Effect of Driven Sidewalls on Mixed Convection in an Open Trapezoidal Cavity With a Channel

2020 ◽  
Vol 142 (8) ◽  
Author(s):  
Muneer A. Ismael ◽  
Ahmed Kadhim Hussein ◽  
Fateh Mebarek-Oudina ◽  
Lioua Kolsi
Keyword(s):  
Reynolds Number ◽  
Nusselt Number ◽  
Mixed Convection ◽  
Richardson Number ◽  
Average Nusselt Number ◽  
Airflow Velocity ◽  
Driven Cavity ◽  
Thermal Fields ◽  
Number Ratio ◽  
The Right

Abstract The mixed convection in an open trapezoidal lid-driven cavity connected with a channel is investigated in the present paper. Four different cases were considered depending on the movement of the cavity sidewalls. For case I, the left sidewall moves downward; for case II, the left sidewall moves downward and the right one moves upward; while for case III, only the right sidewall moves upward. A comparative case (case 0) is accounted when both sidewalls are assumed stationary. The base of the cavity is subjected to a localized heat source of constant temperature Th. The effects of Richardson number Ri and Reynolds number ratio Rer on the flow and thermal fields have been investigated. The results indicated that for cases I and II, the average Nusselt number increases with the increase of the Richardson number and Reynolds number ratio. Moreover, it was found that the maximum average Nusselt number occurs with case I. When the lid-driven speed is three times that of the inlet airflow velocity, the augmentations of the average Nusselt number compared with stationary walls are 163%, 158%, and 96% for cases I, II, and III, respectively.

Analysis of mixed convection past a heated sphere

2018 ◽  
Vol 233 (3) ◽  
pp. 601-616 ◽  
Author(s):  
Dipjyoti Nath ◽  
Sukumar Pati ◽  
B Hema Sundar Raju
Keyword(s):  
Reynolds Number ◽  
Nusselt Number ◽  
Prandtl Number ◽  
Mixed Convection ◽  
Drag Coefficient ◽  
Richardson Number ◽  
Average Nusselt Number ◽  
Thermal Characteristics ◽  
Sphere Surface ◽  
Critical Richardson Number

The hydrodynamic and thermal characteristics for laminar axisymmetric mixed convection from a heated sphere are analyzed numerically in this work. The governing transport equations of conservation of mass, momentum, and energy have been solved using a higher order compact scheme. The results are presented in terms of the distribution of the streamlines, isotherms, and vorticity contours, and local Nusselt number along the sphere surface together with drag coefficient and average Nusselt number. We identify critical Richardson number above which separation of flow is suppressed. It is revealed that the drag coefficient decreases with an increase in the Reynolds number (Re) and the decrease is more profound for lower range of Re. It is further revealed that the drag coefficient increases monotonically with an increase in the Richardson number, while the same decreases with the increase in the Prandtl number. The average Nusselt number increases monotonically with the increase in Reynolds number, Prandtl number, and Richardson number.

Simulation of Mixed Convection Air Cooling of Protruding Heat Sources Mounted on One Side of a Vertical Channel

2011 ◽  
Author(s):  
Rajat Dhingra ◽  
P. S. Ghoshdastidar
Keyword(s):  
Reynolds Number ◽  
Nusselt Number ◽  
Regression Analysis ◽  
Mixed Convection ◽  
Richardson Number ◽  
Average Nusselt Number ◽  
Vertical Channel ◽  
Separation Distance ◽  
Air Cooling ◽  
Heat Sources

A numerical study of steady, laminar, two-dimensional mixed convection air cooling of identical as well as non-identical rectangular protruding heat sources located on one side of a vertical channel is presented in this paper. The stream function-vorticity-temperature approach with the finite-difference-based methodology implementing higher order upwind scheme has been applied. Three cases have been considered, namely (i) when the number of identical chips is two; (ii) when the number varies from 3 to 10; and finally, (iii) when five chips of different heights but of same width are placed in various orders. For the case of two chips the effects of Re, Gr/Re2 (that is, Richardson number), dimensionless separation distance between the chips (d/H), dimensionless chip height (h/H) and width (w/H) on the average Nusselt number of each chip have been investigated. A correlation based on regression analysis is also presented for each parameter. With increase in Reynolds number the average Nusselt number of both chips increases. Similar trend is seen when the separation distance between two chips is raised. It is also observed that as the number of chips escalates from 2 to 10, the average Nusselt number of downstream chips becomes smaller than that of the upstream chips, the rate of drop being much sharper near the channel inlet. A regression-analysis based composite correlation each for average Nusselt number of Chip 1 (lower chip) and Chip 2 (upper chip) as a function of Reynolds number, Richardson number, separation distance between the chips, chip height and width has been obtained for the 2-chip case. The model also predicts maximum chip temperature in an array of ten chips. Finally, for five non-identical chips having same width but different heights the simulation reveals that the chips placed in increasing order of their heights in the direction of air flow are cooled better as compared to any other pattern of placement of the chips.

A Numerical Investigation of Laminar Mixed Convection Flow and Heat Transfer in a Lid Driven Cavity with Two Cylinders

2015 ◽  
Vol 789-790 ◽  
pp. 282-286 ◽  
Author(s):  
Khalil Khanafer ◽  
M. El Haj Assad
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Mixed Convection ◽  
Richardson Number ◽  
Average Nusselt Number ◽  
Convection Flow ◽  
Mixed Convection Flow ◽  
Driven Cavity ◽  
Flow And Heat Transfer ◽  
The Impact

Mixed convection flow and heat transfer characteristics in a lid-driven cavity with two isothermally heated circular cylinders inside are studied numerically using a finite element formulation based on the Galerkin method of weighted residuals. The top lid of the cavity is moving rightwards with a constant speed. The two cylinders are maintained at an isothermal hot temperature, while the walls of the cavity are maintained at a cold temperature. Comparisons of streamlines, isotherms and average Nusselt number are presented to show the impact of the Richardson number, non-dimensional radius of the cylinder, and the location of the cylinders on the transport phenomena within the cavity. The results of this investigation show that the presence of the cylinders results in an increase in the average Nusselt number compared with a case with no cylinder. The average Nusselt number increases with an increase in the Richardson number for all non-dimensional radius of the cylinder studied in this work. It is seen that changing the boundary condition on one of the cylinders from isothermal to adiabatic has minimal effect on the average Nusselt number around the walls of the cavity.

scholarly journals Magnetohydrodynamics Mixed Convection Around a Heat Conducting Horizontal Circular Cylinder in a Rectangular Lid-driven Cavity with Joule Heating

2009 ◽  
Vol 1 (3) ◽  
pp. 461-472 ◽  
Author(s):  
M. M. Rahman ◽  
M. A. Alim ◽  
M. K. Chowdhury
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Mixed Convection ◽  
Richardson Number ◽  
Average Nusselt Number ◽  
Hartmann Number ◽  
Heat Conducting ◽  
Fluid Temperature ◽  
Driven Cavity ◽  
Horizontal Circular Cylinder

In the present paper, a study of magnetohydrodynamic (MHD) mixed convection around a heat conducting horizontal circular cylinder placed at the center of a rectangular cavity along with joule heating has been carried out. Steady state heat transfer by laminar mixed convection has been studied numerically by solving the equations of mass, momentum and energy to determine the fluid flow and heat transfer characteristics in the cavity as a function of Richardson number, Hartmann number and the cavity aspect ratio. The results are presented in the form of average Nusselt number at the heated surface; average fluid temperature in the cavity and temperature at the cylinder center for the range of Richardson number, Hartmann number and aspect ratio. The streamlines and isotherms are also presented. It is found that the streamlines, isotherms, average Nusselt number, average fluid temperature and dimensionless temperature at the cylinder center strongly depend on the Richardson number, Hartmann number and the cavity aspect ratio.Keywords: Mixed convection; Finite element method; Cylinder diameter; Lid-driven cavity; Hartmann number. © 2009 JSR Publications. ISSN: 2070-0237 (Print); 2070-0245 (Online). All rights reserved. DOI: 10.3329/jsr.v1i3.2597               J. Sci. Res. 1 (3), 461-472 (2009) 

Numerical Analysis of Laminar Mixed Convection in a Lid Driven Square Cavity With an Isothermally Heated Square Internal Blockage

2012 ◽  
Author(s):  
Akand W. Islam ◽  
Muhammad A. R. Sharif ◽  
Eric S. Carlson
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Mixed Convection ◽  
Richardson Number ◽  
Average Nusselt Number ◽  
Blockage Ratio ◽  
Square Cavity ◽  
Ansys Fluent ◽  
Laminar Mixed Convection

Laminar mixed convection characteristics in a square cavity with an isothermally heated square blockage inside have been investigated numerically using the finite volume method of the ANSYS FLUENT commercial CFD code. Various different blockage sizes and concentric and eccentric placement of the blockage inside the cavity have been considered. The blockage is maintained at a hot temperature, Th, and four surfaces of the cavity (including the lid) are maintained at a cold temperature, Tc, under all circumstances. The physical problem is represented mathematically by sets of governing conservation equations of mass, momentum, and energy. The geometrical and flow parameters for the problem are the blockage ratio (B), the blockage placement eccentricities (εx and εy), the Reynolds number (Re), the Grashof number (Gr), and the Richardson number (Ri). The flow and heat transfer behavior in the cavity for a range of Richardson number (0.01–100) at a fixed Reynolds number (100) and Prandtl number (0.71) is examined comprehensively. The variations of the average and local Nusselt number at the blockage surface at various Richardson numbers for different blockage sizes and placement eccentricities are presented. From the analysis of the mixed convection process, it is found that for any size of the blockage placed anywhere in the cavity, the average Nusselt number does not change significantly with increasing Richardson number until it approaches the value of the order of 1 beyond which the average Nusselt number increases rapidly with the Richardson number. For the central placement of the blockage at any fixed Richardson number, the average Nusselt number decreases with increasing blockage ratio and reaches a minimum at around a blockage ratio of slightly larger than 1/2. For further increase of the blockage ratio, the average Nusselt number increases again and becomes independent of the Richardson number. The most preferable heat transfer (based on the average Nusselt number) is obtained when the blockage is placed around the top left and the bottom right corners of the cavity.

scholarly journals Mixed convection of functionalized DWCNT-water nanofluid in baffled lid-driven cavities

2018 ◽  
Vol 22 (6 Part A) ◽  
pp. 2503-2514 ◽  
Author(s):  
Esfe Hemmat ◽  
Arani Abbasian ◽  
Wei-Mon Yan ◽  
Alireza Aghaie ◽  
Masoud Afrand ◽  
...  
Keyword(s):  
Nusselt Number ◽  
Mixed Convection ◽  
Richardson Number ◽  
Average Nusselt Number ◽  
Volume Fraction ◽  
Minimum Length ◽  
Convection Flow ◽  
Flow And Heat Transfer ◽  
Inclination Angles ◽  
Nanoparticles Volume Fraction

The present study aims to evaluate the mixed convection flow and heat transfer of functionalized DWCNT/water nanofluids with variable properties in a cavity having hot baffles. The investigation is performed at different nanoparticles volume fraction including 0, 0.0002, 0.001, 0.002, and 0.004, Richardson numbers ranging from 0.01 to 100, inclination angles ranging from 0 to 60? and at constant Grashof number of 104. The results presented as streamlines and isotherms plot and Nusselt number diagrams. According to the finding with increasing nanoparticles volume fraction and distance between the left hot baffles of nanoparticles average Nusselt number enhances for all considered Richardson numbers and cavity inclination angles. Also with increasing Richardson number, the rate of changes of average Nusselt number increase with increasing distance between the left hot baffles. For example, at Richardson number of 0.01, by increasing L1 from 0.4 to 0.6, the average Nusselt number increases 7%; while for similar situation at Richardson number of 0.1, 1.0, and 10, the average Nusselt number increases, respectively, 17%, 24%, and 26%. At all Richardson numbers, the maximum value of average Nusselt number is achieved for a minimum length of left baffles. <br><br><font color="red"><b> This article has been corrected. Link to the correction <u><a href="http://dx.doi.org/10.2298/TSCI190203032E">10.2298/TSCI190203032E</a><u></b></font>

scholarly journals Mixed Convection and Entropy Generation of an Ag-Water Nanofluid in an Inclined L-Shaped Channel

Energies ◽  
2019 ◽  
Vol 12 (6) ◽  
pp. 1150 ◽  
Author(s):  
Taher Armaghani ◽  
Muneer Ismael ◽  
Ali Chamkha ◽  
Ioan Pop
Keyword(s):  
Nusselt Number ◽  
Mixed Convection ◽  
Entropy Generation ◽  
Richardson Number ◽  
Volume Fraction ◽  
Governing Equations ◽  
Nanoparticles Volume Fraction ◽  
The Mean ◽  
The Right ◽  
Volume Method

This paper investigates the mixed convection and entropy generation of an Ag-water nanofluid in an L-shaped channel fixed at an inclination angle of 30° to the horizontal axis. An isothermal heat source was positioned in the middle of the right inclined wall of the channel while the other walls were kept adiabatic. The finite volume method was used for solving the problem’s governing equations. The numerical results were obtained for a range of pertinent parameters: Reynolds number, Richardson number, aspect ratio, and the nanoparticles volume fraction. These results were Re = 50–200; Ri = 0.1, 1, 10; AR = 0.5–0.8; and φ = 0.0–0.06, respectively. The results showed that both the Reynolds and the Richardson numbers enhanced the mean Nusselt number and minimized the rate of entropy generation. It was also found that when AR. increased, the mean Nusselt number was enhanced, and the rate of entropy generation decreased. The nanoparticles volume fraction was predicted to contribute to increasing both the mean Nusselt number and the rate of entropy generation.

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.

Laminar Mixed Convection of Non-Newtonian Nanofluids Flowing Vertically Upward Across a Confined Circular Cylinder

2018 ◽  
Vol 10 (4) ◽  
Author(s):  
Abhipsit Kumar Singh ◽  
Nanda Kishore
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Circular Cylinder ◽  
Mixed Convection ◽  
Richardson Number ◽  
Average Nusselt Number ◽  
Volume Fraction ◽  
Numerical Results ◽  
Total Drag ◽  
Drag Coefficients

Numerical results on laminar mixed convective heat transfer phenomenon between a confined circular cylinder and shear-thinning type nanofluids are presented. The cylinder is placed horizontally in a confined channel through which nanofluids flow vertically upward. The effect of buoyancy is same as the direction of the flow. Because of existence of mixed convection, governing continuity, momentum, and energy equations are simultaneously solved within the limitations of Boussinesq approximation. The ranges of parameters considered are: volume fraction of nanoparticles, ϕ = 0.005–0.045; Reynolds number, Re = 1–40; Richardson number, Ri = 0–40; and confinement ratio of circular cylinder, λ = 0.0625–0.5. Finally, the effects of these parameters on the streamlines, isotherm contours, individual and total drag coefficients, and local and average Nusselt numbers are thoroughly delineated. The individual and total drag coefficients decrease with the increasing both ϕ and Re; and/or with the decreasing both Ri and λ. The rate of heat transfer increases with the increasing Re, ϕ, Ri, and λ; however, at Re = 30–40, when ϕ > 0.005 and Ri < 2, the average Nusselt number decreases with the increasing Richardson number. Finally, correlations for the total drag coefficient and average Nusselt number are proposed as functions of pertinent dimensionless parameters on the basis of present numerical results.

Numerical Investigation of a Three-Dimensional Laminar Mixed Convection Flows in Lid-Driven Cavity for Very Small Richardson Numbers

2015 ◽  
Author(s):  
M. M. Abo Elazm ◽  
A. I. Shahata ◽  
A. F. Elsafty ◽  
M. A. Teamah
Keyword(s):  
Nusselt Number ◽  
Mixed Convection ◽  
Richardson Number ◽  
Three Dimensional ◽  
Lewis Number ◽  
Maximum Error ◽  
Driven Cavity ◽  
Laminar Mixed Convection ◽  
Nusselt Number Distribution ◽  
Volume Method

Laminar mixed convection in a three-dimensional lid driven cavity is numerically investigated. The top lid of the cavity is moving rightwards with a constant speed at a cold temperature. The bottom wall is maintained at an isothermal hot temperature, while the other vertical walls of the cavity are assumed to be insulated. In this study the mass diffusion was not taken into account and the fluid used was air. The flow and heat transfer behavior is studied for various Richardson number ranging from 5 × 10−5 to 3 × 10−4 at a fixed Prandtl number of 0.71 through analyzing the local Nusselt number distribution at different sections inside the cavity. Lewis number Le is assumed to be unity and the buoyancy ratio parameter N is equal to zero. Computations were done using an in-house code based on a finite volume method. The results showed a good agreement with previous two dimensional studies, while the three dimensional study gives different results at different sections inside the cavity. It is observed that, the average Nusselt number “Av Nu” on top and bottom surfaces decreases for all sections inside the cavity with increasing Richardson number. A correlation was formulated for each section on both walls for “Av Nu” as a function of “Ri” with a maximum error of 7.3%.

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