scholarly journals Influence of CuO nanoparticles in enhancing the overall heat transfer around a square cylinder

10.30544/435 ◽  
2019 ◽  
Vol 25 (3) ◽  
pp. 225-236
Author(s):  
Rafik Bouakkaz ◽  
Yacine Khelili ◽  
Aliouali Abdelouahed
Keyword(s):  
Heat Transfer ◽  
Particle Diameter ◽  
Reynolds Numbers ◽  
Square Cylinder ◽  
Particle Volume ◽  
Volume Fractions ◽  
Nusselt Numbers ◽  
Flow And Heat Transfer ◽  
Volume Method ◽  
Opposing Effect

In this study, steady flow and heat transfer through a copper–water nanofluid around a square cylinder was investigated numerically by using a finite-volume method for Reynolds numbers of 10-40. Furthermore, the range of nanoparticle volume fractions () considered is 0 ≤  ≤ 0.04, with three different nanoparticle diameters dnp = 30, 60 and 90 nm. The variation of the local and the average Nusselt numbers with Reynolds number, and volume fractions are presented for the range of above conditions. The averaged Nusselt number showed clear enhancement comparing with the base fluids. This enhancement is more apparent in flows with higher particle volume concentration, whereas the particle diameter imposes an opposing effect on the heat transfer characteristics.

scholarly journals Numerical investigation of fluid flow and heat transfer around a circular cylinder utilizing nanofluid for different thermal boundary condition in the steady regime

10.30544/292 ◽  
2017 ◽  
Vol 23 (2) ◽  
pp. 131-141
Author(s):  
Rafik Bouakkaz ◽  
F. Salhi ◽  
Y. Khelili ◽  
M. Ouazzazi ◽  
K. Talbi
Keyword(s):  
Heat Transfer ◽  
Circular Cylinder ◽  
Reynolds Numbers ◽  
Uniform Heat Flux ◽  
Constant Wall Temperature ◽  
Steady Regime ◽  
Volume Fractions ◽  
Thermal Boundary Conditions ◽  
Nusselt Numbers ◽  
Volume Method

In this work, steady flow-field and heat transfer through a copper–water nanofluid around a circular cylinder, under the influence of both the standard thermal boundary conditions i.e. uniform heat flux (UHF) and constant wall temperature (CWT) was investigated numerically by using a finite-volume method for Reynolds numbers of 10 to 40. Furthermore, the range of nanoparticle volume fractions (φ) considered is 0 ≤ φ ≤ 5%. The variation of the local and the average Nusselt numbers with Reynolds number, and volume fractions are presented for the range of conditions. The average Nusselt number is found to increase with increasing the nanoparticle volume fractions.

A Numerical Study of Heat Transfer and Flow Structure in Channels With Miniature V Rib-Dimple Hybrid Structure on One Wall

2018 ◽  
Author(s):  
Peng Zhang ◽  
Yu Rao ◽  
Yanlin Li
Keyword(s):  
Heat Transfer ◽  
Turbulent Flow ◽  
Numerical Simulations ◽  
Numerical Study ◽  
Reynolds Numbers ◽  
Hybrid Structure ◽  
Transfer Enhancement ◽  
Nusselt Numbers ◽  
Flow And Heat Transfer ◽  
Flow Mixing

This paper presents a numerical study on turbulent flow and heat transfer in the channels with a novel hybrid cooling structure with miniature V-shaped ribs and dimples on one wall. The heat transfer characteristics, pressure loss and turbulent flow structures in the channels with the rib-dimples with three different rib heights of 0.6 mm, 1.0 mm and 1.5 mm are obtained for the Reynolds numbers ranging from 18,700 to 60,000 by numerical simulations, which are also compared with counterpart of a pure dimpled and pure V ribbed channel. The results show that the overall Nusselt numbers of the V rib-dimple channel with the rib height of 1.5 mm is up to 70% higher than that of the channels with pure dimples. The numerical simulations show that the arrangement of the miniature V rib upstream each dimple induces complex secondary flow near the wall and generates downwashing vortices, which intensifies the flow mixing and turbulent kinetic energy in the dimple, resulting in significant improvement in heat transfer enhancement and uniformness.

scholarly journals Effect of Rayleigh Number on Internal Eccentricity in a Heated Horizontal Elliptical Cylinder to its Coaxial Square Enclosure

2020 ◽  
Vol 25 (3) ◽  
pp. 17-29
Author(s):  
Abdelkrim Bouras ◽  
Djedid Taloub ◽  
Zied Driss
Keyword(s):  
Heat Transfer ◽  
Rayleigh Number ◽  
Outer Cylinder ◽  
Boussinesq Approximation ◽  
Square Enclosure ◽  
Nusselt Numbers ◽  
Flow And Heat Transfer ◽  
Commercial Code ◽  
Volume Method ◽  
Rayleigh Numbers

AbstractThis paper deals with numerical investigation of a natural convective flow in a horizontal annular space between a heated square inner cylinder and a cold elliptical outer cylinder with a Newtonian fluid. Uniform temperatures are imposed along walls of the enclosure. The governing equations of the problem were solved numerically by the commercial code Fluent, based on the finite volume method and the Boussinesq approximation. The effects of Geometry Ratio GR and Rayleigh numbers on fluid flow and heat transfer performance are investigated. The Rayleigh number is varied from 103 to 106. Throughout the study the relevant results are presented in terms of isotherms, and streamlines. From the results, we found that the increase in the Geometry Ratio B leads to an increase of the heat transfer coefficient. The heat transfer rate in the annulus is translated in terms of the average Nusselt numbers along the enclosure’s sides. Tecplot 7 program was used to plot the curves which cleared these relations and isotherms and streamlines which illustrate the behavior of air through the channel and its variation with other parameters. The results for the streamlines, isotherms, local and average Nusselt numbers average Nusselt numbers are compared with previous works and show good agreement.

Heat Transfer in a “Cover-Plate” Preswirl Rotating-Disk System

1999 ◽  
Vol 121 (2) ◽  
pp. 249-256 ◽  
Author(s):  
R. Pilbrow ◽  
H. Karabay ◽  
M. Wilson ◽  
J. M. Owen
Keyword(s):  
Heat Transfer ◽  
Rotating Disk ◽  
Reynolds Numbers ◽  
Turbine Disk ◽  
Cover Plate ◽  
Blade Cooling ◽  
Nusselt Numbers ◽  
Flow And Heat Transfer ◽  
Cooling Air ◽  
Plate System

In most gas turbines, blade-cooling air is supplied from stationary preswirl nozzles that swirl the air in the direction of rotation of the turbine disk. In the “cover-plate” system, the preswirl nozzles are located radially inward of the blade-cooling holes in the disk, and the swirling airflows radially outward in the cavity between the disk and a cover-plate attached to it. In this combined computational and experimental paper, an axisymmetric elliptic solver, incorporating the Launder–Sharma and the Morse low-Reynolds-number k–ε turbulence models, is used to compute the flow and heat transfer. The computed Nusselt numbers for the heated “turbine disk” are compared with measured values obtained from a rotating-disk rig. Comparisons are presented, for a wide range of coolant flow rates, for rotational Reynolds numbers in the range 0.5 X 106 to 1.5 X 106, and for 0.9 < βp < 3.1, where βp is the preswirl ratio (or ratio of the tangential component of velocity of the cooling air at inlet to the system to that of the disk). Agreement between the computed and measured Nusselt numbers is reasonably good, particularly at the larger Reynolds numbers. A simplified numerical simulation is also conducted to show the effect of the swirl ratio and the other flow parameters on the flow and heat transfer in the cover-plate system.

Periodic Fluid Flow and Heat Transfer in a Square Cavity Due to an Insulated or Isothermal Rotating Cylinder

2009 ◽  
Vol 131 (11) ◽  
Author(s):  
Y.-C. Shih ◽  
J. M. Khodadadi ◽  
K.-H. Weng ◽  
A. Ahmed
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Convection Heat Transfer ◽  
Reynolds Numbers ◽  
Rotating Cylinder ◽  
Flow Fields ◽  
Square Cavity ◽  
Nusselt Numbers ◽  
Flow And Heat Transfer ◽  
Rotating Objects

The periodic state of laminar flow and heat transfer due to an insulated or isothermal rotating cylinder object in a square cavity is investigated computationally. A finite-volume-based computational methodology utilizing primitive variables is used. Various rotating objects (circle, square, and equilateral triangle) with different sizes are placed in the middle of a square cavity. A combination of a fixed computational grid and a sliding mesh was utilized for the square and triangle shapes. For the insulated and isothermal objects, the cavity is maintained as differentially heated and isothermal enclosures, respectively. Natural convection heat transfer is neglected. For a given shape of the object and a constant angular velocity, a range of rotating Reynolds numbers are covered for a Pr=5 fluid. The Reynolds numbers were selected so that the flow fields are not generally affected by the Taylor instabilities (Ta<1750). The periodic flow field, the interaction of the rotating objects with the recirculating vortices at the four corners, and the periodic channeling effect of the traversing vertices are clearly elucidated. The simulations of the dynamic flow fields were confirmed against experimental data obtained by particle image velocimetry. The corresponding thermal fields in relation to the evolving flow patterns and the skewness of the temperature contours in comparison to the conduction-only case were discussed. The skewness is observed to become more marked as the Reynolds number is lowered. Transient variations of the average Nusselt numbers of the respective systems show that for high Re numbers, a quasiperiodic behavior due to the onset of the Taylor instabilities is dominant, whereas for low Re numbers, periodicity of the system is clearly observed. Time-integrated average Nusselt numbers of the insulated and isothermal object systems were correlated with the rotational Reynolds number and shape of the object. For high Re numbers, the performance of the system is independent of the shape of the object. On the other hand, with lowering of the hydraulic diameter (i.e., bigger objects), the triangle and the circle exhibit the highest and lowest heat transfers, respectively. High intensity of the periodic channeling and not its frequency is identified as the cause of the observed enhancement.

Heat Transfer in a “Cover-Plate” Pre-Swirl Rotating-Disc System

1998 ◽  
Author(s):  
Robert Pilbrow ◽  
Hasan Karabay ◽  
Michael Wilson ◽  
J. Michael Owen
Keyword(s):  
Heat Transfer ◽  
Reynolds Numbers ◽  
Cover Plate ◽  
Swirl Ratio ◽  
Rotating Disc ◽  
Blade Cooling ◽  
Nusselt Numbers ◽  
Flow And Heat Transfer ◽  
Turbine Disc ◽  
Cooling Air

In most gas turbines, blade-cooling air is supplied from stationary pre-swirl nozzles that swirl the air in the direction of rotation of the turbine disc. In the “cover-plate” system, the pre-swirl nozzles are located radially inward of the blade-cooling holes in the disc, and the swirling air flows radially outwards in the cavity between the disc and a cover-plate attached to it. In this combined computational and experimental paper, an axisymmetric elliptic solver, incorporating the Launder-Sharma and the Morse low-Reynolds-number k-ε turbulence models, is used to compute the flow and heat transfer. The computed Nusselt numbers for the heated “turbine disc” are compared with measured values obtained from a rotating-disc rig. Comparisons are presented, for a wide range of coolant flow rates, for rotational Reynolds numbers in the range 0.5 × 106 to 1.5 × 106, and for 0.9 < βp < 3.1, where βp is the pre-swirl ratio (or ratio of the tangential component of velocity of the cooling air at inlet to the system to that of the disc). Agreement between the computed and measured Nusselt numbers is reasonably good, particularly at the larger Reynolds numbers. A simplified numerical simulation is also conducted to show the effect of the swirl ratio and the other flow parameters on the flow and heat transfer in the cover-plate system.

Streamwise Flow and Heat Transfer Distributions for Jet Array Impingement With Crossflow

1981 ◽  
Author(s):  
L. W. Florschuetz ◽  
C. R. Truman ◽  
D. E. Metzger
Keyword(s):  
Heat Transfer ◽  
Flow Distribution ◽  
Reynolds Numbers ◽  
Geometric Parameters ◽  
Channel Height ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Nusselt Numbers ◽  
Flow And Heat Transfer ◽  
Circular Jets

Two-dimensional arrays of circular jets of air impinging on a heat transfer surface parallel to the jet orifice plate are considered. The air, after inpingement, is constrained to exit in a single direction along the channel formed by the surface and the jet plate. The downstream jets are subjected to a crossflow originating from the upstream jets. Experimental and theoretical results obtained for streamwise distributions of jet and crossflow velocities are presented and compared. Measured Nusselt numbers resolved to one streamwise hole spacing are correlated with individual spanwise row jet Reynolds numbers and crossflow-to-jet velocity ratios. Correlations are presented for both inline and staggered hole patterns including effects of geometric parameters: streamwise hole spacing, spanwise hole spacing, and channel height, normalized by hole diameter. The physical mechanisms influencing heat transfer coefficients as a function of flow distribution and geometric parameters are also discussed.

scholarly journals A Complementary Experimental and Numerical Study of the Flow and Heat Transfer in Offset Strip-Fin Heat Exchangers

1998 ◽  
Vol 120 (3) ◽  
pp. 690-698 ◽  
Author(s):  
N. C. DeJong ◽  
L. W. Zhang ◽  
A. M. Jacobi ◽  
S. Balachandar ◽  
D. K. Tafti
Keyword(s):  
Heat Transfer ◽  
Complex Geometry ◽  
Numerical Study ◽  
Reynolds Numbers ◽  
Numerical Results ◽  
Thermal Boundary Conditions ◽  
Nusselt Numbers ◽  
Flow And Heat Transfer ◽  
Unsteady Numerical Simulation ◽  
Offset Strip Fin

A detailed analysis of experimental and numerical results for flow and heat transfer in similar offset strip-fin geometries is presented. Surface-average heat transfer and pressure drop, local Nusselt numbers and skin friction coefficients on the fin surface, instantaneous flow structures, and local time-averaged velocity profiles are contrasted for a range of Reynolds numbers using both prior and new experimental and numerical results. This contrast verifies that a two-dimensional unsteady numerical simulation captures the important features of the flow and heat transfer for a range of conditions. However, flow three-dimensionality appears to become important for Reynolds numbers greater than about 1300, and thermal boundary conditions are important for Reynolds numbers below 1000. The results indicate that boundary layer development, flow separation and reattachment, wake formation, and vortex shedding are all important in this complex geometry.

Heat Transfer Improvement in a Square Duct with Diagonal Inclined Ribs

2014 ◽  
Vol 931-932 ◽  
pp. 1144-1148
Author(s):  
Supattarachai Suwannapan ◽  
Ratsak Poomsalood ◽  
Pongjet Promvonge ◽  
Withada Jedsadaratanachai ◽  
Thitipat Limkul
Keyword(s):  
Heat Transfer ◽  
Friction Factor ◽  
Numerical Study ◽  
Simple Algorithm ◽  
Reynolds Numbers ◽  
Square Duct ◽  
Flow And Heat Transfer ◽  
Pitch Ratio ◽  
Volume Method ◽  
Heat Transfer Improvement

This research presents a numerical study of turbulent periodic flow and heat transfer in threedimensional isothermalfluxed square duct with diagonal inclined rib inserted. The fluid flow and heat transfer characteristics are presented for Reynolds numbers in the range of 4000 to 20,000. The computations based on the finite volume method, and the SIMPLE algorithm has been implemented. Effects of rib pitch ratios (0.5 to 2) at a single blockage ratio of 0.2 and attack angle of 60o on heat transfer and friction factor in the duct are examined and their results of the inclined rib are also compared with those of the smooth duct. It is found that the inclined rib provides higher heat transfer rate and friction factor than the smooth duct for all cases. In addition, the decreasing of the pitch ratio leads to the rise in the Nusselt number and friction factor.

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