2017-09-26T16:07:48Z
http://jhmtr.journals.semnan.ac.ir/?_action=export&rf=summon&issue=27
Journal of Heat and Mass Transfer Research(JHMTR)
JHMTR
2345-508X
2345-508X
2014
1
1
Effects of coupling on turbulent gas-particle boundary layer flows at borderline volume fractions using kinetic theory
Maziar
Dehghan
Hassan
Basirat Tabrizi
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
2014
05
01
1
8
http://jhmtr.journals.semnan.ac.ir/article_148_dca4e58d112e43fd2832c0e5b9fcee9c.pdf
Journal of Heat and Mass Transfer Research(JHMTR)
JHMTR
2345-508X
2345-508X
2014
1
1
Effect of magnetic field on the boundary layer flow, heat, and mass transfer of nanofluids over a stretching cylinder
Aminreza
Noghrehabadi
Mohammad
Ghalambaz
Ehsan
Izadpanahi
Rashid
Pourrajab
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
2014
05
01
9
16
http://jhmtr.journals.semnan.ac.ir/article_149_9aad9d7574b00a925fec3f564a023ce6.pdf
Journal of Heat and Mass Transfer Research(JHMTR)
JHMTR
2345-508X
2345-508X
2014
1
1
An experimental investigation of rheological characteristics of non- Newtonian nanofluids
Milad
Tajik Jamal-Abad
Maziar
Dehghan
Seyfolah
Saedodin
Mohammad Sadegh
Valipour
Amirhossein
Zamzamian
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
2014
05
01
17
23
http://jhmtr.journals.semnan.ac.ir/article_150_401305767c71cb6aabc76faa75d3c22e.pdf
Journal of Heat and Mass Transfer Research(JHMTR)
JHMTR
2345-508X
2345-508X
2014
1
1
Entropy generation calculation for laminar fully developed forced flow and heat transfer of nanofluids inside annuli
Roohollah
Rafee
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
2014
05
01
25
33
http://jhmtr.journals.semnan.ac.ir/article_151_c39cb6485723d5489b60e3a2272e7cff.pdf
Journal of Heat and Mass Transfer Research(JHMTR)
JHMTR
2345-508X
2345-508X
2014
1
1
The optimization of inlet and outlet port locations of a vented square cavity
Taher
Armaghani
Farhad
Talebi
Amir Houshang
Mahmoudi
M
Farzaneh Gord
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
2014
05
01
35
45
http://jhmtr.journals.semnan.ac.ir/article_152_927bdd54aeb26a6e0a5e77b1b39891af.pdf
Journal of Heat and Mass Transfer Research(JHMTR)
JHMTR
2345-508X
2345-508X
2014
1
1
Experimental investigation and proposed correlations for temperaturedependent thermal conductivity enhancement of ethylene glycol based nanofluid containing ZnO nanoparticles
Mohammad
Hemmat Esfe
Seyfolah
Saedodin
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
2014
05
01
47
54
http://jhmtr.journals.semnan.ac.ir/article_153_9251c831bba6699048c766e91d9145a4.pdf
Journal of Heat and Mass Transfer Research(JHMTR)
JHMTR
2345-508X
2345-508X
2014
1
1
Boundary layer flow beneath a uniform free stream permeable continuous moving surface in a nanofluid
Ioan
Pop
Sarkhosh
Seddighi
Norfifah
Bachok
Fudziah
Ismail
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
2014
05
01
55
65
http://jhmtr.journals.semnan.ac.ir/article_154_e40cc08957afcb290a5aeb7185e67c89.pdf