scholarly journals Optimum Cooling Based on the Exit Openings Position for Turbulent Mixed Convection in Ventilated Cavities

2020 ◽  
Vol 64 (4) ◽  
pp. 307-316
Author(s):  
Mohamed Chaour ◽  
Saadoun Boudebous ◽  
Abdelkader Filali
Keyword(s):  
Mixed Convection ◽  
Turbulence Modeling ◽  
Vertical Wall ◽  
Elimination Rate ◽  
Simple Algorithm ◽  
Ansys Fluent ◽  
Total Temperature ◽  
The Right ◽  
Volume Method ◽  
Heat Elimination

In this paper, turbulent mixed convection in a ventilated square cavity exposed to a cooling of the blocks is studied numerically. The cavity walls were kept adiabatic except the right vertical wall which was equipped with three blocks dissipating the heat at a constant temperature. The commercial Ansys Fluent code is used and governing equations were established and discretized by the finite volume method. The standard k-ε model is considered for the turbulence modeling and SIMPLE algorithm is used for the pressure – velocity coupling. The objective of the present study is to characterize the best outlet location that provides the greatest effective cooling in the blocks by maximizing the heat-elimination rate and decreasing the total temperature in the cavity. Obtained results showed that the variations of the air outlet position in the cavity and the Richardson number have major effects on the stream function and heat transfer.

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.

scholarly journals Three-dimensional numerical study of mixed convection within a ventilated cavity (Shape ‘ L ‘) crossed by a nanofluid under the effect of a magnetic field

2020 ◽  
Vol 307 ◽  
pp. 01027
Author(s):  
S. KHERROUBI ◽  
K. RAGUI ◽  
N. LABSI ◽  
Y.K. BENKAHLA ◽  
A. BOUTRA
Keyword(s):  
Magnetic Field ◽  
Mixed Convection ◽  
Volume Fraction ◽  
Numerical Study ◽  
Vertical Wall ◽  
Three Dimensional ◽  
Convection Heat Transfer ◽  
Left Wall ◽  
Ventilated Cavity ◽  
The Right

The present work is dedicated to the three-dimensional numerical study of mixed convection heat transfer, taking place within a ventilated cavity (of shape L) crossed by Cu-water nanofluid. The enclosure is subjected to the action of a magnetic field. The ventilation is assured by two openings of the same size. The cold flow enters by an opening practiced at the top of the left wall, and exits by another opening practiced at the bottom of the right vertical wall. All the cavity walls are maintained at the same temperature, superior to that of the entering flow, except the side walls which are considered as adiabatic. The control parameters are: the Reynolds number and the Hartmann number as well as the nanoparticles volume fraction.

Upward and downward conjugate mixed convection heat transfer in a partially porous cavity

2016 ◽  
Vol 26 (1) ◽  
pp. 159-188 ◽  
Author(s):  
Abderrahim Bourouis ◽  
Abdeslam Omara ◽  
Said Abboudi
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Mixed Convection ◽  
Transfer Rate ◽  
Vertical Wall ◽  
Thermal Conductivity Ratio ◽  
Conductivity Ratio ◽  
Content Type ◽  
Moving Wall ◽  
The Right

Purpose – The purpose of this paper is to provide a numerical study of conjugate heat transfer by mixed convection and conduction in a lid-driven enclosure with thick vertical porous layer. The effect of the relevant parameters: Richardson number (Ri=0.1, 1, 10) and thermal conductivity ratio (Rk=0.1, 1, 10, 100) are investigated. Design/methodology/approach – The studied system is a two dimensional lid-driven enclosure with thick vertical porous layer. The left vertical wall of the enclosure is allowed to move in its own plane at a constant velocity. The enclosure is heated from the right vertical wall isothermally. The left and the right vertical walls are isothermal but temperature of the outside of the right vertical wall is higher than that of the left vertical wall. Horizontal walls are insulated. The governing equations are solved by finite volume method and the SIMPLE algorithm. Findings – From the finding results, it is observed that: for the two studied cases, heat transfer rate along the hot wall is a decreasing function of thermal conductivity ratio irrespective of Richardson numbers contrary to the heat transfer rate along the fluid-porous layer interface which is an increasing function of thermal conductivity ratio. At forced convection dominant regime, the difference between heat transfer rate for upward and downward moving wall is insensitive to the thermal conductivity ratio. For downward moving wall, average Nusselt number is higher than that of upward moving wall. Practical implications – Some applications: building applications, furnace design, nuclear reactors, air solar collectors. Originality/value – From the bibliographic work and the authors’ knowledge, the conjugate mixed convection in lid-driven partially porous enclosures has not yet been investigated which motivates the present work that represent a continuation of the preceding investigations.

scholarly journals Mhd Mixed Convection in Copper-Water Nanofluid Filled Lid-Driven Square Cavity Containing Multiple Adiabatic Obstacles with Discrete Heating

2020 ◽  
Vol 25 (2) ◽  
pp. 57-74
Author(s):  
R.S.R. Gorla ◽  
S. Siddiqa ◽  
A.A. Hasan ◽  
T. Salah ◽  
A.M. Rashad
Keyword(s):  
Heat Source ◽  
Mixed Convection ◽  
Convection Flow ◽  
Square Cavity ◽  
Left Wall ◽  
Simpler Algorithm ◽  
Position Parameter ◽  
The Right ◽  
Volume Method ◽  
Good Agreement

AbstractThe objective of the present work is to investigate the influence of nanoparticles of copper within the base fluid (water) on magneto-hydrodynamic mixed-convection flow in a square cavity with internal generation. A control finite volume method and SIMPLER algorithm are used in the numerical calculations. The geometry is a lid-driven square cavity with four interior square adiabatic obstacles. A uniform heat source is located in a part of the left wall and a part of the right wall of the enclosure is maintained at cooler temperature while the remaining parts of the two walls are thermally insulated. Both the upper and bottom walls of the cavity are considered to be adiabatic. A comparison with previously published works shows a very good agreement. It is observed that the Richardson number, Ri, significantly alters the behavior of streamlines when increased from 0.1 to 100.0. Also, the heat source position parameter, D, significantly changes the pattern of isotherms and its strength shifted when D moves from 0.3 to 0.7.

Influence of Coil Inclined around Y Axis on Thermomagnetic Convection of Air in a Porous Cubic Enclosure under Zerogravity

2011 ◽  
Vol 354-355 ◽  
pp. 24-28 ◽  
Author(s):  
Chang Wei Jiang ◽  
Xian Feng Zhu ◽  
Er Shi ◽  
Zhen Zhou
Keyword(s):  
Heat Transfer ◽  
Magnetic Force ◽  
Vertical Wall ◽  
Simple Algorithm ◽  
Darcy Number ◽  
The Other ◽  
Governing Equations ◽  
Left Hand ◽  
Thermomagnetic Convection ◽  
Volume Method

Thermomagnetic convection of air in a porous cubic enclosure with a electric coil inclined around the Y axis is numerically investigated under zerogravity environment. The porous cubic enclosure is heated isothermally from left-hand side vertical wall and cooled isothermally from opposing wall while the other four walls are thermally insulated. The governing equations in primitive variables are discretized by the finite-volume method and solved by the SIMPLE algorithm. The results show that the overall heat transfer is enhanced gradually with the increase of magnetic force number and Darcy number. The resulted convection is symmetrical in terms of the angle at yeuler =0 when the range of inclination angle is from -90 to 90.

Heightened Thermal Convection as a Result of Splitting a Square Cavity Diagonally in Half

2005 ◽  
Vol 128 (3) ◽  
pp. 251-258 ◽  
Author(s):  
El Hassan Ridouane ◽  
Antonio Campo
Keyword(s):  
Vertical Wall ◽  
Maximum Error ◽  
Correlation Equation ◽  
Temperature Dependent ◽  
Square Cavity ◽  
Cavity System ◽  
The Mean ◽  
The Right ◽  
Volume Method ◽  
Rayleigh Numbers

This investigation addresses the thermogeometric performance of a two-square cavity system contrasted against a two-isosceles triangular cavity system, with an exactly equal heating segment and comparable cooling segment. When one square cavity is cut diagonally in half, it results in a pair of isosceles triangular cavities. The isosceles triangular cavity on the left is heated from the left vertical wall, the top wall is insulated, and the inclined wall is cold; the so-called HIC triangular cavity. The isosceles triangular cavity on the right is heated from the right vertical wall, the bottom wall is insulated, and the inclined wall is cold; the so-called HCI triangular cavity. It may be speculated that the two-isosceles triangular cavity system may find application in the miniaturization of electronic packaging severely constrained by space and/or weight. The finite volume method, accounting for temperature-dependent thermophysical properties of air, is employed to perform the computational analysis. Representative height-based Rayleigh numbers assume values up to 106 to avoid oscillations that occur at a Rayleigh number between RaH=2×106 and 2.2×106. Numerical results are reported for the velocity field, the temperature field, and the local and the mean convective coefficient along the heated vertical wall. Under a dominant conduction condition for RaH=103, the heat flux across the derived two-isosceles triangular system is 334% higher than its counterpart across the original two-square system. In contrast, for a dominant convection condition for RaH=106, this margin diminishes to 20%, but still constitutes a significant improvement. For the design of two-triangular cavity systems, a NuH correlation equation has been constructed yielding a maximum error of 2% at RaH=104.

Laminar Natural Convection in a Complicated Cavity With Spatially Variable Upper Wall Temperature

2003 ◽  
Author(s):  
Amaresh Dalal ◽  
Manab Kumar Das
Keyword(s):  
Natural Convection ◽  
Vertical Wall ◽  
Vertical Plane ◽  
Simple Algorithm ◽  
The Other ◽  
Heat Rejection ◽  
Laminar Natural Convection ◽  
The Right ◽  
Cold Walls ◽  
Spatially Varying

The study of natural convection inside a two-dimensional cavity with one and three undulations on the right vertical wall has been carried out where the top wall is heated by a spatially varying temperature and other three walls are cold walls. Non-orthogonal body-fitted coordinate system and SIMPLE algorithm with higher-order upwinding scheme are used. The streamline pattern shows two cells are formed separated at the middle vertical plane for both the configurations. The center of the cells is lifted upwards with increase in Ra. The heat rejection from the fluid to the right wall increases for the uppermost undulation whereas there is not much improvement of heat transfer for the other two in the three undulation case. For this particular configuration, the heat rejection increases with increase of Ra for the uppermost undulation and decreases with increase of Ra for the other two undulations. The overall improvement of heat rejection has been observed for three undulation case compared with one undulation case.

Natural Convection Cooling of an Array of Flush Mounted Discrete Heaters Inside a 3D Cavity

2017 ◽  
Vol 9 (3) ◽  
pp. 698-721 ◽  
Author(s):  
V. P. M. Senthil Nayaki ◽  
S. Saravanan ◽  
X. D. Niu ◽  
P. Kandaswamy
Keyword(s):  
Heat Transfer ◽  
Aspect Ratio ◽  
Vertical Wall ◽  
Three Dimensional ◽  
Heat Removal ◽  
Simple Algorithm ◽  
Nusselt Numbers ◽  
Flow And Heat Transfer ◽  
Cold Walls ◽  
Volume Method

AbstractAn investigation of natural convective flow and heat transfer inside a three dimensional rectangular cavity containing an array of discrete heat sources is carried out. The array consists of a row and columnwise regular arrangement of identical square shaped isoflux discrete heaters and is flush mounted on a vertical wall of the cavity. A symmetrical isothermal sink condition is maintained by cooling the cavity uniformly from either the opposite wall or the side walls or the top and bottom walls. The other walls of the cavity are maintained adiabatic. A finite volume method based on the SIMPLE algorithm and the power law scheme is used to solve the conservation equations. The parametric study covers the influence of pertinent parameters such as the Rayleigh number, the Prandtl number, side aspect ratio of the cavity and cavity heater ratio. A detailed fluid flow and heat transfer characteristics for the three cases are reported in terms of isothermal and velocity vector plots and Nusselt numbers. In general it is found that the overall heat transfer rate within the cavity for Ra=107 is maximum when the side aspect ratio of the cavity lies between 1.5 and 2. A more complex and peculiar flow pattern is observed in the presence of top and bottom cold walls which in turn introduces hot spots on the adiabatic walls. Their location and size are highly sensitive to the side aspect ratio of the cavity and hence offers more effective ways for passive heat removal.

Influence of Coil Inclined around X Axis on Thermomagnetic Convection of Air in a Porous Cubic Enclosure under Zerogravity

2011 ◽  
Vol 354-355 ◽  
pp. 174-178 ◽  
Author(s):  
Chang Wei Jiang ◽  
Ming Zhang ◽  
Xian Feng Zhu
Keyword(s):  
Inclination Angle ◽  
Magnetic Force ◽  
Vertical Wall ◽  
Simple Algorithm ◽  
Darcy Number ◽  
The Other ◽  
Governing Equations ◽  
Left Hand ◽  
Thermomagnetic Convection ◽  
Volume Method

Thermomagnetic convection of air in a porous cubic enclosure with an electric coil inclined around the X axis is numerically investigated under zerogravity environment. The porous cubic enclosure is heated isothermally from left-hand side vertical wall and cooled isothermally from opposing wall while the other four walls are thermally insulated. The governing equations in primitive variables are discretized by the finite-volume method and solved by the SIMPLE algorithm. The results show that the overall heat transfer is enhanced gradually with the increase of magnetic force number and Darcy number. The resulted convection is symmetrical in terms of the inclination angle at xeuler =45 when the range of inclination angle is from 0 to 90 .

Numerical analysis of mixed convection of different nanofluids in concentric annulus

2019 ◽  
Vol 29 (4) ◽  
pp. 1506-1525 ◽  
Author(s):  
Ahad Abedini ◽  
Saeed Emadoddin ◽  
Taher Armaghani
Keyword(s):  
Heat Transfer ◽  
Mixed Convection ◽  
Flow Pattern ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Volume Fraction ◽  
Convection Heat Transfer ◽  
Simple Algorithm ◽  
Content Type ◽  
Volume Method

Purpose This study aims to investigate the numerical analysis of mixed convection within the horizontal annulus in the presence of water-based fluid with nanoparticles of aluminum oxide, copper, silver and titanium oxide. Numerical solution is performed using a finite-volume method based on the SIMPLE algorithm, and the discretization of the equations is generally of the second order. Inner and outer cylinders have a constant temperature, and the inner cylinder temperature is higher than the outer one. The two cylinders can be rotated in both directions at a constant angular velocity. The effect of parameters such as Rayleigh, Richardson, Reynolds and the volume fraction of nanoparticles on heat transfer and flow pattern are investigated. The results show that the heat transfer rate increases with the increase of the Rayleigh number, as well as by increasing the volume fraction of the nanoparticles, the heat transfer rate increases, and this increase is about 8.25 per cent for 5 per cent volumetric fraction. Rotation of the cylinders reduces the overall heat transfer. Different directions of rotation have a great influence on the flow pattern and isotherms, and ultimately on heat transfer. The addition of nanoparticles does not have much effect on the flow pattern and isotherms, but it is quantitatively effective. The extracted results are in good agreement with previous works. Design/methodology/approach Studying mixed convection heat transfer in the horizontal annulus in the presence of a water-based fluid with aluminum oxide, copper, silver and titanium oxide nanoparticles is carried out quantitatively using a finite-volume method based on the SIMPLE algorithm. Findings Increasing the Rayleigh number increases the Nusselt number. Increasing the Richardson number increases heat transfer. Adding nanoparticles does not have much effect on the flow pattern but is effective quantitatively on heat transfer parameters. The addition of nanoparticles sometimes increases the heat transfer rate by about 8.25 per cent. In constant Rayleigh numbers, increasing the Reynolds number reduces heat transfer. The Rayleigh and Reynolds numbers greatly affect the isotherms and streamlines. In addition to the thermal conductivity of nanoparticles, the thermo-physical properties of nanoparticles has great effect in the formation of isotherms and streamlines and ultimately heat transfer. Originality/value Studying the effect of different direction of rotation on the isotherms and streamlines, as well as the comparison of different nanoparticles on mixed convection heat transfer in annulus.

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