Semnan University Press
Journal of Heat and Mass Transfer Research(JHMTR)
2345-508X
2383-3068
1
1
2014
05
01
Effects of coupling on turbulent gas-particle boundary layer flows at borderline volume fractions using kinetic theory
1
8
EN
Maziar
Dehghan
Mechanical Engineering Department., Amirkabir University of Technology, Tehran, Iran
Hassan
Basirat Tabrizi
Mechanical Engineering Department., Amirkabir University of Technology, Tehran, Iran
hbasirat@aut.ac.ir
10.22075/jhmtr.2014.148
This study is concerned with the prediction of particles’ velocity in a dilute turbulent gas-solidboundary layer flow using a fully Eulerian two-fluid model. The closures required for equationsdescribing the particulate phase are derived from the kinetic theory of granular flows. Gas phaseturbulence is modeled by one-equation model and solid phase turbulence by MLH theory. Resultsof one-way and two-way coupled approaches are compared with the available experimental andnumerical results. Results show that one-way coupled approach is more efficient for particulatevelocity prediction in dilute flows. But, if the gas-phase flow characteristics are desired, the twowaycoupled approach should be used. Effects of free stream velocity on the coupling arediscussed.
Two-way coupled,Gas-Particle flow,Kinetic theory,Turbulent boundary layer
http://jhmtr.journals.semnan.ac.ir/article_148.html
http://jhmtr.journals.semnan.ac.ir/article_148_dca4e58d112e43fd2832c0e5b9fcee9c.pdf
Semnan University Press
Journal of Heat and Mass Transfer Research(JHMTR)
2345-508X
2383-3068
1
1
2014
05
01
Effect of magnetic field on the boundary layer flow, heat, and mass transfer of nanofluids over a stretching cylinder
9
16
EN
Aminreza
Noghrehabadi
Department of Mechanical Engineering, Shahid Chamran University of Ahvaz, Ahvaz, Iran
noghrehabadi@scu.ac.ir
Mohammad
Ghalambaz
Department of Mechanical Engineering, Shahid Chamran University of Ahvaz, Ahvaz, Iran
m.ghalambaz@gmail.com
Ehsan
Izadpanahi
Department of Mechanical Engineering, Shahid Chamran University of Ahvaz, Ahvaz, Iran
Rashid
Pourrajab
Department of Mechanical Engineering, Shahid Chamran University of Ahvaz, Ahvaz, Iran
10.22075/jhmtr.2014.149
The effect of a transverse magnetic field on the boundary layer flow and heat transfer of anisothermal stretching cylinder is analyzed. The governing partial differential equations for themagnetohydrodynamic, temperature, and concentration boundary layers are transformed into a setof ordinary differential equations using similarity transformations. The obtained ordinarydifferential equations are numerically solved for a range of non-dimensional parameters. Resultsshow that the presence of a magnetic field would significantly affects the boundary layer profiles.An increase in magnetic parameter would decrease the reduced Nusselt and Sherwood numbers.
Nanofluid,Stretching cylinder,magnetic field,Brownian motion,Thermophoresis
http://jhmtr.journals.semnan.ac.ir/article_149.html
http://jhmtr.journals.semnan.ac.ir/article_149_9aad9d7574b00a925fec3f564a023ce6.pdf
Semnan University Press
Journal of Heat and Mass Transfer Research(JHMTR)
2345-508X
2383-3068
1
1
2014
05
01
An experimental investigation of rheological characteristics of non- Newtonian nanofluids
17
23
EN
Milad
Tajik Jamal-Abad
Faculty of Mechanical Engineering, Semnan University, Semnan, Iran
Maziar
Dehghan
Faculty of Mechanical Engineering, Semnan University, Semnan, Iran
Seyfolah
Saedodin
Faculty of Mechanical Engineering, Semnan University, Semnan, Iran
Mohammad Sadegh
Valipour
Faculty of Mechanical Engineering, Semnan University, Semnan, Iran
msvalipour@semnan.ac.ir
Amirhossein
Zamzamian
Materials and Energy Research Center (MERC), Karaj, Iran
10.22075/jhmtr.2014.150
Rheological characteristics of Al2O3, CuO and TiO2 nano particles were investigated in oil asthe base fluid at 1 and 2 wt.%. Constitutive relations for non-Newtonian fluid were discussedbased on the power-law model. Measured viscosities of each nanofluid were used to evaluatethe power-law and consistency index. Results indicated that the nanofluid viscosity decreasedby increasing the concentration. Oil showed shear thickening behavior while nanofluids showedshear thinning behavior. An increase in nano-particle concentration caused a decrease in thepower-law index beside an increase in the consistency index. Moreover, the present studyshowed that the effective viscosity of fluids would be decreased by nanoparticle addition atsome wt.% and some shear rates. Furthermore, results showed that the classic models fornanofluid viscosity couldn’t predict their real values of nano fluid viscosity, as the measuredvalues are less than the predicted ones.
Nanofluids,viscosity,Rheological characteristics,Power-law index,Consistency index
http://jhmtr.journals.semnan.ac.ir/article_150.html
http://jhmtr.journals.semnan.ac.ir/article_150_401305767c71cb6aabc76faa75d3c22e.pdf
Semnan University Press
Journal of Heat and Mass Transfer Research(JHMTR)
2345-508X
2383-3068
1
1
2014
05
01
Entropy generation calculation for laminar fully developed forced flow and heat transfer of nanofluids inside annuli
25
33
EN
Roohollah
Rafee
Faculty of mechanical engineering, Semnan University, Semnan, Iran
rafee@semnan.ac.ir
10.22075/jhmtr.2014.151
In this paper, second law analysis for calculations of the entropy generation due to the flow andheat transfer of water-Al2O3 and ethylene glycol-Al2O3 nanofluids inside annuli is presented. Thephysical properties of the nanofluids are calculated using empirical correlations. Constant heatfluxes at inner surface of the annuli are considered and fully developed condition for fluid flowand heat transfer is assumed. The control volume approach is selected for calculation of theentropy generation. Total entropy generation for different values of the nanoparticles volumefractions at different geometrical ratios is obtained and compared with those of the base fluid.Also, the geometrical ratios at which the minimum entropy generation is achieved are presented.The results show that when the ratio of the annuli length to its hydraulic diameter (L/Dh) exceedssome critical values, adding of the nanoparticles is not efficient. For each value of thenanoparticles concentration, there is a length ratio (L/Dh) at which the entropy generation isminimized.
Second law of thermodynamics,Entropy generation,Nanofluids,Heat transfer,Annuli,Laminar flow
http://jhmtr.journals.semnan.ac.ir/article_151.html
http://jhmtr.journals.semnan.ac.ir/article_151_c39cb6485723d5489b60e3a2272e7cff.pdf
Semnan University Press
Journal of Heat and Mass Transfer Research(JHMTR)
2345-508X
2383-3068
1
1
2014
05
01
The optimization of inlet and outlet port locations of a vented square cavity
35
45
EN
Taher
Armaghani
Islamic azad university Mahdishahr branch, Department of engineering, Mahdishahr, Iran.
taherarmaghani@yahoo.com
Farhad
Talebi
Department of mechanical engineering, Semnan University, Semnan, Iran
ftalebi@semnan.ac.ir
Amir Houshang
Mahmoudi
Department of mechanical engineering, Semnan University, Semnan, Iran
amirhoshangm@gmail.com
M
Farzaneh Gord
Department of mechanical engineering, Shahrood University of Technology, Shahrood, Iran
10.22075/jhmtr.2014.152
In this study, mixed convection heat transfer and local and global entropy generation in aventilated square cavity have been investigated numerically. The natural convection effect isachieved by a constant heat flux imposed at the bottom wall and cooled by injecting a coldfollow. In order to investigate the effect of port location, four different placementconfigurations of the inlet and outlet ports are studied. In each case, external flow enters intothe cavity through an inlet port in the left side of the cavity and exits from the opposite side.The other boundaries are assumed adiabatic. The cavity is subjected to laminar flow of water.The investigation has been carried out for the Re=1000, and the Richardson number with therange of 0.0001(Global Entropy Generation), Heat Transfer Irreversibility (HTI) and Fluid FrictionIrreversibility (FFI) are calculated and compared. Then, the optimum inlet/outlet configurationhas been selected based on the minimum GEG and the maximum heat transfer.
Vented square cavity,Entropy generation,Heat transfer,Irreversibility,Fluid friction irreversibility
http://jhmtr.journals.semnan.ac.ir/article_152.html
http://jhmtr.journals.semnan.ac.ir/article_152_927bdd54aeb26a6e0a5e77b1b39891af.pdf
Semnan University Press
Journal of Heat and Mass Transfer Research(JHMTR)
2345-508X
2383-3068
1
1
2014
05
01
Experimental investigation and proposed correlations for temperaturedependent thermal conductivity enhancement of ethylene glycol based nanofluid containing ZnO nanoparticles
47
54
EN
Mohammad
Hemmat Esfe
Faculty of mechanical engineering, Semnan University, Semnan, Iran
m.hemmatesfe@gmail.com
Seyfolah
Saedodin
Faculty of mechanical engineering, Semnan University, Semnan, Iran
10.22075/jhmtr.2014.153
Experimental study of effective thermal conductivity of ZnO/EG nanofluid is presented in thisresearch. The nanofluid was prepared by dispersing Zno nanoparticles in ethylene glycol using asonicator and adding surfactant. Ethylene glycol based nanofluid containing ZnO nanoparticlewith a nominal diameter of 18 nm at different solid volume fractions (very low to high) atvarious temperatures was examined for the investigation. The thermal conductivity of nanofluidsis experimentally measured with THW method and it is found that the thermal conductivity ofnanofluids increase with the nanoparticle volume concentration and temperature. Also, based onexperimental values of thermal conductivity of nanofluid, three experimental models areproposed to predict thermal conductivity of nanofluids. The proposed models show reasonablyexcellent agreement with our experimental results.
Thermal conductivity,Heat transfer,Nanofluid,Thermophysical properties
http://jhmtr.journals.semnan.ac.ir/article_153.html
http://jhmtr.journals.semnan.ac.ir/article_153_9251c831bba6699048c766e91d9145a4.pdf
Semnan University Press
Journal of Heat and Mass Transfer Research(JHMTR)
2345-508X
2383-3068
1
1
2014
05
01
Boundary layer flow beneath a uniform free stream permeable continuous moving surface in a nanofluid
55
65
EN
Ioan
Pop
Department of Mathematics, Babes-Bolyai University, 400048 Cluj-Napoca, Romania
popm.ioan@yahoo.co.uk
Sarkhosh
Seddighi
Department of Mathematics and Institute for Mathematical Research, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor, Malaysia
Norfifah
Bachok
Department of Mathematics and Institute for Mathematical Research, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor, Malaysia
Fudziah
Ismail
Department of Mathematics and Institute for Mathematical Research, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor, Malaysia
10.22075/jhmtr.2014.154
The main purpose of this paper is to introduce a boundary layer analysis for the fluid flow andheat transfer characteristics of an incompressible nanofluid flowing over a permeable isothermalsurface moving continuously. The resulting system of non-linear ordinary differential equations issolved numerically using the fifth–order Runge–Kutta method with shooting techniques usingMatlab and Maple softwares. Numerical results are obtained for the velocity, temperature, andconcentration distributions, as well as the friction factor, local Nusselt number, and localSherwood number for several values of the parameters, namely the velocity ratio parameter,suction/injection parameter, and nanofluid parameters. The obtained results are presentedgraphically in tabular forms and the physical aspects of the problem are discussed.
Suction/injection,Moving surface,Nanofluid,Runge-Kutta method,Shooting techniques,Dual solutions
http://jhmtr.journals.semnan.ac.ir/article_154.html
http://jhmtr.journals.semnan.ac.ir/article_154_e40cc08957afcb290a5aeb7185e67c89.pdf