scholarly journals Analysis of Heat Transfer in a Triangular Enclosure Filled with a Porous Medium Saturated with Magnetized Nanofluid Charged by an Exothermic Chemical Reaction

2019 ◽  
Vol 2019 ◽  
pp. 1-19
Author(s):  
Raees-ul-Haq Muhammad
Keyword(s):  
Heat Transfer ◽  
Chemical Reaction ◽  
Volume Fraction ◽  
Physical Phenomenon ◽  
Convection Heat Transfer ◽  
Numerical Procedure ◽  
Boussinesq Approximation ◽  
Brownian Diffusion ◽  
Model Parameters ◽  
Exothermic Chemical Reaction

This paper intends to numerically study the steady-state free convection heat transfer in the presence of an exothermal chemical reaction governed by Arrhenius kinetics within a right-angled enclosure of triangular shape filled by porous media saturated with magnetized nanofluid. An approximation named as Darcy–Boussinesq approximation along with a nanofluid model mathematically propounded by Buongiorno has been implemented to model physical phenomenon representing fluid flow, heat transfer, and nanoparticle concentration. The mathematical equations in a dimensionless form describing the stream function for circulation of the fluid, the energy equation for heat, and nanoparticle volume fraction for concentration are solved using the finite difference method. The validity of the numerical procedure is established by comparing present results with the formerly available works in both statistical and graphical approaches. Streamlines, isotherms, and isoconcentrations are plotted and discussed for the various parametric regimes. The graphical description depicts that the average Nusselt and Sherwood numbers are the decreasing function of the Rayleigh number. The study revealed the accountable influence of model parameters such as thermophoresis and Brownian diffusion on the local Sherwood number, whereas a minimum impact on the local Nusselt number is observed.

scholarly journals Numerical investigation of nanoparticles slip mechanisms impact on the natural convection heat transfer characteristics of nanofluids in an enclosure

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Muritala Alade Amidu ◽  
Yacine Addad ◽  
Mohamed Kamel Riahi ◽  
Eiyad Abu-Nada
Keyword(s):  
Heat Transfer ◽  
Rayleigh Number ◽  
Volume Fraction ◽  
Full Range ◽  
Convection Heat Transfer ◽  
Phase Model ◽  
Brownian Diffusion ◽  
Two Phase ◽  
Great Satisfaction ◽  
Drift Flux

AbstractThis study intends to give qualitative results toward the understanding of different slip mechanisms impact on the natural heat transfer performance of nanofluids. The slip mechanisms considered in this study are Brownian diffusion, thermophoretic diffusion, and sedimentation. This study compares three different Eulerian nanofluid models; Single-phase, two-phase, and a third model that consists of incorporating the three slip mechanisms in a two-phase drift-flux. These slip mechanisms are found to have different impacts depending on the nanoparticle concentration, where this effect ranges from negligible to dominant. It has been reported experimentally in the literature that, with high nanoparticle volume fraction the heat transfer deteriorates. Admittingly, classical nanofluid models are known to underpredict this impairment. To address this discrepancy, this study focuses on the effect of thermophoretic diffusion and sedimentation outcome as these two mechanisms turn out to be influencing players in the resulting heat transfer rate using the two-phase model. In particular, the necessity to account for the sedimentation contribution toward qualitative modeling of the heat transfer is highlighted. To this end, correlations relating the thermophoretic and sedimentation coefficients to the nanofluid concentration and Rayleigh number are proposed in this study. Numerical experiments are presented to show the effectiveness of the proposed two-phase model in approaching the experimental data, for the full range of Rayleigh number in the laminar flow regime and for nanoparticles concentration of (0% to 3%), with great satisfaction.

scholarly journals Heat transfer enhancement in the complex geometries filled with porous media

2019 ◽  
pp. 166-166 ◽  
Author(s):  
Zeinab Rashed ◽  
Sameh Ahmed ◽  
Abdelraheem Aly
Keyword(s):  
Heat Transfer ◽  
Porous Medium ◽  
Volume Fraction ◽  
Convection Heat Transfer ◽  
Boussinesq Approximation ◽  
Complex Geometries ◽  
Enhancing Heat Transfer ◽  
Nanoparticles Volume Fraction ◽  
Vertical Walls ◽  
Wavy Cavity

The present numerical investigation aims to analysis the enhancement heat transfer in the nanofluid filled-complex geometries saturated with a partially layered porous medium. The vertical walls of the cavity are taken as complex wavy geometries. The horizontal walls of the cavity are flat with insulated temperature. The complex wavy cavity is filled with a nanofluid and the upper half of the wavy cavity is saturated with the porous medium. In the analysis, the governing equations are formulated for natural convection under the Boussinesq approximation in various environments including pure-fluid, nanofluid, and porous medium. In this investigation, the effects of the Rayleigh number (103?Ra?105), Darcy parameter (10?6? Da ?10?3), thermophoresis parameter (0.1? Nt ?0.5), nanofluid buoyancy ratio (0.1? Nr ?0.5), Brownian motion parameter (0.1?Nb?0.5), inclination angle (0?? ? ?90?), and geometry parameters ?1 and R have been studied on the streamlines, temperature, nanoparticles volume fraction, local Nusselt number Nu and the local Sherwood number Sh. It is found that, the performance of the heat transfer can be improved by adjusting the geometry parameters of the wavy surface. Overall, the results showed that the nanofluid parameters enhance the convection heat transfer and the obtained results provide a useful insight for enhancing heat transfer in two separate layers of nanofluid and porous medium inside complex-wavy cavity.

Effects of Insulated and Isothermal Baffles on Pseudosteady-State Natural Convection Inside Spherical Containers

2010 ◽  
Vol 132 (6) ◽  
Author(s):  
Yuping Duan ◽  
S. F. Hosseinizadeh ◽  
J. M. Khodadadi
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Heat Transfer Enhancement ◽  
Numerical Procedure ◽  
Boussinesq Approximation ◽  
Transfer Enhancement ◽  
Nusselt Numbers ◽  
Extended Surface ◽  
Parametric Studies ◽  
Thermal Layer

The effects of insulated and isothermal thin baffles on pseudosteady-state natural convection within spherical containers were studied computationally. The computations are based on an iterative, finite-volume numerical procedure using primitive dependent variables. Natural convection effect is modeled via the Boussinesq approximation. Parametric studies were performed for a Prandtl number of 0.7. For Rayleigh numbers of 104, 105, 106, and 107, baffles with three lengths positioned at five different locations were investigated (120 cases). The fluid that is heated adjacent to the sphere rises replacing the colder fluid, which sinks downward through the stratified stable thermal layer. For high Ra number cases, the hot fluid at the bottom of the sphere is also observed to rise along the symmetry axis and encounter the sinking colder fluid, thus causing oscillations in the temperature and flow fields. Due to flow obstruction (blockage or confinement) effect of baffles and also because of the extra heating afforded by the isothermal baffle, multi-cell recirculating vortices are observed. This additional heat is directly linked to creation of another recirculating vortex next to the baffle. In effect, hot fluid is directed into the center of the sphere disrupting thermal stratified layers. For the majority of the baffles investigated, the Nusselt numbers were generally lower than the reference cases with no baffle. The extent of heat transfer modification depends on Ra, length, and location of the extended surface. With an insulated baffle, the lowest amount of absorbed heat corresponds to a baffle positioned horizontally. Placing a baffle near the top of the sphere for high Ra number cases can lead to heat transfer enhancement that is linked to disturbance of the thermal boundary layer. With isothermal baffles, heat transfer enhancement is achieved for a baffle placed near the bottom of the sphere due to interaction of the counterclockwise rotating vortex and the stratified layer. For some high Ra cases, strong fluctuations of the flow and thermal fields indicating departure from the pseudosteady-state were observed.

scholarly journals Numerical Analysis of Nanofluids in Differentially Heated Enclosure Undergoing Orthogonal Rotation

2014 ◽  
Vol 2014 ◽  
pp. 1-11 ◽  
Author(s):  
H. Saleh ◽  
I. Hashim
Keyword(s):  
Heat Transfer ◽  
Transfer Rate ◽  
Volume Fraction ◽  
Solid Volume Fraction ◽  
Convection Heat Transfer ◽  
Staggered Grid ◽  
Governing Equations ◽  
Nanoparticles Concentration ◽  
Quantity Of Heat ◽  
Velocity Pressure

Natural convection heat transfer in a rotating, differentially heated enclosure is studied numerically in this paper. The rotating enclosure is filled with water-Ag, water-Cu, water-Al2O3, or water-TiO2nanofluids. The governing equations are in velocity, pressure, and temperature formulation and solved using the staggered grid arrangement together with MAC method. The governing parameters considered are the solid volume fraction,0.0 ≤ ϕ ≤ 0.05, and the rotational speeds,3.5≤ Ω ≤ 17.5 rpm, and the centrifugal force is smaller than the Coriolis force and both forces were kept below the buoyancy force. It is found that the angular locations of the local maximums heat transfer were sensitive to rotational speeds and nanoparticles concentration. The global quantity of heat transfer rate increases about 1.5%, 1.1%, 0.8%, and 0.6% by increasing 1%ϕof the nanoparticles Ag, Cu, Al2O3, and TiO2, respectively, for the considered rotational speeds.

scholarly journals Study of convection heat transfer enhancement inside lid driven cavity utilizing fins and nanofluid

2017 ◽  
Vol 21 (6 Part A) ◽  
pp. 2431-2442
Author(s):  
Arash Lavasani ◽  
Mousa Farhadi ◽  
Darzi Rabienataj
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Richardson Number ◽  
Volume Fraction ◽  
Convection Heat Transfer ◽  
Thermal Conductivity Ratio ◽  
Convection Flow ◽  
Driven Cavity ◽  
Ratio Change ◽  
Hot Surface

In the present study, the effect of suspension of nanoparticle on mixed convection flow is investigated numerically in lid driven cavity with fins on its hot surface. Study is carried out for Richardson numbers ranging from 0.1 to 10, fin(s) height ratio change from 0.05 to 0.15 and volume fraction of nanoparticles from 0 to 0.03, respectively. The thermal conductivity ratio (kfin/kf) is equal to 330 and Grashof number is assumed to be constant (104) so that the Richardson numbers changes with Reynolds number. Results show that the heat transfer enhances by using nanofluid for all studied Richardson numbers. Adding fins on hot wall has different effects on heat transfer depend to Richardson number and height of fins. Use of low height fin in flow with high Richardson number enhances the heat transfer rate while by increasing the height of fin the heat transfer reduces even lower than it for pure fluid. The overall enhancement in Nusselt number by adding 3% nanoparticles and 3 fins is 54% at Ri=10. They cause reduction of Nusselt Number by 25% at Ri=0.1. Higher fins decrease the heat transfer due to blocking fluid at corners of fins.

Influence of Cu-Water and CNT-Water Nanofluid on Natural Convection Heat Transfer in a Triangular Solar Collector

2020 ◽  
Author(s):  
Didarul Ahasan Redwan ◽  
Md. Habibur Rahman ◽  
Hasib Ahmed Prince ◽  
Emdadul Haque Chowdhury ◽  
M. Ruhul Amin
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Rayleigh Number ◽  
Solar Collector ◽  
Average Nusselt Number ◽  
Volume Fraction ◽  
Solid Volume Fraction ◽  
Convection Heat Transfer ◽  
Natural Convection Heat Transfer ◽  
Convection Heat

Abstract A numerical study on natural convection heat transfer in a right triangular solar collector filled with CNT-water and Cuwater nanofluids has been conducted. The inclined wall and the bottom wall of the cavity are maintained at a relatively lower temperature (Tc), and higher temperature (Th), respectively, whereas the vertical wall, is kept adiabatic. The governing non-dimensional partial differential equations are solved by using the Galerkin weighted residual finite element method. The Rayleigh number (Ra) and the solid volume-fraction of nanoparticles (ϕ) are varied in the range of 103 ≤ Ra ≤ 106, and 0 ≤ ϕ ≤ 0.1, respectively, to carry out the parametric simulations within the laminar region. Corresponding thermal and flow fields are presented via isotherms and streamlines. Variations of average Nusselt number as a function of Rayleigh number have been examined for different solid volume-fraction of nanoparticles. It has been found that the natural convection heat transfer becomes stronger with the increment of solid volume fraction and Rayleigh number, but the strength of circulation reduces with increasing nanoparticles’ concentration at low Ra. Conduction mode dominates for lower Ra up to a certain limit of 104. It is also observed that when the solid volume fraction is increased from 0 to 0.1 for a particular Rayleigh number, the average Nusselt number is increased to a great extent, but surprisingly, the rate of increment is more pronounced at lower Ra. Moreover, it is seen that Cu-water nanofluid offers slightly better performance compared to CNT-water but the difference is very little, especially at lower Ra.

Transient Heat Analysis in a Two-Step Radiative Combustible Slab

2021 ◽  
Vol 872 ◽  
pp. 15-19
Author(s):  
Ramoshweu Solomon Lebelo ◽  
Kholeka Constance Moloi
Keyword(s):  
Heat Transfer ◽  
Kinetic Parameters ◽  
Chemical Reaction ◽  
Transfer Rate ◽  
Heat Transfer Analysis ◽  
Shooting Technique ◽  
Surrounding Environment ◽  
Article Analysis ◽  
Exothermic Chemical Reaction ◽  
Rectangular Slab

In this article, analysis of heat transfer in a stockpile of reactive materials modelled in a rectangular slab is carried out. A two-step exothermic chemical reaction is assumed and the heat loss to the surrounding environment is by radiation. The ordinary differential equation (ODE) governing the problem is tackled numerically by Runge-Kutta Fehlberg (RKF45) method coupled with Shooting technique. The heat transfer analysis is simplified by investigation some kinetic parameters’ effects on the temperature of the combusting system. It was found out that some kinetic parameters raise the levels of the temperature by encouraging the exothermic chemical reaction, whereas some, reduce the levels of the temperature to slow down the heat transfer rate. The results are depicted graphically and discussed accordingly.

NATURAL CONVECTION OF ALUMINIUM OXIDE-WATER NANOFLUID

2015 ◽  
Vol 75 (11) ◽  
Author(s):  
A.N. Afifah ◽  
S. Syahrullail ◽  
C.S. Nor Azwadi
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Volume Fraction ◽  
Experimental Studies ◽  
Heating Time ◽  
Brownian Diffusion ◽  
Physical Conditions ◽  
Viscous Solution ◽  
Dispersion Technique ◽  
Increasing Temperature

As suspending nanoparticles in fluid-based give tremendous promise in heat transfer application, an understanding on the mechanism of heat transfer is indispensable. The present study dealt with natural convection of nanofluid inside a square cavity heated at the bottom, while the upper part was exposed to the atmosphere. Experimental studies have been performed for various physical conditions, such as volume fractions of nanoparticles varying from 0% to 2.0%, different dispersion techniques of nanoparticles in fluid-based, and heating time from 0 to 35 minutes. In general, dynamic viscosity of nanofluid clearly increased with volume fraction, but decreased with the increasing temperature. It was found that improper dispersion technique resulted in viscous solution. On top of that, transport mechanism of thermophoresis and Brownian diffusion were considered in analysing heat transfer across the cavity.

The impacts of non-uniform magnetic field on free convection heat transfer of a magnetizable micropolar nanofluid

2019 ◽  
Vol 29 (10) ◽  
pp. 3685-3706
Author(s):  
Zafar Namazian ◽  
S.A.M. Mehryan
Keyword(s):  
Heat Transfer ◽  
Free Convection ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Volume Fraction ◽  
Convection Heat Transfer ◽  
Content Type ◽  
Viscosity Parameter ◽  
Micropolar Nanofluid ◽  
Free Convection Heat

Purpose The purpose of this study is to numerically study the heat transfer of free convection of a magnetizable micropolar nanofluid inside a semicircular enclosure. Design/methodology/approach The flow domain is under simultaneous influences of two non-uniform magnetic fields generated by current carrying wires. The directions of the currents are the same. Although the geometry is symmetric, it is physically asymmetric. The impacts of key parameters, including Rayleigh number Ra = 103-106, Hartman number Ha = 0-50, vortex viscosity parameter Δ = 0-4, nanoparticles volume fraction φ = 0-0.04 and magnetic number Mnf = 0-1000, on the macro- and micro-scales flows, temperature and heat transfer rate are studied. Finding The outcomes show that dispersing of the nanoparticles in the host fluid increases the strength of macro- and micro-scale flows. When Mnf = 0, the increment of the vortex viscosity parameter increases the strength of the particles micro-rotations, while this characteristic is decreased by growing Δ for Mnf ≠ 0. The increment of Δ and Ha decreases the rate of heat transfer. The increment of Ha decreases the enhancement percentage of heat transfer rate because of dispersing nanoparticles, known as En parameter. In addition, the value of Δ has no effect on En. Moreover, the average Nusselt number Nuavg and En remain constant by increasing the magnetic number Mnf for different volume fraction values. Originality/value The authors believe that all of the results, both numerical and asymptotic, are original and have not been published elsewhere yet.

Natural convection heat transfer augmentation in a partially heated and partially cooled square cavity utilizing nanofluids

2009 ◽  
Vol 19 (3/4) ◽  
pp. 411-431 ◽  
Author(s):  
Manab Kumar Das ◽  
Pravin Shridhar Ohal
Keyword(s):  
Heat Transfer ◽  
Volume Fraction ◽  
Solid Volume Fraction ◽  
Convection Heat Transfer ◽  
Square Cavity ◽  
Content Type ◽  
Heat Transfer Augmentation ◽  
Special Cases ◽  
Simplec Algorithm ◽  
Finite Volume Approach

PurposeThe purpose of this paper is to investigate the behaviour of nanofluids numerically inside a partially heated and partially cooled square cavity to gain insight into heat transfer and flow processes induced by a nanofluid.Design/methodology/approachA model is developed to analyze the behaviour of nanofluids taking into account the solid volume fraction χ. The transport equations are solved numerically with finite volume approach using SIMPLEC algorithm.FindingsComparisons with previously published work on the basis of special cases are performed and found to be in excellent agreement. Five different relative positions of the active zones are considered.While circulation depend strongly on the total exit length. Governing parameters were 103 < Gr < 107 but due to space constraints the results for 104 < Gr <107 are presented. It is found that both the Grashof number and solid volume fraction χ affect the fluid flow and heat transfer in the cavity. CopperWater nanofluid is used with Pr = 6.2 and solid volume fraction is varied as 0, 4, 8, 12, 16 and 20 per cent. Detailed results are presented for flow pattern and heat transfer curves.Originality/valueThe present study focusses on the analysis of several parameters on the heat transfer characteristics of nanofluids within the enclosure.

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