of nanofluids are strongly influenced
mental data with reasonable accuracy and therefore, the by the type of both base fluid and nanoparticle.
resulting pressure drops are higher. – There are several parameters to select the proper nanofluids for
Another related issue to the pressure drop is the relative in- convective heat transfer of nanofluids in pipes. These parame-
crease in viscosity with respect to thermal conductivity as the ters are the amount of heat transfer enhancement, pump power,
nanoparticle concentration increases. In general, the advantage of stability, cost, toxicity and chemical corrosion of pipe wall. Also,
the nanofluids for the heat transfer applications is directly related there are some other restrictions in the special applications
to the amount of the thermal conductivity increase, leading to the such as low freezing temperature nanofluids as the anti-refrig-
heat transfer enhancement, to the amount of the viscosity increase erant fluids in cold region.
associated with higher pressure drops. For the nanofluids used in
the present study, the viscosity of the base fluid increases faster
than its thermal conductivity as nanoparticle concentration in- Acknowledgements
creases, and therefore, the heat transfer enhancements come at
the expense of relatively considerable pressure drop. The authors wish to thank Ferdowsi University of Mashhad
Considering Table 2, the temperature increase along the pipe (Iran), South-East Asia University (Thailand), King Mongkut’s Uni-
and the pressure drop behave in an opposite manner. In Figs. 14 versity of Technology Thonburi (Thailand) for the valuable support
and 15 these parameters are plotted versus the particle volume in the present study. The fourth author would like to acknowledge
fraction to see if an optimum nanoparticle concentration for a spe- the Thailand Research Fund and the National Research University
cific application can be identified. Fig. 14 shows the Al2O3 nanopar- Project for financial supporting.
ticles in water with particle diameter of 20 nm and Reynolds
number of 1460. From this figure, the optimum choice for the References
Al2O3/water nanofluid is the volume fraction of about 4 vol.%,
which has more reasonable temperature increase and pressure [1] H. Masuda, A. Ebata, K. Teramae, N. Hishinuma, Alteration of thermal conduc-
tivity and viscosity of liquid by dispersing ultra-fine particles (dispersion of
drop. Similarly, Fig. 15 indicates that for the case of the CuO/water Al2O3, SiO2 and TiO2 ultra-fine particles), Netsu Bussei (in Japanese) 7 (4)
nanofluid with particle diameter of 20 nm and Reynolds number of (1993) 227–233.
1460, the proper choice is the volume fraction of about 3.7 vol.%. [2] S.U.S. Choi, Enhancing thermal conductivity of fluids with nanoparticles, in:
Proceedings of the 1995 ASME International Mechanical Engineering Congress
Another limitation for nanofluids applications is the toxicity of
and Exposition, ASME, New York, 1995, pp. 99–105.
nanoparticles. Clearly, the green nanofluids with no environmen- [3] W. Duangthongsuk, S. Wongwises, A critical review of convective heat transfer
tal, health and safety dangers are desirable. There are some studies of nanofluids, Renew. Sustain. Energy Rev. 11 (2007) 797–817.
on toxicity of nanoparticles considered in this article, Al2O3 [39], [4] V. Trisaksri, S. Wongwises, Critical review of heat transfer characteristics of the
nanofluids, Renew. Sustain. Energy Rev. 11 (3) (2007) 512–523.
CuO [40], CNT [41,42] and TiO2 [40]. Among them, the high toxicity [5] X.Q. Wang, A.S. Mujumdar, Heat transfer characteristics of nanofluids: a
of CuO nanoparticles has been reported [40]. Moreover, Bottini review, Int. J. Therm. Sci. 46 (1) (2007) 1–19.
et al. [42] indicated that CNTs nanofluids can be very toxic at high [6] L. Godson, B. Raja, D. Mohan Lal, S. Wongwises, Enhancement of heat transfer
using nanofluids – an overview, Renew. Sustain. Energy Rev. 14 (2) (2010)
particle concentrations. 629–641.
In addition, the economical justification is one of the important [7] S. Mirmasoumi, A. Behzadmehr, Effect of nanoparticles mean diameter on
considerations in nanofluid selection. In the present study, CNT/ mixed convection heat transfer of a nanofluid in a horizontal tube, Int. J. Heat
Fluid Flow 29 (2) (2008) 557–566.
water nanofluid with a low concentration of 0.038 vol.% but high [8] M. Kalteh, A. Abbassi, M. Saffar-Avval, J. Harting, Eulerian–Eulerian two-phase
heat transfer coefficient seems to be a low cost nanofluid as com- numerical simulation of nanofluid laminar forced convection in a
pared with the others. Finally, the chemical reaction of nanofluids microchannel, Int. J. Heat Fluid Flow 32 (1) (2011) 107–116.
[9] S. Mirmasoumi, A. Behzadmehr, Numerical study of laminar mixed convection
with the pipe wall is a consideration, especially in the case of sur- of a nanofluid in a horizontal tube using two-phase mixture model, Appl.
factants, which may affect the nanofluids applications. Therm. Eng. 28 (7) (2008) 717–727.
[10] A. Akbarinia, Impacts of nanofluid flow on skin friction factor and Nusselt
number in curved tubes with constant mass flow, Int. J. Heat Fluid Flow 29 (1)
6. Conclusions
(2008) 229–241.
[11] A. Akbarinia, A. Behzadmehr, Numerical study of laminar mixed convection of
The laminar convective heat transfer performance and pressure a nanofluid in horizontal curved tubes, Appl. Therm. Eng. 27 (8–9) (2007)
drop of different nanofluids flowing in a straight circular pipe un- 1327–1337.
[12] M. Izadi, A. Behzadmehr, D. Jalali-Vahida, Numerical study of developing
der a constant heat flux condition were numerically investigated. laminar forced convection of a nanofluid in an annulus, Int. J. Therm. Sci. 48
The effects of particle concentration, Reynolds number, Brownian (11) (2009) 2119–2129.
13. 4388 E. Ebrahimnia-Bajestan et al. / International Journal of Heat and Mass Transfer 54 (2011) 4376–4388
[13] Y. He, Y. Men, Y. Zhao, H. Lu, Y. Ding, Numerical investigation into the [27] R.S. Vajjha, D.K. Das, Experimental determination of thermal conductivity of
convective heat transfer of TiO2 nanofluids flowing through a straight tube three nanofluids and development of new correlations, Int. J. Heat Mass
under the laminar flow conditions, Appl. Therm. Eng. 29 (10) (2009) 1965– Transfer 52 (21–22) (2009) 4675–4682.
1972. [28] F.P. Incropera, D.P. DeWitt, T.L. Bergman, A.S. Lavine, Fundamentals of Heat
[14] V. Bianco, F. Chiacchio, O. Manca, S. Nardini, Numerical investigation of and Mass Transfer, sixth ed., John Wiley Sons, 2006. p. 949.
nanofluids forced convection in circular tubes, Appl. Therm. Eng. 29 (17) [29] R.W. Fox, A.T. McDonald, P.J. Pritchard, Introduction to Fluid Mechanics, sixth
(2009) 3632–3642. ed., John Wiley Sons, Berlin, 2004. p. 724.
[15] S. Kumar, S.K. Prasad, J. Banerjee, Analysis of flow and thermal field in [30] A.J. Chorin, Numerical solution of the Navier–Stokes equations for an
nanofluid using a single phase thermal dispersion model, Appl. Math. Model. incompressible fluid, Math. Comput. 22 (104) (1968) 745–762.
34 (3) (2010) 573–592. [31] H.A. Dwyer, Calculations of droplet dynamics in high temperature
[16] F. Talebi, A.H. Mahmoudi, M. Shahi, Numerical study of mixed convection environments, Prog. Energy Combust. Sci. 15 (2) (1989) 131–158.
flows in a square lid-driven cavity utilizing nanofluid, Int. Commun. Heat Mass [32] M. Renksizbulut, H. Niazmand, Laminar flow and heat transfer in the entrance
Transfer 37 (1) (2010) 79–90. region of trapezoidal channels with constant wall temperature, J. Heat
[17] M. Shahi, A.H. Mahmoudi, F. Talebi, Numerical study of mixed convective Transfer 128 (1) (2006) 63–74.
cooling in a square cavity ventilated and partially heated from the below [33] E. Ebrahimnia-Bajestan, H. Niazmand, M. Renksizbulut, Flow and heat transfer
utilizing nanofluid, Int. Commun. Heat Mass Transfer 37 (2) (2010) 201–213. of nanofluids with temperature dependent properties, in: Proceedings of the
[18] A. Akbarinia, R. Laur, Investigating the diameter of solid particles effects on a ASME 2010 Third Joint US–European Fluids Engineering Summer Meeting and
laminar nanofluid flow in a curved tube using a two phase approach, Int. J. Eighth International Conference on Nanochannels, Microchannels, and
Heat Fluid Flow 30 (4) (2009) 706–714. Minichannels, Montreal, 2010.
[19] S. Zeinali Heris, M. Nasr Esfahany, G. Etemad, Numerical investigation of [34] R. Strandberg, D.K. Das, Finned tube performance evaluation with nanofluids
nanofluid laminar convective heat transfer through a circular tube, Numer. and conventional heat transfer fluids, Int. J. Therm. Sci. 49 (3) (2010) 580–588.
Heat Transfer, Part A: Appl. 52 (11) (2007) 1043–1058. [35] Y. He, Y. Men, X. Liu, H. Lu, H. Chen, Y. Ding, Study on forced convective heat
[20] A. Raisi, B. Ghasemi, S.M. Aminossadati, A numerical study on the forced transfer of non-Newtonian nanofluids, J. Therm. Sci. 18 (1) (2009) 20–26.
convection of laminar nanofluid in a microchannel with both slip and no-slip [36] H. Chen, W. Yang, Y. He, Y. Ding, L. Zhang, C. Tan, A.A. Lapkin, D.V. Bavykin,
conditions, Numer. Heat Transfer, Part A: Appl. 59 (2) (2011) 114–129. Heat transfer and flow behaviour of aqueous suspensions of titanate
[21] B. Ghasemi, S.M. Aminossadati, Natural convection heat transfer in an inclined nanotubes (nanofluids), Powder Technol. 183 (1) (2008) 63–72.
enclosure filled with a water–CuO, Numer. Heat Transfer, Part A: Appl. 55 (8) [37] J. Li, C. Kleinstreuer, Thermal performance of nanofluid flow in microchannels,
(2009) 807–823. Int. J. Heat Fluid Flow 29 (4) (2008) 1221–1232.
[22] L. Zhou, Y. Xuan, Q. Li, Multiscale simulation of flow and heat transfer of [38] R. Chein, G. Huang, Analysis of microchannel heat sink performance using
nanofluid with lattice Boltzmann method, Int. J. Multiphase Flow 36 (5) (2010) nanofluids, Appl. Therm. Eng. 25 (17–18) (2005) 3104–3114.
364–374. [39] W. Lin, I. Stayton, Y. Huang, X.D. Zhou, Y. Ma, Cytotoxicity and cell membrane
[23] D. Kim, Y. Kwon, Y. Cho, C. Li, S. Cheong, Y. Hwang, J. Lee, D. Hong, S. Moon, depolarization induced by aluminum oxide nanoparticles in human lung
Convective heat transfer characteristics of nanofluids under laminar and epithelial cells A549, Toxicol. Environ. Chem. 90 (5) (2008) 983–996.
turbulent flow conditions, Curr. Appl Phys. 9 (2) (2009) e119–e123. [40] V. Aruoja, H.C. Dubourguiera, K. Kasemets, A. Kahru, Toxicity of nanoparticles of
[24] R.K. Shah, A.L. London, Laminar Flow Forced Convection in Ducts, Academic CuO, ZnO and TiO2 to microalgae Pseudokirchneriella subcapitata, Sci. Total
Press, New York, 1978. p.128. Environ. 407 (4) (2009) 1461–1468.
[25] R.S. Vajjha, D.K. Das, P.K. Namburu, Numerical study of fluid dynamic and heat [41] J. Miyawaki, M. Yudasaka, T. Azami, Y. Kubo, S. Iijima, Toxicity of single-walled
transfer performance of Al2 O3 and CuO nanofluids in the flat tubes of a carbon nanohorns, ACS Nano 2 (2) (2008) 213–226.
radiator, Int. J. Heat Fluid Flow 31 (4) (2010) 613–621. [42] M. Bottini, S. Bruckner, K. Nika, N. Bottini, S. Bellucci, A. Magrini, A.
[26] J. Koo, C. Kleinstreuer, A new thermal conductivity model for nanofluids, J. Bergamaschi, T. Mustelin, Multi-walled carbon nanotubes induce T
Nanopart. Res. 6 (6) (2004) 577–588. lymphocyte apoptosis, Toxicol. Lett. 160 (2) (2006) 121–126.