Effect of Various Tilted Positions of a Thin Fin on Natural Convection of Laminar Viscous Flow in a Square Cavity

An exhaustive numerical investigation is carried out to analyze the role of an isothermal heated thin fin on fluid flow and temperature distribution visualization in an enclosure. Natural convection within square enclosures finds remarkable pragmatic applications. In the present study, a finite difference approach is performed on two-dimensional laminar flow inside an enclosure with cold side walls and adiabatic horizontal walls. The fluid flow equations are reconstructed into vorticity - stream function formulation and these equations are employed utilizing the finite-difference strategy with incremental time steps. The parametric study includes a wide scope of Rayleigh number, Ra, and inclination angle ϴ of the thin fin. The effect of different Rayleigh numbers ranging Ra = 104-106 with Pr=0.71 for all the inclination angles from 0°-360° with uniform rotational length of angle 450 of an inclined heated fin on fluid flow and heat transfer have been investigated. The heat transfer rate within the enclosure is measured by means of local and average Nusselt numbers. Regardless of inclination angles of the thin fin, a slight enhancement in the average Nusselt number is observed when Rayleigh number increased for both the cases of the horizontal and vertical position of the thin fin. When the fin has inclined no change in average Nusselt number is noticed for distinct Rayleigh numbers.

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Free convection of a nanofluid in a square cavity with a heat source on the bottom wall and partially cooled from sides

Thermal Science ◽

10.2298/tsci110406011a ◽

2014 ◽

Vol 18 (suppl.2) ◽

pp. 283-300 ◽

Cited By ~ 7

Author(s):

Mostafa Mahmoodi ◽

Arani Abbasian ◽

Sebdani Mazrouei ◽

Saeed Nazari ◽

Mohammad Akbari

Keyword(s):

Heat Transfer ◽

Nusselt Number ◽

Fluid Flow ◽

Rayleigh Number ◽

Average Nusselt Number ◽

Volume Fraction ◽

Heat Sinks ◽

Square Cavity ◽

Flow And Heat Transfer ◽

Rayleigh Numbers

The problem of free convection fluid flow and heat transfer in a square cavity with a flush mounted heat source on its bottom wall and two heat sinks on its vertical side walls has been investigated numerically. Via changing the location of the heat sinks, six different arrangements have been generated. The cavity was filled with Cu-water nanofluid. The governing equations were discretized using the finite volume method and SIMPLER algorithm. Using the developed code, a parametric study was undertaken, and effects of Rayleigh number, arrangements of the heat sinks and volume fraction of the nanoparticles on fluid flow and heat transfer inside the cavity were investigated. Also for the middle-middle heat sinks arrangement, capability of five different water based nanofluids on enhancement of the rate of heat transfer was examined and compared. From the obtained results it was found that the average Nusselt number, for all six different arrangements of the heat sinks, was an increasing function of the Rayleigh number and the volume fraction of the nanoparticles. Also it was found that at high Rayleigh numbers, maximum and minimum average Nusselt number occurred for middle-middle and top-bottom arrangement, respectively. Moreover it was found that for the middle-middle arrangement, at high Rayleigh numbers, maximum and minimum rate of heat transfer was obtained by Cu-water and TiO2-water nanofluids respectively.

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Numerical Investigation of the Effect of Baffle Inclination Angle on Nanofluid Natural Convection Heat Transfer in A Square Enclosure

Al-Qadisiyah Journal for Engineering Sciences ◽

10.30772/qjes.v12i2.589 ◽

2019 ◽

Vol 12 (2) ◽

pp. 61-71 ◽

Cited By ~ 1

Author(s):

Barik AL-Muhjaa ◽

Khaled Al-Farhany

Keyword(s):

Heat Transfer ◽

Thermal Conductivity ◽

Nusselt Number ◽

Fluid Flow ◽

Natural Convection ◽

Rayleigh Number ◽

Average Nusselt Number ◽

Solid Wall ◽

Convection Heat Transfer ◽

Convection Heat

The characteristics of the conjugate natural convection of (Al2O3-water) nanofluid inside differentially heated enclosure is numerically analyzed using COMSOL Multiphysics (5.3a). The enclosure consists of two vertical walls, the left wall has a thickness and maintain at a uniform hot temperature, while the opposite wall at cold temperature and the horizontal walls are isolated. A high thermal conductivity thin baffle has been added on the insulated bottom wall at a different inclination angles. The effect of the volume fractions of nanoparticles (f), Rayleigh number (Ra), solid wall thermal conductivity ratio (Kr), baffle incline angles (Ø) and the thickness of solid wall (D) on the isothermal lines, fluid flow patterns and the average Nusselt number (Nu) has been investigated. At low Rayleigh number (Ra=103 to 104) the Isothermal lines are parallel with the vertical wall which is characteristic of conduction heat transfer. on the other hand, when Rayleigh number increase to (Ra=106), the isotherms lines distribution in the inner fluid become parallel curves with the adiabatic horizontal walls of the enclosure and smooth in this case convection heat transfer becomes dominant. As the Rayleigh number further increases, the average Nusselt number enhance because of buoyancy force become stronger. In addition, the fluid flow within the space is affected by the presence of a fin attached to the lower wall that causes blockage and obstruction of flow near the hot wall, hence the recirculation cores become weak and effect on the buoyant force. The maximum value of the stream function can be noticed in case of nanofluid at (Ø=60), whereas they decrease when (Ø > 60), where the baffle obstruction causing decreases in flow movement. So that the left region temperature increases which cause reduction of the convective heat transfer by the inner fluid temperatures. This is an indication of enhancing of insulation. When the inclination angle increases (Ø >90), the baffle obstruction on flow and fluid resistance becomes smaller and the buoyancy strength increase, as a result, the heat transfer is increasing in this case. As a result of increasing the thermal conductivity from 1 to 10, an increase in the amount of heat transferred through the solid wall to the internal fluid have been noticed. This change can be seen in the isothermal lines, also, there was growth and an increase in the temperature gradient. The increasing of wall thickness from (D=0.1 to 0.4) leads to reduce the intensive heating through the solid wall as well as small heat transferred to the inner fluid. Therefore, it can be noticed that when the wall thickness increases the stream function decrease.

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Natural convection in a differentially heated enclosure with triangular roof

Journal of Mechanical Engineering ◽

10.3329/jme.v39i1.1826 ◽

1970 ◽

Vol 39 (1) ◽

pp. 1-7 ◽

Cited By ~ 1

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

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ISPH simulations of natural convection from heated rotating paddles on a circular cylinder inside a cross-shaped cavity filled with a nanofluid

10.22541/au.160640288.84638521/v1 ◽

2020 ◽

Author(s):

Abdelraheem Mahmoud Aly ◽

Ehab Mahmoud

Keyword(s):

Heat Transfer ◽

Porous Media ◽

Nusselt Number ◽

Fluid Flow ◽

Natural Convection ◽

Circular Cylinder ◽

Average Nusselt Number ◽

Volume Fraction ◽

Heterogeneous Porous Media ◽

Convection Flow

The numerical simulations of the uniform circular rotation of paddles on circular cylinder results natural convection flow of Al2O3-water in a cross-shaped porous cavity were performed by incompressible representation of smoothed particle hydrodynamics entitled ISPH method. The two vertical area of a cross-shaped cavity is saturated with homogeneous porous media and the whole horizontal area of a cross-shaped cavity is saturated with heterogeneous porous media. The inner paddles on the circular cylinder are rotating around their center by a uniform circular velocity. The whole embedded body of paddles on a circular cylinder has temperature Th. The wall-sides of a cross-shaped cavity are positioned at a temperature Tc. The current geometry can be applied in analysis and understanding the thermophysical behaviors of the electronic motors. The angular velocity is taken as ! = 7:15 and consequently the natural convection case is only considered due to the low speed of inner rotating shape. The performed simulations are represented in the graphical for the temperature distributions, velocity fields and tabular forms for average Nusselt number. The results revealed that an augmentation on paddle length rises the heat transfer and speed of fluid flow inside a cross shaped cavity. Also, an incrementation on Rayleigh number augments the heat transfer and speed of the fluid flow inside a cross-shaped cavity. The fluid flow is circulated only around the rotating inner shape when Darcy parameter decreases to Da = 105. Average Nusselt number Nu enhances by an increment on the paddle lengths and nanoparticles volume fraction

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Prediction of Natural Convection Heat Transfer Phenomena of Nanofluids in Corrugated Annulus

10.21203/rs.3.rs-39325/v1 ◽

2020 ◽

Author(s):

Sattar Aljobair ◽

Akeel Abdullah Mohammed ◽

Israa Alesbe

Keyword(s):

Heat Transfer ◽

Nusselt Number ◽

Natural Convection ◽

Rayleigh Number ◽

Average Nusselt Number ◽

Volume Fraction ◽

Outer Cylinder ◽

Convection Heat Transfer ◽

Natural Convection Heat Transfer ◽

Convection Heat

Abstract The natural convection heat transfer and fluid flow characteristic of water based Al2O3 nano-fluids in a symmetrical and unsymmetrical corrugated annulus enclosure has been studied numerically using CFD. The inner cylinder is heated isothermally while the outer cylinder is kept constant cold temperature. The study includes eight models of corrugated annulus enclosure with constant aspect ratio of 1.5. The governing equations of fluid motion and heat transfer are solved using stream-vorticity formulation in curvilinear coordinates. The range of solid volume fractions of nanoparticles extends from PHI=0 to 0.25, and Rayleigh number varies from 104 to 107. Streamlines, isotherms, local and average Nusselt number of inner and outer cylinder has been investigated in this study. Sixty-four correlations have been deduced for the average Nusselt number for the inner and outer cylinders as a function of Rayleigh number have been deduced for eight models and five values of volume fraction of nano particles with an accuracy range 6-12 %. The results show that, the average heat transfer rate increases significantly as particle volume fraction and Rayleigh number increase. Also, increase the number of undulations in unsymmetrical annuli reduces the heat transfer rates which remain higher than that in symmetrical annuli. There is no remarkable change in isotherms contour with increase of volume fraction of nanofluid.

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Effect of Fin Length and Location on Natural Convection Heat Transfer in a Wavy Cavity

International Journal of Thermofluid Science and Technology ◽

10.36963/ijtst.2020070303 ◽

2020 ◽

Vol 7 (3) ◽

Author(s):

M. Fayz-Al-Asad ◽

M. J. H. Munshi ◽

M.M.A. Sarker

Keyword(s):

Heat Transfer ◽

Nusselt Number ◽

Fluid Flow ◽

Natural Convection ◽

Rayleigh Number ◽

Flow Structure ◽

Model Parameters ◽

Flow And Heat Transfer ◽

Wavy Cavity ◽

Fin Length

The present study aims to analyze the natural convection flow and heat transfer in a wavy cavity with a single horizontal fin attached to its hot wall. Galerkin weighted residual finite element technique has been employed to solve the governing nonlinear dimensionless equations. The effects of model parameters like Rayleigh number, fin length and location on the fluid flow and heat transfer are investigated. The obtained results are exhibited graphically in terms of flow structure, temperature dispersion, velocity field, fin effectiveness, local Nusselt number, and average Nusselt number. It is observed that the different fin length and location have a substantial effect on flow structure and temperature field. Fin effectiveness is also studied and the highest fin effectiveness was found at fin length (L = 0.75). Besides, it is also found that the mean Nusselt number increases significantly with the increase of Rayleigh number and fin length. Wavy cavity becomes more effective on heat transfer behaviors and fluid flow than that of a square cavity.

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Free convection in a tilted triangle porous cavity filled with Cu-water nanofluid with flush mounted heater on the wall

International Journal of Numerical Methods for Heat &amp Fluid Flow ◽

10.1108/hff-10-2011-0226 ◽

2013 ◽

Vol 24 (1) ◽

pp. 2-20 ◽

Cited By ~ 12

Author(s):

Qiang Sun ◽

Ioan Pop

Keyword(s):

Heat Transfer ◽

Nusselt Number ◽

Fluid Flow ◽

Rayleigh Number ◽

Free Convection ◽

Average Nusselt Number ◽

Governing Equations ◽

Content Type ◽

Tilted Angle ◽

Industrial Sectors

Purpose – Steady-state free convection heat transfer and fluid flow of Cu-water nanofluid is investigated within a porous tilted right-angle triangular enclosure. The paper aims to discuss these issues. Design/methodology/approach – The flush mounted heater with finite size is placed on one right-angle wall. The temperature of the inclined wall is lower than the heater, and the rest of walls are adiabatic. The governing equations are obtained based on the Darcy's law, and the nanofluid model adopted is that by Tiwari and Das. The transformed dimensionless governing equations were solved numerically by finite difference method, and the solution for algebraic equations was obtained through successive under relaxation method. Findings – Investigations were made as the tilted angle of the cavity varies within under different values of Rayleigh number for a porous medium with and solid volume fraction parameter of Cu-water nanofluid with. It is found that the maximum value of the average Nusselt number is achieved with the highest Rayleigh number when the tilted angle of the cavity is 150°, while the minimum value of the average Nusselt number is obtained with the lowest Rayleigh number when the tilted angle of the cavity locates at 240°. As soon as the flow convection in the cavity is not significant, increasing can improve the value of, but opposite effects appear when flow convection becomes stronger. Originality/value – The present results are new and original for the heat transfer and fluid flow in a porous tilted triangle enclosure filled by Cu-water nanofluid. The results would benefit scientists and engineers to become familiar with the flow behaviour of such nanofluids, and the way to predict the properties of this flow for possibility of using nanofluids in advanced nuclear systems, in industrial sectors including transportation, power generation, chemical sectors, ventilation, air-conditioning, etc.

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Numerical Investigation of Laminar Natural Convection in Inclined Square Enclosure with the Influence of Discrete Heat Source

Journal of Applied Mathematics ◽

10.1155/2015/985218 ◽

2015 ◽

Vol 2015 ◽

pp. 1-9 ◽

Cited By ~ 1

Author(s):

Chithra Devaraj ◽

Eswaramurthi Muthuswamy ◽

Sundararaj Kandasamy

Keyword(s):

Heat Transfer ◽

Nusselt Number ◽

Natural Convection ◽

Heat Source ◽

Average Nusselt Number ◽

Convection Heat Transfer ◽

Correlation Coefficients ◽

Computational Procedure ◽

Square Enclosure ◽

Rayleigh Numbers

Natural convection heat transfer in a two-dimensional square enclosure at various angles of inclination is investigated numerically using a finite volume based computational procedure. The heat transfer is from a constant temperature heat source of finite length centred at one of the walls to the cold wall on the opposite side while the remaining walls are insulated. The effect of area ratio of the heat sourceAfrom 0.2 to 1.0, Rayleigh number Ra from 103to 107, and angle of inclination of the enclosureθvarying from 0° to 360° on the flow field and heat transfer characteristics are investigated. Streamline and isothermal line patterns are found to be similar at low Rayleigh numbers whereas at high Rayleigh numbers the differences are significant due to the influence of the parameters considered. Average Nusselt number decreases drastically as the position of the heat source is moved above the horizontal centre line of the enclosure. Correlation of the average Nusselt number which depends on the parameters of interest is obtained in the general formCRamAn. The correlation coefficients are determined by multiple regression analysis for the entire range of Rayleigh numbers analysed and the values found by correlation equations are in good agreement with the numerical results.

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Natural convection of Newtonian fluids between two concentric cylinders of a special cross-sectional form

Thermal Science ◽

10.2298/tsci200201190l ◽

2020 ◽

pp. 190-190

Author(s):

Houssem Laidoudi ◽

Mustapha Helmaoui ◽

Mohamed Bouzit ◽

Abdellah Ghenaim

Keyword(s):

Heat Transfer ◽

Nusselt Number ◽

Natural Convection ◽

Rayleigh Number ◽

Prandtl Number ◽

Inclination Angle ◽

Average Nusselt Number ◽

Outer Cylinder ◽

Cross Sectional ◽

The Mean

In this paper, we performed a numerical simulation of natural convection of Newtonian fluids between two cylinders of different cross-sectional form. The inner cylinder is supposed to be hot and the outer cylinder is assumed to be cold. The diameter of inner cylinder to the diameter of outer cylinder defines the radii ratio (RR= 2.5). The governing equations describing the physical behavior of fluid flow and heat transfer are solved using finite volume method. The effects of Prandtl number (Pr = 0.71 to 100), Rayleigh number (Ra = 103 to 105) and inclination angle of inner cylinder (? = 0? to 80?) on streamlines, isotherms and dimensionless velocity are presented and discussed. Also, the mean average Nusselt number of inner cylinder is plotted versus the governing parameters. All present simulations are considered in two-dimensions for steady laminar flow regime. The obtained results showed that the flow between cylinders is more stable for the inclination angle ? = 0?. Increase in Rayleigh number increases the heat transfer rate for all values of inclination angle. Furthermore, the effect of Prandtl number on the mean average Nusselt number becomes negligible when Pr is over the value 7.01. For example at Pr = 0.71 and Ra =105, increase in inclination from 0? to 40?decreases the average Nusselt number by 5.4%. A new correlation is also provided to describe the average Nusselt number as function of Pr and Ra at ? = 0?.

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Numerical Analysis of Natural Convection Heat Transfer From a Vertical Hollow Cylinder Suspended in Air

Journal of Heat Transfer ◽

10.1115/1.4038478 ◽

2018 ◽

Vol 140 (5) ◽

Cited By ~ 9

Author(s):

Swastik Acharya ◽

Sumit Agrawal ◽

Sukanta K. Dash

Keyword(s):

Heat Transfer ◽

Nusselt Number ◽

Natural Convection ◽

Rayleigh Number ◽

Hollow Cylinder ◽

Outer Surface ◽

Average Nusselt Number ◽

Convection Heat Transfer ◽

Natural Convection Heat Transfer ◽

Convection Heat

Natural convection heat transfer from a vertical hollow cylinder suspended in air has been analyzed numerically by varying the Rayleigh number (Ra) in the laminar (104 ≤ Ra ≤ 108) regime. The simulations have been carried out by changing the ratio of length to pipe diameter (L/D) in the range of 0.05 ≤ L/D≤20. Full conservation equations have been solved numerically for a vertical hollow cylinder suspended in air using algebraic multigrid solver of fluent 13.0. The flow and the temperature field around the vertical hollow cylinder have been observed through velocity vectors and temperature contours for small and large L/D. It has been found that the average Nusselt number (Nu) for vertical hollow cylinder suspended in air increases with the increase in Rayleigh number (Ra) and the Nu for both the inner and the outer surface also increases with Ra. However, with the increase in L/D, average Nu for the outer surface increases almost linearly, whereas the average Nu for the inner surface decreases and attains asymptotic value at higher L/D for low Ra. In this study, the effect of parameters like L/D and Ra on Nu is analyzed, and a correlation for average Nusselt number has been developed for the laminar regime. These correlations are accurate to the level of ±6%.

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