2019-05-22T05:40:31Z
http://jhmtr.journals.semnan.ac.ir/?_action=export&rf=summon&issue=320
Journal of Heat and Mass Transfer Research
JHMTR
2345-508X
2345-508X
2016
3
2
Instabilities of Thin Viscous Liquid Film Flowing down a Uniformly Heated Inclined Plane
Anandamoy
Mukhopadhyay
Sanghasri
Mukhopadhyay
Asim
Mukhopadhyay
Instabilities of a thin viscous film flowing down a uniformly heated plane are investigated in this study. The heating generates a surface tension gradient that induces thermocapillary stresses on the free surface. Thus, the film is not only influenced by gravity and mean surface tension but also the thermocapillary force is acting on the free surface. Moreover, the heat transfer at the free surface plays a crucial role in the evolution of the film. The main objective of this study is to scrutinize the impact of Biot number Bi which describes heat transfer at the free surface on instability mechanism. Using the long wave expansion method, a generalized non-linear evolution equation of Benney type, including the above mentioned effects, is derived for the development of the free surface. A normal mode approach and the method of multiple scales are used to obtain the linear and weakly nonlinear stability solution for the film flow. The linear stability analysis of the evolution equation shows that the Biot number plays a double role; for Bi < 1 it gives destabilizing effect but for Bi > 1 it produces stabilization. At Bi = 1, the instability is maximum. The weakly nonlinear study reveals that the impact of Marangoni number Mr is very strong on the bifurcation scenario even for its slight variation.<br /> <br />This behaviour of the Biot number is the consequence of the fact that the interfacial<br />temperature is held close to the plane temperature for Bi > 1, thus weakening the Marangoni eﬀect. The weakly nonlinear<br />study reveals that the impact of Marangoni number Mr is very strong on the bifurcation scenario even for its slight variation.
Thin ﬁlm
Marangoni instability
Biot number
2016
10
01
77
87
http://jhmtr.journals.semnan.ac.ir/article_345_a2ad910ba873709bec799c2f994b4f59.pdf
Journal of Heat and Mass Transfer Research
JHMTR
2345-508X
2345-508X
2016
3
2
Numerical Study of Entropy Generation for Natural Convection in Cylindrical Cavities
Abdollah
Rezvani
Mohammad Sadegh
Valipour
Mojtaba
Biglari
In this paper, an enhanced computational code was developed using finite-volume method for solving the incompressible natural convection flow within the cylindrical cavities. Grids were generated by an easy method with a view to computer program providing. An explicit integration algorithm was applied to find the steady state condition. Also instead of the conventional algorithms of SIMPLE, SIMPLEM and SIMPLEC, an artificial compressibility technique is applied for coupling the continuity to the momentum equations. The entropy generation, which is a representation of the irreversibility and efficiency loss in engineering heat transfer processes, has been analyzed in detail. The discretization of the diffusion terms were very simplified using the enhanced scheme similar to the flux averaging in the convective term. Additionally an analysis of the entropy generation in a cylindrical enclosure was performed. In order to show the validation of this study, the code was reproduced to solve similar problem of cited paper. Finally, the solutions were extended for the new cases.
Artificial compressibility
Entropy
Explicit finite-volume method
Natural convection
Nuselt number
2016
10
01
89
99
http://jhmtr.journals.semnan.ac.ir/article_347_78c6fe0a1f9bb42b45e099a3972abb95.pdf
Journal of Heat and Mass Transfer Research
JHMTR
2345-508X
2345-508X
2016
3
2
Flow field and heat transfer in a channel with a permeable wall filled with Al2O3-Cu/water micropolar hybrid nanofluid, effects of chemical reaction and magnetic field
Mahdi
Mollamahdi
Mahmoud
Abbaszadeh
Ghanbar Ali
Sheikhzadeh
In this study, flow field and heat transfer of Al2O3-Cu/water micropolar hybrid nanofluid is investigated in a permeable channel using the least square method. The channel is encountered to chemical reaction, and a constant magnetic field is also applied. The bottom wall is hot and coolant fluid is injected into the channel from the top wall. The effects of different parameters such as the Reynolds number, the Hartmann number, microrotation factor and nanoparticles concentration on flow field and heat transfer are examined. The results show that with increasing the Hartmann number and the Reynolds number, the Nusselt and Sherwood numbers increase. Furthermore, when the hybrid nanofluid is applied rather than pure nanofluid, the heat transfer coefficient will increase significantly. It is also observed that in the case of generative chemical reaction, the fluid concentration is more than the case of destructive chemical reaction. Moreover, the Nusselt number and Sherwood number when the micropolar model is used, is less than when it is not considered.
Micropolar hybrid nanofluid
Magnetic field
Chemical reaction
Channel with a permeable wall
Least square method
2016
10
01
101
114
http://jhmtr.journals.semnan.ac.ir/article_447_e03c5697c1adcf4ec938f270ede758f3.pdf
Journal of Heat and Mass Transfer Research
JHMTR
2345-508X
2345-508X
2016
3
2
A Comparative Solution of Natural Convection in an Open Cavity using Different Boundary Conditions via Lattice Boltzmann Method
Mohsen-Shahrood
Nazari
MH
Kayhani
A Lattice Boltzmann method is applied to demonstrate the comparison results of simulating natural convection in an open end cavity using different hydrodynamic and thermal boundary conditions. The Prandtl number in the present simulation is 0.71, Rayleigh numbers are 104,105 and 106 and viscosities are selected 0.02 and 0.05. On-Grid bounce-back method with first-order accuracy and non-slip method with second-order accuracy are employed for implementation of hydrodynamic boundary conditions. Moreover, two different thermal boundary conditions (with first and second order of accuracy) are also presented for thermal modelling. The results showed that first and second order boundary conditions (thermal/hydrodynamic) are the same for a two-dimensional, single phase, convective heat transfer problem including geometry with straight walls. The obtained results for different hydrodynamic and thermal boundary conditions are useful for the researchers in the field of lattice Boltzmann method in order to implement accurate condition on the boundaries, in different physics.
Lattice Boltzmann method
open cavity
hydrodynamic/Thermal boundary conditions
order of accuracy
2016
10
01
115
129
http://jhmtr.journals.semnan.ac.ir/article_363_45df0d64050eae976a1bfe44dba77d5c.pdf
Journal of Heat and Mass Transfer Research
JHMTR
2345-508X
2345-508X
2016
3
2
Development of a phase change model for volume-of-fluid method in OpenFOAM
Mohammad
Bahreini
Abbas
Ramiar
Ali Akbar
Ranjbar
In this present study, volume of fluid method in OpenFOAM open source CFD package will be extended to consider phase change phenomena with modified model due to condensation and boiling processes. This model is suitable for the case in which both unsaturated phase and saturated phase are present and for beginning boiling and condensation process needn't initial interface. Both phases (liquid-vapor) are incompressible and immiscible. Interface between two phases is tracked with color function volume of fluid (CF-VOF) method. Surface Tension is taken into consideration by Continuous Surface Force (CSF) model. Pressure-Velocity coupling will be solved with PISO algorithm in the collocated grid. The accuracy of this phase-change model is verified by two evaporation problems (a one-dimensional Stefan problem and a two-dimensional film boiling problem) and two condensation problem (a one-dimensional Stefan problem and Filmwise condensation). The simulation results of this model show good agreement with the classical analytical or numerical results, proving its accuracy and feasibility.
Phase change model
Volume-of-fluid
Boiling
Condensation
OpenFOAM
2016
10
01
131
143
http://jhmtr.journals.semnan.ac.ir/article_467_ca58231ab595fe0109fcded9075bdaa4.pdf
Journal of Heat and Mass Transfer Research
JHMTR
2345-508X
2345-508X
2016
3
2
A study of a Stefan problem governed with space–time fractional derivatives
Rajeev
.
M.
Kushwaha
Abhishek
Singh
This paper presents a fractional mathematical model of a one-dimensional phase-change problem (Stefan problem) with a variable latent-heat (a power function of position). This model includes space–time fractional derivatives in the Caputo sense and time-dependent surface-heat flux. An approximate solution of this model is obtained by using the optimal homotopy asymptotic method to find the solutions of temperature distribution in the domain 0 ≤x≤s(t) and interface’s tracking or location. The results thus obtained are compared with existing exact solutions for the case of the integer order derivative at some particular values of the governing parameters. The dependency of movement of the interface on certain parameters is also studied.
Optimal homotopy asymptotic method
Stefan problem
moving interface
fractional derivatives
2016
10
01
145
151
http://jhmtr.journals.semnan.ac.ir/article_384_b95d483f4316662b9bc21735e9582622.pdf
Journal of Heat and Mass Transfer Research
JHMTR
2345-508X
2345-508X
2016
3
2
Analytical and Numerical Studies on Hydromagnetic Flow of Boungiorno Model Nanofluid over a Vertical Plate
A.K. Abdul
Hakeem
B.
Ganga
S. Mohamed
Yusuff Ansari
N.Vishnu
Ganesh
MHD boundary layer flow of two phase model nanofluid over a vertical plate is investigated both analytically and numerically. A system of governing nonlinear partial differential equations is converted into a set of nonlinear ordinary differential equations by suitable similarity transformations and then solved analytically using homotopy analysis method and numerically by the fourth order Runge-Kutta method along with shooting iteration technique. The effects of magnetic parameter, Prandtl number, Lewis number, buoyancy-ratio parameter, Brownian motion parameter and thermophoresis parameter on the velocity profile, temperature profile and concentration profile of the nanofluid are discussed graphically. The values of reduced local Nusselt number and reduced local sherwood number are tabulated and discussed. It is noted that the Brownian motion and thermophoresis parameters enhance the velocity distribution and the temperature distribution, but it suppress the concentration distribution. Furthermore, comparisons have been made with bench mark solutions for a special case and obtained a very good agreement..
Homotopy Analysis Method
MHD
Nanofluid
Runge-Kutta method
Vertical plate
2016
10
01
153
164
http://jhmtr.journals.semnan.ac.ir/article_362_007c90f492d49e570d06968a5e09a8d9.pdf