scholarly journals Numerical Study on Natural Convection of Alumina-water Nanofluid in a Square Cavity with Two Localized Heat Sources on Adjacent Surfaces

2021 ◽  
Author(s):  
Farooq Shaik ◽  
Vinay Kumar Domakonda
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Natural Convection ◽  
Vertical Velocity ◽  
Volume Fraction ◽  
Numerical Study ◽  
Al2o3 Nanoparticles ◽  
Heat Sources ◽  
Square Cavity ◽  
The Impact

In the present work, results of a numerical study carried out using finite volume method, to investigate the fluid flow and heat transfer characteristics of Alumina ( Al2O3 ) nanoparticles in the base fluid (water) in a square cavity under natural convection mode are presented. The Semi Implicit Method for Pressure Linked Equations (SIMPLE) algorithm was used to solve the discretized momentum and energy equations. Constant temperature heat sources of same strength are placed on bottom and left vertical surfaces whereas the right surface was kept cold, while the top surface was maintained as adiabatic. The impact of Rayleigh number (RaN) ( 1000 to 106 ) and nanoparticles volume fraction (Φ = 0 %, 5 %, 10 %, 15 % and 20 %) on fluid and heat flow characteristics were numerically investigated and presented in the form of streamlines, isothermal lines, mid line horizontal and vertical velocity components, local Nusselt number ( Nuloc ) and average Nusselt number ( Nuavg ). The obtained results indicate, for lower RaN ( i.e; 103 ), conduction dominates over convection near heated surfaces and results in lower fluid velocities and poor heat transfer. For higher values of RaN ( RaN = 105 and 106 ) and volume fraction of nanoparticles, there was a significant increase in mid horizontal and vertical velocity components, Nuloc and Nuavg due to increase in convective heat transfer and thermal conductivity of nanofluid.

scholarly journals Effect of Al2O3 Nanoparticles and Cylindrical Pins on Natural Convection Heat Transfer in a C-Shaped Enclosure

2020 ◽  
Vol 12 (4) ◽  
pp. 499-515
Author(s):  
M. Y. Arafat ◽  
F. Faisal
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Natural Convection ◽  
Rayleigh Number ◽  
Average Nusselt Number ◽  
Volume Fraction ◽  
Numerical Study ◽  
Convection Heat Transfer ◽  
Al2o3 Nanoparticles ◽  
Simpler Algorithm

A numerical study has been conducted to investigate the transport mechanism of natural convection in a C-shaped enclosure filled with water-Al2O3 nanofluid for various pertinent parameters. The effects of the volume fraction of the Al2O3 nanoparticles, Rayleigh number, and radius of inserted cylindrical pins on the temperature, velocity, heat flux profiles and average Nusselt number have been investigated. General correlations for the effective thermal conductivity and viscosity of nanofluids are used for this analysis. The governing mass, momentum and energy equations are solved numerically with the finite volume method using the SIMPLER algorithm. The results show that addition of nanoparticle improves the heat transfer performance. Insertion of cylindrical pins of lower radius increases the average Nusselt number irrespective of Rayleigh number. But anomaly has been observed while pins of higher radius are inserted due to enormous disturbance in the fluid.

scholarly journals Effect of radiation on the flow structure and heat transfer in a 2-D gray medium

2019 ◽  
Vol 23 (6 Part A) ◽  
pp. 3603-3614
Author(s):  
Nesrine Rachedi ◽  
Madiha Bouafia ◽  
Messaoud Guellal ◽  
Saber Hamimid
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Natural Convection ◽  
Average Nusselt Number ◽  
Radiative Transfer Equation ◽  
Numerical Study ◽  
Discrete Ordinates ◽  
Square Cavity ◽  
Discrete Ordinates Method ◽  
Gray Medium

A numerical study of combined natural convection and radiation in a square cavity filled with a gray non-scattering semi-transparent fluid is conducted. The horizontal walls are adiabatic and the vertical are differentially heated. Convection is treated by the finite volumes approach and the discrete ordinates method is used to solve radiative transfer equation using S6 order of angular quadrature. Representative results illustrating the effects of the Rayleigh number, the optical thickness and the Planck number on the flow and temperature distribution are reported. In addition, the results in terms of the average Nusselt number obtained for various parametric conditions show that radiation modifies significantly the thermal behavior of the fluid within the enclosure.

Numerical Simulation of Heat Transfer in Laminar Natural Convection of Mixed Newtonian-Non-Newtonian and Pure Non-Newtonian Nanofluids in a Square Enclosure

2021 ◽  
pp. 1-44
Author(s):  
Ajay Vallabh ◽  
P.S. Ghoshdastidar
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Base Fluid ◽  
Volume Fraction ◽  
Numerical Study ◽  
Transfer Model ◽  
Nanoparticle Concentration ◽  
Left Wall ◽  
Square Enclosure ◽  
First Case

Abstract This paper presents a steady-state heat transfer model for the natural convection of mixed Newtonian-Non-Newtonian (Alumina-Water) and pure Non-Newtonian (Alumina-0.5 wt% Carboxymethyl Cellulose (CMC)/Water) nanofluids in a square enclosure with adiabatic horizontal walls and isothermal vertical walls, the left wall being hot and the right wall cold. In the first case the nanofluid changes its Newtonian character to Non-Newtonian past 2.78% volume fraction of the nanoparticles. In the second case the base fluid itself is Non-Newtonian and the nanofluid behaves as a pure Non-Newtonian fluid. The power-law viscosity model has been adopted for the non-Newtonian nanofluids. A finite-difference based numerical study with the Stream function-Vorticity-Temperature formulation has been carried out. The homogeneous flow model has been used for modelling the nanofluids. The present results have been extensively validated with earlier works. In Case I the results indicate that Alumina-Water nanofluid shows 4% enhancement in heat transfer at 2.78% nanoparticle concentration. Following that there is a sharp decline in heat transfer with respect to that in base fluid for nanoparticle volume fractions equal to and greater than 3%. In Case II Alumina-CMC/Water nanofluid shows 17% deterioration in heat transfer with respect to that in base fluid at 1.5% nanoparticle concentration. An enhancement in heat transfer is observed for increase in hot wall temperature at a fixed volume fraction of nanoparticles, for both types of nanofluid.

Effect of Periodicity of Non-Uniform Sinusoidal Side Heating on Natural Convection in an Anisotropic Porous-Enclosure

2011 ◽  
Vol 110-116 ◽  
pp. 1613-1618 ◽  
Author(s):  
S. Kapoor ◽  
P. Bera
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Natural Convection ◽  
Stream Function ◽  
Numerical Study ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Maximum Heat ◽  
Maximum Heat Transfer ◽  
Porous Enclosure

A comprehensive numerical study on the natural convection in a hydrodynamically anisotropic as well as isotropic porous enclosure is presented, flow is induced by non uniform sinusoidal heating of the right wall of the enclosure. The principal directions of the permeability tensor has been taken oblique to the gravity vector. The spectral Element method has been adopted to solve numerically the governing differential equations by using the vorticity-stream-function approach. The results are presented in terms of stream function, temperature profile and Nusselt number. The result show that the maximum heat transfer takes place at y = 1.5 when N is odd.. Also, increasing media permeability, by changing K* = 1 to K* = 0.2, increases heat transfer rate at below and above right corner of the enclosure. Furthermore, for the all values of N, profiles of local Nusselt number (Nuy) in isotropic as well as anisotropic media are similar, but for even values of N differ slightly at N = 2.. In particular the present analysis shows that, different periodicity (N) of temperature boundary condition has the significant effect on the flow pattern and consequently on the local heat transfer phenomena.

scholarly journals Natural convection in a differentially heated enclosure with triangular roof

1970 ◽  
Vol 39 (1) ◽  
pp. 1-7 ◽  
Author(s):  
Sumon Saha ◽  
Noman Hasan ◽  
Chowdhury Md Feroz
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Fluid Flow ◽  
Natural Convection ◽  
Average Nusselt Number ◽  
Numerical Study ◽  
Convection Heat Transfer ◽  
Element Analysis ◽  
Left Wall ◽  
Square Enclosure

A numerical study has been carried out for laminar natural convection heat transfer within a two-dimensional modified square enclosure having a triangular roof. The vertical sidewalls are differentially heated considering a constant flux heat source strip is flush mounted with the left wall. The opposite wall is considered isothermal having a temperature of the surrounding fluid. The rest of the walls are adiabatic. Air is considered as the fluid inside the enclosure. The solution has been carried out on the basis of finite element analysis by a non-linear parametric solver to examine the heat transfer and fluid flow characteristics. Different heights of the triangular roof have been considered for the present analysis. Fluid flow fields and isotherm patterns and the average Nusselt number are presented for the Rayleigh numbers ranging from 103 to 106 in order to show the effects of these governing parameters. The average Nusselt number computed for the case of isoflux heating is also compared with the case of isothermal heating as available in the literature. The outcome of the present investigation shows that the convective phenomenon is greatly influenced by the inclined roof height. Keywords: Natural convection, triangular roof, Rayleigh number, isoflux heating. Doi:10.3329/jme.v39i1.1826 Journal of Mechanical Engineering, vol. ME39, No. 1, June 2008 1-7

scholarly journals Numerical study of the turbulent natural convection of nanofluids in a partially heated cubic cavity

2021 ◽  
pp. 57-57
Author(s):  
Zakaria Lafdaili ◽  
Sakina El-Hamdani ◽  
Abdelaziz Bendou ◽  
Karim Limam ◽  
Bara El-Hafad
Keyword(s):  
Nusselt Number ◽  
Natural Convection ◽  
Heat Exchange ◽  
Metallic Nanoparticles ◽  
Volume Fraction ◽  
Numerical Study ◽  
Three Dimensional ◽  
Stability Characteristic ◽  
Horizontal Strip ◽  
Turbulent Natural Convection

In this work we study numerically the three-dimensional turbulent natural convection in a partially heated cubic cavity filled with water containing metallic nanoparticles, metallic oxides and others based on carbon.The objective is to study and compare the effect of the addition of nanoparticles studied in water and also the effect of the position of the heated partition on the heat exchange by turbulent natural convection in this type of geometry, which can significantly improve the design of heat exchange systems for better space optimization. For this we have treated numerically for different volume fractions the turbulent natural convection in the two cases where the cavity is heated respectively by a vertical and horizontal strip in the middle of one of the vertical walls. To take into account the effects of turbulence, we used the standard turbulence model ? - ?. The governing equations are discretized by the finite volume method using the power law scheme which offers a good stability characteristic in this type of flow. The results are presented in the form of isothermal lines and current lines. The variation of the mean Nusselt number is calculated for the two positions of the heated partition as a function of the volume fraction of the nanoparticles studied in water for different Rayleigh numbers.The results show that carbon-based nanoparticles intensify heat exchange by convection better and that the position of the heated partition significantly influences heat exchange by natural convection. In fact, an improvement in the average Nusselt number of more than 20% is observed for the case where the heated partition is horizontal.

scholarly journals Effects of a Rotating Cone on the Mixed Convection in a Double Lid-Driven 3D Porous Trapezoidal Nanofluid Filled Cavity under the Impact of Magnetic Field

Nanomaterials ◽  
2020 ◽  
Vol 10 (3) ◽  
pp. 449 ◽  
Author(s):  
Ali J. Chamkha ◽  
Fatih Selimefendigil ◽  
Hakan F. Oztop
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Nusselt Number ◽  
Aspect Ratio ◽  
Mixed Convection ◽  
Average Nusselt Number ◽  
Volume Fraction ◽  
Rotational Velocity ◽  
Rotating Cone ◽  
The Impact

Effects of a rotating cone in 3D mixed convection of CNT-water nanofluid in a double lid-driven porous trapezoidal cavity is numerically studied considering magnetic field effects. The numerical simulations are performed by using the finite element method. Impacts of Richardson number (between 0.05 and 50), angular rotational velocity of the cone (between −300 and 300), Hartmann number (between 0 and 50), Darcy number (between 10 − 4 and 5 × 10 − 2 ), aspect ratio of the cone (between 0.25 and 2.5), horizontal location of the cone (between 0.35 H and 0.65 H) and solid particle volume fraction (between 0 and 0.004) on the convective heat transfer performance was studied. It was observed that the average Nusselt number rises with higher Richardson numbers for stationary cone while the effect is reverse for when the cone is rotating in clockwise direction at the highest supped. Higher discrepancies between the average Nusselt number is obtained for 2D cylinder and 3D cylinder configuration which is 28.5% at the highest rotational speed. Even though there are very slight variations between the average Nu values for 3D cylinder and 3D cone case, there are significant variations in the local variation of the average Nusselt number. Higher enhancements in the average Nusselt number are achieved with CNT particles even though the magnetic field reduced the convection and the value is 84.3% at the highest strength of magnetic field. Increasing the permeability resulted in higher local and average heat transfer rates for the 3D porous cavity. In this study, the aspect ratio of the cone was found to be an excellent tool for heat transfer enhancement while 95% enhancements in the average Nusselt number were obtained. The horizontal location of the cone was found to have slight effects on the Nusselt number variations.

CFD Investigation of Al2O3 Nanoparticles Effect on Heat Transfer Enhancement of Newtonian and Non-Newtonian Fluids in a Helical Coil

2019 ◽  
Vol 14 (3) ◽  
Author(s):  
Javad Aminian Dehkordi ◽  
Arezou Jafari
Keyword(s):  
Heat Transfer ◽  
Aqueous Solution ◽  
Nusselt Number ◽  
Base Fluid ◽  
Volume Fraction ◽  
Reynolds Numbers ◽  
Helical Coil ◽  
Al2o3 Nanoparticles ◽  
Nanoparticles Volume Fraction ◽  
Computational Fluid Dynamics Cfd

Abstract The present study applied computational fluid dynamics (CFD) to investigate the heat transfer of Newtonian (water) and non-Newtonian (0.3 %wt. aqueous solution of carboxymethylcellulose (CMC)) fluids in the presence of Al2O3 nanoparticles. To analyze the heat transfer rate, investigations were performed in a vertical helical coil as essential heat transfer equipment, at different inlet Reynolds numbers. To verify the accuracy of the simulation model, experimental data reported in the literature were employed. Comparisons showed the validity of simulation results. From the results, compared to the aqueous solution of CMC, water had a higher Nusselt number. In addition, it was observed that adding nanoparticles to a base fluid presented different results in which water/Al2O3 nanofluid with nanoparticles’ volume fraction of 5 % was more effective than the same base fluid with a volume fraction of 10 %. In lower ranges of Reynolds number, adding nanoparticles was more effective. For CMC solution (10 %), increasing concentration of nanoparticles caused an increase in the apparent viscosity. Consequently, the Nusselt number was reduced. The findings reveal the important role of fluid type and nanoparticle concentration in the design and development of heat transfer equipment.

Three-Dimensional Steady and Oscillatory Natural Convection in a Rectangular Enclosure With Heat Sources

2016 ◽  
Vol 138 (9) ◽  
Author(s):  
Amin Bouraoui ◽  
Rachid Bessaïh
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Numerical Study ◽  
Three Dimensional ◽  
Air Cooling ◽  
Heat Sources ◽  
Rectangular Enclosure ◽  
Aspect Ratios ◽  
Simpler Algorithm ◽  
Strong Relation

In this paper, a numerical study of three-dimensional (3D) natural convection air-cooling of two identical heat sources, simulating electronic components, mounted in a rectangular enclosure was carried out. The governing equations were solved by using the finite-volume method based on the SIMPLER algorithm. The effects of Rayleigh number Ra, spacing between heat sources d, and aspect ratios Ax in x-direction (horizontal) and Az in z-direction (transversal) of the enclosure on heat transfer were investigated. In steady state, when d is increased, the heat transfer is more important than when the aspect ratios Ax and Az are reduced. In oscillatory state, the critical Rayleigh numbers Racr for different values of spacing between heat sources and their aspect ratios, at which the flow becomes time dependent, were obtained. Results show a strong relation between heat transfers, buoyant flow, and boundary layer. In addition, the heat transfer is more important at the edge of each face of heat sources than at the center region.

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