2021-10-24T23:02:00Z
https://chal.usb.ac.ir/?_action=export&rf=summon&issue=178
Challenges in Nano and Micro Scale Science and Technology
CNMST
2322-3634
2322-3634
2013
1
1
Natural Convection and Entropy Generation in Γ-Shaped Enclosure Using Lattice Boltzmann Method
E.
Fattahi
M.
Farhadi
K.
Sedighi
This work presents a numerical analysis of entropy generation in Γ-Shaped enclosure that was submitted to the natural convection process using a simple thermal lattice Boltzmann method (TLBM) with the Boussinesq approximation. A 2D thermal lattice Boltzmann method with 9 velocities, D2Q9, is used to solve the thermal flow problem. The simulations are performed at a constant Prandtl number (Pr = 0.71) and Rayleigh numbers ranging from 103 to 106 at the macroscopic scale (Kn = 10-4). In every case, an appropriate value of the characteristic velocity is chosen using a simple model based on the kinetic theory. By considering the obtained dimensionless velocity and temperature values, the distributions of entropy generation due to heat transfer and fluid friction are determined. It is found that for an enclosure with high value of Rayleigh number (i.e., Ra=105), the total entropy generation due to fluid friction and total Nu number increases with decreasing the aspect ratio.
Entropy generation
Lattice Boltzmann Method
natural convection
Γ-Shaped enclosure
2013
01
01
1
18
https://chal.usb.ac.ir/article_991_ed33fb88310481a59b7edd67542621f9.pdf
Challenges in Nano and Micro Scale Science and Technology
CNMST
2322-3634
2322-3634
2013
1
1
Modeling of Activated Carbon Preparation from Spanish Anthracite Based on ANFIS Structure
S.
Rashidi
M.A.
Fanaei
A.
Ahmadpour
Carbon nanostructures are famous structures which are used in several industries such as separation, treatment, energy storage (i.e. methane and hydrogen storage), etc. A successful modeling of activated carbon preparation is very important in saving time and money. There are some attempts to achieve the appropriate theoretical modeling of activated carbon preparation but most of them were almost unsuccessful due to the complexity between the input and output variables. In this paper the empirical modeling of activated carbon preparation from Spanish anthracite based on adaptive neuro-fuzzy inference system (ANFIS) is investigated. ANFIS model is established to delineate the relationship between the BET surface area of the prepared activated carbon with initial and operational conditions; agent type, agent ratio, activation temperature, activation time and nitrogen flow. The results show that the selected model have a good accuracy with a coefficient of determination values (R2) of 0.9885 and average relative error (ARE) of 0.00268.
Activated Carbon
ANFIS
Carbon nanostructure
Neural Network
2013
01
01
19
25
https://chal.usb.ac.ir/article_992_1e5844e35c4560564226b256369531cd.pdf
Challenges in Nano and Micro Scale Science and Technology
CNMST
2322-3634
2322-3634
2013
1
1
Numerical Study of Mixed Convection of Nanofluid in a Concentric Annulus with Rotating Inner Cylinder
G. A.
Sheikhzadeh
H.
Teimouri
M.
Mahmoodi
In this work, the steady and laminar mixed convection of nanofluid in horizontal concentric annulus withrotating inner cylinder is investigated numerically. The inner and outer cylinders are kept at constanttemperature Ti and To respectively, where Ti>To. The annular space is filled with Alumina-water nanofluid.The governing equations with the corresponded boundary conditions in the polar coordinate are discretizedusing the ﬁnite volume method where pressure-velocity coupling is done by the SIMPLER algorithm.Numerical results have been obtained for Rayleigh number ranging from 102 to 105, Reynolds number from 1 to 300 and nanoparticles volume fraction from 0.01 to 0.06. The effects of the Reynolds and Rayleigh numbers, average diameter of nanoparticles and the volume fraction of the nanoparticles on the fluid flow and heat transfer inside the annuli are investigated. According to the results, the average Nusselt number decreases with increasing the Reynolds number. However, the average Nusselt number increases by increasing the Rayleigh number. Moreover, the maximum average Nusselt number occurs for an optimal nanoparticle volume fraction except situations that heat conduction predominates over the heat convection. In these conditions the average Nusselt number is close to unity.
Concentric Annulus
Finite Volume Method
Mixed convection
Nanofluid
Rotating Inner Cylinder
2013
01
01
26
36
https://chal.usb.ac.ir/article_993_6b72c034dcb4abb14c68e9aaea3b1951.pdf
Challenges in Nano and Micro Scale Science and Technology
CNMST
2322-3634
2322-3634
2013
1
1
Numerical Analysis of Inlet Gas-Mixture Flow Rate Effects on Carbon Nanotube Growth Rate
B.
Zahed
T.
Fanaei S.
H.
Ateshi
The growth rate and uniformity of Carbon Nano Tubes (CNTs) based on Chemical Vapor Deposition (CVD) technique is investigated by using a numerical model. In this reactor, inlet gas mixture, including xylene as carbon source and mixture of argon and hydrogen as carrier gas enters into a horizontal CVD reactor at atmospheric pressure. Based on the gas phase and surface reactions, released carbon atoms are grown as CNTs on the iron catalysts at the reactor hot walls. The effect of inlet gas-mixture flow rate, on CNTs growth rate and its uniformity is discussed. In addition the velocity and temperature profile and also species concentrations throughout the reactor are presented.
Chemical Vapor Deposition
Numerical Analysis
Carbon Nanotube
2013
01
01
37
44
https://chal.usb.ac.ir/article_994_52a54eb2f90863cb821e6c9896191495.pdf
Challenges in Nano and Micro Scale Science and Technology
CNMST
2322-3634
2322-3634
2013
1
1
Preparation of γ-Al2O3 and Prioritization of Affecting Factors on the Crystallite Size Using Taguchi Method
M.
Shayesteh
M.
Shafiee Afarani
A.
Samimi
M.
Khorram
In this work, boehmite sol was prepared by a previously applied and validated method; hydrolysis of aluminum chloride hexa-hydrate. In order to obtain precise results, the effect of pH after adding precipitating agent, aging time, peptizing temperature and ultrasonic vibration time on the crystallite size of final precipitate were investigated in a narrow range. The preparation conditions applied in the production step of nanocrystalline boehmite affected on the desired alumina phase. Experiments were set based on the statistical design of experiments (Taguchi method). Furthermore the influence of calcination on crystallization and phase transformation of the precipitate was investigated using X-ray diffractometry (XRD) and simultaneous thermal analysis (STA) techniques. To evaluate the results, the obtained data were statistically analyzed. Considering the statisti cal analysis of experiments, the pH after adding precipitating agent is the major parameter affecting crystallite size. In contrast, aging time has the smallest effect on the crystallite size. In addition, Transmission electron microscopy (TEM) of the samples revealed that the particle size of the powders was well distributed in the nano-size range. Taguchi prediction on the crystallite size was 2.096±0.139 nm (with confidence interval of 95%) which confirmed by a verification experiment (2.064 nm).
Boehmite
γ-alumina
Precipitation
aging time
ultrasonic vibration
Experimental design
2013
01
01
45
52
https://chal.usb.ac.ir/article_995_e336e2525dd3abae3cac0ffda37cb23a.pdf
Challenges in Nano and Micro Scale Science and Technology
CNMST
2322-3634
2322-3634
2013
1
1
Study on Thermal and Hydrodynamic Indexes of a Nanofluid Flow in a Micro Heat Sink
M.
Izadi
M. M.
Shahmardan
A. M.
Rashidi
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.
Microchannel heat sink
Nanofluid
Viscous dissipation effect
2013
01
01
53
63
https://chal.usb.ac.ir/article_996_bc15214e1358cf5ff5b5df0d67140891.pdf
Challenges in Nano and Micro Scale Science and Technology
CNMST
2322-3634
2322-3634
2013
1
1
Investigation of the Effect of Nanoparticles Mean Diameter on Turbulent Mixed Convection of a Nanofluid in a Horizontal Curved tube Using a Two Phase Approach
O.
Ghaffari
A.
Behzadmehr
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.
Nanofluid
Turbulent Mixed Convection
Two phase
Curved tube
nanoparticles mean diameter
Pressure drop
2013
01
01
64
74
https://chal.usb.ac.ir/article_997_d472c32290701d713a0453f8ff4f880f.pdf