scholarly journals Effect of thermal buoyancy on flow pattern from a pair of side-by-side confined triangular cylinders

2020 ◽  
Vol 55 (1) ◽  
pp. 9-14
Author(s):  
H Laidoudi ◽  
M Bouzit
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Drag Coefficient ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Richardson Number ◽  
Average Nusselt Number ◽  
Convection Heat Transfer ◽  
Thermal Buoyancy ◽  
Energy Equations

The effects of ax ial and radial thermal buoyancy on fluid flow and mixed convection heat transfer from a pair of identical triangular cylinders in side-by-side arrangement confined within a straight channel. The numerical simulations are carried out by solving continuity, momentum and energy equations using the commercial code ANSYS-CFX. The obtained results are presented and discussed within the range of following conditions: Richardson number Ri = 0 to 2, Reynolds Re = 20, and Prandtl number Pr = 1 at fixed value of blockage ratio β = 0.2. The main results are depicted in terms of streamline and isotherm contours to analyze the fluidic and energetic behaviors. The total drag coefficient and average Nusselt number are also computed. Moreover, a simple correlation indicating the variations of drag coefficient and average Nusselt number versus Richardson number are also provided. It was found that for axial effect of thermal buoyancy, increase in buoyancy strength enhances the heat transfer rate for both cylinders. In other hand, for radial effect, increase in buoyancy strength increases the heat transfer rate of down cylinder and it is reduced for the upper cylinder. Bangladesh J. Sci. Ind. Res.55(1), 9-14, 2020

scholarly journals Mixed convection heat transfer from a heated circular cylinder

2019 ◽  
Vol 54 (1) ◽  
pp. 83-88
Author(s):  
H Laidoudi ◽  
M Bouzit
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Drag Coefficient ◽  
Average Nusselt Number ◽  
Convection Heat Transfer ◽  
Circular Cylinders ◽  
Governing Equations ◽  
Thermal Buoyancy ◽  
Flow And Heat Transfer ◽  
Mixed Convection Heat Transfer

This paper performs the effects of thermal buoyancy and the triangular arrangement of circular cylinders on fluid flow and heat transfer within a horizontal channel, the governing equations involving continuity; momentum and energy are solved in two-dimensional, laminar and steady flow regime. The average Nusselt number and drag coefficient are computed for the range of these conditions: Ri = 0 to 2 at fixed value of Pr = 1, Reynolds number Re = 30 and geometrical configurations (blockage ratio of β = 0.1). In order to observe the flow structure and temperature field under the gradual effect of thermal buoyancy, the streamlines and isotherm contours are illustrated. It is found that, a gradual increase in the value of buoyancy strength creates an asymmetrical flow around the cylinders. Interesting variations of drag coefficient and average Nusselt number are plotted with respect to Richardson number for each cylinder. Bangladesh J. Sci. Ind. Res.54(1), 83-88, 2019

The Flow and Mixed Convection around Tandem Circular Cylinders at Low Reynolds Number

2017 ◽  
Vol 378 ◽  
pp. 59-67
Author(s):  
Houssem Laidoudi ◽  
Blissag Bilal ◽  
Mohamed Bouzit
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Mixed Convection ◽  
Drag Coefficient ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Richardson Number ◽  
Circular Cylinders ◽  
Thermal Buoyancy ◽  
Flow And Heat Transfer

A numerical investigation is carried out to understand the effects of thermal buoyancy and Reynolds number on flow characteristics and mixed convection heat transfer over three isothermal circular cylinders situated in a tandem arrangement within a horizontal channel. The distance between cylinders is fixed at the value of 2.5 widths of the cylinder. The obtained results are presented and discussed for the range of conditions as: Re = 5 to 40, Ri = 0 to 2 at fixed Pr number of 1 and blockage ratio β = 0.25. The main results are depicted in terms of streamlines and isotherm contours to analyze the effect of thermal buoyancy on fluid flow and heat transfer rate. Moreover, the overall drag coefficient and Nusselt number are computed to elucidate the role of Reynolds number and Richardson number on the flow and heat transfer. It is found that increase in the Richardson number increases the drag coefficient of the upstream cylinder whereas it decreases the heat transfer rate of this cylinder. The superimposed of thermal buoyancy created a new sort of recirculation zones between the tandem cylinders.

scholarly journals 3D Simulation of Incompressible Poiseuille Flow through 180° Curved Duct of Square Cross-section under Effect of Thermal Buoyancy

2019 ◽  
Vol 63 (4) ◽  
pp. 257-269 ◽  
Author(s):  
Mourad Mokeddem ◽  
Houssem Laidoudi ◽  
Oluwole Daniel Makinde ◽  
Mohamed Bouzit
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Heat Transfer Rate ◽  
Cross Section ◽  
Transfer Rate ◽  
Richardson Number ◽  
Dean Number ◽  
Thermal Buoyancy ◽  
Dimensionless Velocity ◽  
Curved Duct

In this paper, three-dimensional numerical simulations are carried out to investigate and analyze the gradual effects of thermal buoyancy strength on laminar flow of an incompressible viscous fluid and heat transfer rate inside a 180° curved channel of square cross-section. The governing equations of continuity, momentum and energy balance are obtained and solved numerically using finite volume method. The effect of Dean number, De, and Richardson number, Ri, on dimensionless velocity profiles and Nusselt number are examined for the conditions: De = 125 to 150, Ri = 0 to 2 at Pr = 1. The mean results are illustrated in terms of streamline and isotherm contours to interpret the flow behaviors and its effect on heat transfer rate. Dimensionless velocity profiles and the local Nusselt number at the angle 0° and 90° are presented and discussed. Also, the average Nusselt number on surfaces of curved duct is computed. The obtained results showed that by adding thermal buoyancy to computed domain, some early Dean vortices are observed at the angle 0° and new sort are observed at 90°. Furthermore, increase in Dean number increases the heat transfer rate. In other hand, increase in Richardson number decreases the average Nusselt number of 180° curved duct.

Forced convection heat transfer study of a blunt-headed cylinder in non-Newtonian power-law fluids

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Jaspinder Kaur ◽  
Roderick Melnik ◽  
Anurag Kumar Tiwari
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Drag Coefficient ◽  
Power Law ◽  
Average Nusselt Number ◽  
Convection Heat Transfer ◽  
Convection Heat ◽  
Total Drag ◽  
Shear Thinning Fluids ◽  
Power Law Fluids

Abstract In this present work, forced convection heat transfer from a heated blunt-headed cylinder in power-law fluids has been investigated numerically over the range of parameters, namely, Reynolds number (Re): 1–40, Prandtl number (Pr): 10–100 and power-law index (n): 0.3–1.8. The results are expressed in terms of local parameters, like streamline, isotherm, pressure coefficient, and local Nusselt number and global parameters, like wake length, drag coefficient, and average Nusselt number. The length of the recirculation zone on the rear side of the cylinder increases with the increasing value of Re and n. The effect of the total drag coefficient acting on the cylinder is seen to be higher at the low value of Re and its effect significant in shear-thinning fluids (n < 1). On the heat transfer aspect, the rate of heat transfer in fluids is increased by increasing the value of Re and Pr. The effect of heat transfer is enhanced in shear-thinning fluids up to ∼ 40% and it impedes it’s to ∼20% shear-thickening fluids. In the end, the numerical results of the total drag coefficient and average Nusselt number (in terms of J H −factor) have been correlated by simple expression to estimate the intermediate value for the new application.

Heat Transfer Investigation of a Tube Partially Wrapped by Metal Porous Layer as a Potential Novel Tube for Air Cooled Heat Exchangers

2018 ◽  
Vol 141 (1) ◽  
Author(s):  
M. Mohammadpour-Ghadikolaie ◽  
M. Saffar-Avval ◽  
Z. Mansoori ◽  
N. Alvandifar ◽  
N. Rahmati
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Heat Transfer Rate ◽  
Porous Layer ◽  
Transfer Rate ◽  
Metal Foam ◽  
Convection Heat Transfer ◽  
Darcy Number ◽  
High Heat Transfer

Laminar forced convection heat transfer from a constant temperature tube wrapped fully or partially by a metal porous layer and subjected to a uniform air cross-flow is studied numerically. The main aim of this study is to consider the thermal performance of some innovative arrangements in which only certain parts of the tube are covered by metal foam. The combination of Navier–Stokes and Darcy–Brinkman–Forchheimer equations is applied to evaluate the flow field. Governing equations are solved using the finite volume SIMPLEC algorithm and the effects of key parameters such as Reynolds number, metal foam thermophysical properties, and porous layer thickness on the Nusselt number are investigated. The results show that using a tube which is fully wrapped by an external porous layer with high thermal conductivity, high Darcy number, and low drag coefficient, can provide a high heat transfer rate in the high Reynolds number laminar flow, increasing the Nusselt number almost as high as 16 times compared to a bare tube. The most important result of thisstudy is that by using some novel arrangements in which the tube is partially covered by the foam layer, the heat transfer rate can be increased at least 20% in comparison to the fully wrapped tube, while the weight and material usage can be considerably reduced.

Numerical simulation of water/alumina nanofluid mixed convection in square lid-driven cavity

2019 ◽  
Vol 30 (5) ◽  
pp. 2781-2807
Author(s):  
Davood Toghraie ◽  
Ehsan Shirani
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Mixed Convection ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Richardson Number ◽  
Hartmann Number ◽  
Two Phase ◽  
Content Type ◽  
Driven Cavity

Purpose The purpose of this paper is to investigate the mixed convection of a two-phase water–aluminum oxide nanofluid in a cavity under a uniform magnetic field. Design/methodology/approach The upper wall of the cavity is cold and the lower wall is warm. The effects of different values of Richardson number, Hartmann number, cavitation length and solid nanoparticles concentration on the flow and temperature field and heat transfer rate were evaluated. In this paper, the heat flux was assumed to be constant of 10 (W/m2) and the Reynolds number was assumed to be constant of 300 and the Hartmann number and the volume fraction of solid nanoparticles varied from 0 to 60 and 0 to 0.06, respectively. The Richardson number was considered to be 0.1, 1 and 5. Aspect ratios were 1, 1.5 and 2. Findings Comparison of the results of this paper with the results of the numerical and experimental studies of other researchers showed a good correlation. The results were presented in the form of velocity and temperature profiles, stream and isotherm lines and Nusselt numbers. The results showed that by increasing the Hartmann number, the heat transfer rate decreases. An increase from 0 to 20 in Hartmann number results in a 20 per cent decrease in Nusselt numbers, and by increasing the Hartmann number from 20 to 40, a 16 per cent decrease is observed in Nusselt number. Accordingly, it is inferred that by increasing the Hartmann number, the reduction in the Nusselt number is decreased. As the Richardson number increased, the heat transfer rate and, consequently, the Nusselt number increased. Therefore, an increase in the Richardson number results in an increase of the Nusselt number, that is, an increase in Richardson number from 0.1 to 1 and from 1 to 5 results in 37 and 47 per cent increase in Nusselt number, respectively. Originality/value Even though there have been numerous investigations conducted on convection in cavities under various configurations and boundary conditions, relatively few studies are conducted for the case of nanofluid mixed convection in square lid-driven cavity under the effect of magnetic field using two-phase model.

Numerical study of the fin effect on mixed convection heat transfer in a lid-driven cavity

2010 ◽  
Vol 225 (2) ◽  
pp. 397-406 ◽  
Author(s):  
A A R Darzi ◽  
M Farhadi ◽  
K Sedighi
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Richardson Number ◽  
Numerical Study ◽  
Convection Heat Transfer ◽  
Thermal Conductivity Ratio ◽  
Driven Cavity ◽  
Ratio Change ◽  
Vertical Walls ◽  
Energy Equations

In this study, the mixed convective heat transfer in a lid-driven cavity was investigated numerically. The finite volume discritization method was used to solve the momentum and energy equations by using the classic Boussinesq incompressible approximation. The cavity vertical walls are insulated whereas the bottom (hot wall) and top (cold wall) surface are maintained at a uniform temperature and fins are located on bottom wall. The effect of fin numbers over the flow field and heat transfer was investigated at various Richardson numbers. Study was carried out for Richardson numbers ranging from 0.01 to 10, fin numbers between 1 and 7, fin height ratio change from 0.05 to 0.3, and thermal conductivity ratio (fin to fluid) from 10 to 104, respectively. The results are presented in the form of streamlines, temperature contours, and Nusselt number distributions. The results show that the Nusselt number increases when the number of fin and fin height decrease. In addition, in all cases an increasing Richardson number caused increasing the relative Nusselt number ( Nu / Nu0). The heat transfer enhancement was observed at low fin numbers (1 and 3) and high Richardson number in comparison with the cavity without fins.

scholarly journals Natural Convection from Four Circular Cylinders in Across Arrangement within Horizontal Annular Space

2020 ◽  
Vol 14 (2) ◽  
pp. 98-102
Author(s):  
Houssem Laidoudi
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Natural Convection ◽  
Prandtl Number ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Initial Conditions ◽  
Fluid Motion ◽  
Circular Cylinders ◽  
Thermal Buoyancy

AbstractNumerical investigation is accomplished to study the roles of governing parameters of natural convection on the fluid motion and heat transfer rate of four heated circular cylinders placed inside a circular enclosure of cold surface. The cylinders are positioned in across arrangement. The representative results are obtained within the ranges of initial conditions as: Prandtl number (Pr = 7.1 to 1000) and Rayleigh number (Ra = 103 to 105). The average Nusselt number of each inner cylinder is computed. The effects of thermal buoyancy strength on the fluid motion and temperature are also illustrated. It was found that the heat transfer rate of cylinders depends significantly on the position inside the enclosure. Moreover, the role of Prandtl number on flow and thermal patterns is negligible. The values of Nusselt number are also given, which can be useful for some engineering applications.

Simulation of Non Newtonian Power-Law Fluid Flows and Mixed Convection Heat Transfer inside of Curved Duct

2017 ◽  
Vol 378 ◽  
pp. 113-124 ◽  
Author(s):  
Bouzit Fayçal ◽  
Houssem Laidoudi ◽  
Mohamed Bouzit
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Rate ◽  
Power Law ◽  
Transfer Rate ◽  
Richardson Number ◽  
Flow Behavior ◽  
Thermal Buoyancy ◽  
Flow And Heat Transfer ◽  
Curved Duct ◽  
Power Law Fluids

A two-dimensional numerical simulation is carried out to understand the combined effects of thermal buoyancy strength and rheological flow behavior of non Newtonian power-law fluids on laminar flow and heat transfer rate through a 180° curved duct. The governing equations including the full Navier-Stokes, the continuity and the energy are solved using the commercial code ANSYS-CFX. The numerical results are presented and discussed for the range of conditions as: Re = 40 to 1000, Ri = 0 to 1 and n = 0.4 to 1.2 for fixed value of Prandt number of Pr = 1. In order to analyze the obtained results, the representative streamlines and isotherm patterns are presented. The average Nusselt number of the inner and outer walls of duct is computed to determine the role of Reynolds number, Richardson number and power-law index on flow and heat transfer. It is found that increase in Richardson number creates alternative vortices on duct walls. Moreover, the alternative vortices enhance the heat transfer rate for shear thinning, Newtonian and shear thickening fluids.

Mixed Convection Heat Transfer around a Tandem Circular Cylinders in Incompressible Downward Flow

2018 ◽  
Vol 16 ◽  
pp. 12-20
Author(s):  
Houssem Laidoudi ◽  
Oluwole Daniel Makinde
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Convection Heat Transfer ◽  
Vertical Channel ◽  
Circular Cylinders ◽  
Thermal Buoyancy ◽  
Flow And Heat Transfer ◽  
Mixed Convective Flow

In this paper, we numerically examine the mixed convective flow around a confined tandem heated circular cylinders embedded in a vertical channel in order to determine exactly the effects of opposing thermal buoyancy and distance between cylinders (S) on the behavior of fluid flow and heat transfer rate. The dimensionless governing equations involving momentum, continuity and energy are obtained and solved in a steady laminar flow regime for the conditions:Re= 5 to 40 andS= 0 to 5d, at fixed values of Prandtl numberPr= 1, Richardson numberRi= 1 and blockage ratioβ= 1/5. The fluid flow and temperature field are illustrated in terms of streamline and isotherm contours. The average Nusselt number is also computed to quantify the effect of fluid flow and heat transfer characteristics on amount of heat transfer rate.

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