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.

scholarly journals Unconfined laminar nanofluid flow and heat transfer around a rotating circular cylinder in the steady regime

2017 ◽  
Vol 38 (2) ◽  
pp. 3-20
Author(s):  
Rafik Bouakkaz ◽  
Fouzi Salhi ◽  
Yacine Khelili ◽  
Mohamed Quazzazi ◽  
Kamel Talbi
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Circular Cylinder ◽  
Rotation Rate ◽  
Volume Fraction ◽  
Steady Regime ◽  
Volume Fractions ◽  
Nusselt Numbers ◽  
Rotating Circular Cylinder ◽  
Flow And Heat Transfer

AbstractIn this work, steady flow-field and heat transfer through a copper- water nanofluid around a rotating circular cylinder with a constant nondimensional rotation rate α varying from 0 to 5 was investigated for Reynolds numbers of 5–40. Furthermore, the range of nanoparticle volume fractions considered is 0–5%. The effect of volume fraction of nanoparticles on the fluid flow and heat transfer characteristics are carried out by using a finite-volume method based commercial computational fluid dynamics solver. The variation of the local and the average Nusselt numbers with Reynolds number, volume fractions, and rotation rate are presented for the range of conditions. The average Nusselt number is found to decrease with increasing value of the rotation rate for the fixed value of the Reynolds number and volume fraction of nanoparticles. In addition, rotation can be used as a drag reduction technique.

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.

Measurement and Analysis of Laminar Heat Transfer Coefficients in Micro and Mini-Scale Ducts and Channels

2014 ◽  
Author(s):  
Y. S. Muzychka ◽  
M. Ghobadi
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Reynolds Numbers ◽  
Transfer Coefficients ◽  
Constant Wall Temperature ◽  
Fully Developed Flow ◽  
Transfer Rates ◽  
Heat Transfer Coefficients ◽  
Advantages And Disadvantages ◽  
Nusselt Numbers

Heat transfer in micro and mini-scale ducts and channels is considered. In particular, issues of thermal performance are considered in systems with constant wall temperature at low to moderate Reynolds numbers or small dimensional scales which lead to conditions characteristic of thermally fully developed flows or within the transition region leading to thermally fully developed flows. An analysis of two approaches to representing experimental data is given. One using the traditional Nusselt number and another using the dimensionless mean wall flux. Both approaches offer a number of advantages and disadvantages. In particular, it is shown that while good data can be obtained which agree with predicted heat transfer rates, the same data can be problematic if one desires a Nusselt number. Other issues such as boundary conditions pertaining to measuring thermally developing and fully developed flow Nusselt numbers are also discussed in detail.

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 and Pressure Drop Characteristics of Water in the Transitional Flow Regime of Horizontal Smooth Tubes at Constant Wall Temperature

2010 ◽  
Author(s):  
J. P. Meyer ◽  
A. Du Preez
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Flow Regime ◽  
Wall Temperature ◽  
Reynolds Numbers ◽  
Transitional Flow ◽  
Maximum Efficiency ◽  
Constant Wall Temperature ◽  
Pressure Losses ◽  
Nusselt Numbers

Owing to design limitations, heat exchangers are frequently forced to operate in the transitional flow regime, however, there exists no accurate measurements for both heat transfer and pressure drop in this region. In order to optimize a heat exchanger for maximum efficiency and minimum pressure losses, it is required to design it for the transitional flow regime. Therefore, the purpose of this study is to obtain accurate Nusselt numbers and pressure drop coefficients for water flowing through a horizontal smooth tube with a constant wall temperature. Heat transfer and pressure drop measurements were conducted on a 5.33 mm tube at Reynolds numbers ranging from 1 000 to 5 000.

Heat Transfer Measurements and Numerical Simulations in the Cooling of a Circular Cylinder by a Slot Jet of Air

2003 ◽  
Author(s):  
F. Gori ◽  
I. Petracci
Keyword(s):  
Heat Transfer ◽  
Circular Cylinder ◽  
Numerical Simulations ◽  
Convective Heat Transfer ◽  
Reynolds Numbers ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Nusselt Numbers ◽  
Commercial Code ◽  
Convective Heat Transfer Coefficients

The present paper reports heat transfer measurements on a circular cylinder, electrically heated, and cooled by a slot jet of air. The diameter of the cylinder is equal to the slot height. Temperature measurements in five positions along the circumference of the circular cylinder, allow the evaluation of the convective heat transfer coefficients or Nusselt numbers at several Reynolds numbers. The Nusselt numbers are compared with the corresponding results in uniform flow around a circular cylinder. The experiments have been performed at several distances from the slot jet exit and different Reynolds numbers. Numerical simulations have been carried out with a commercial code.

Pulsating Jets Cooling Circular Cylinders

2003 ◽  
Author(s):  
F. Gori ◽  
G. Pacchiarotti ◽  
I. Petracci
Keyword(s):  
Heat Transfer ◽  
Wind Tunnel ◽  
Circular Cylinder ◽  
Rotating Disk ◽  
Reynolds Numbers ◽  
Circular Cylinders ◽  
Nusselt Numbers ◽  
Experimental Heat ◽  
Experimental Heat Transfer ◽  
Pulsating Jets

The paper presents experimental heat transfer results on a circular cylinder cooled by a pulsating slot jet of air. The jet is generated by a new small wind tunnel, designed for flows with low turbulence intensities. The pulsation of the jet is obtained with the introduction of a rotating disk, divided in sectors, between the exit of the slot and the cylinder to be cooled. The disk can rotate at several frequencies. Local and average Nusselt numbers have been measured at several Reynolds numbers and distances from the slot exit. The heat transfer results are dependent on the frequency of the pulsation. The position of the cylinder, which maximizes the heat transfer, is compared to the case of a stationary jet.

Heat Transfer in a Surfactant Drag-Reducing Solution—A Comparison With Predictions for Laminar Flow

2005 ◽  
Vol 128 (6) ◽  
pp. 557-563 ◽  
Author(s):  
Paul L. Sears ◽  
Libing Yang
Keyword(s):  
Heat Transfer ◽  
Laminar Flow ◽  
Reynolds Numbers ◽  
High Heat ◽  
High Heat Flux ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Nusselt Numbers ◽  
Drag Reducing Additive ◽  
Good Agreement

Heat transfer coefficients were measured for a solution of surfactant drag-reducing additive in the entrance region of a uniformly heated horizontal cylindrical pipe with Reynolds numbers from 25,000 to 140,000 and temperatures from 30to70°C. In the absence of circumferential buoyancy effects, the measured Nusselt numbers were found to be in good agreement with theoretical results for laminar flow. Buoyancy effects, manifested as substantially higher Nusselt numbers, were seen in experiments carried out at high heat flux.

Local Swirl Chamber Heat Transfer and Flow Structure at Different Reynolds Numbers

1999 ◽  
Vol 122 (2) ◽  
pp. 375-385 ◽  
Author(s):  
C. R. Hedlund ◽  
P. M. Ligrani
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Flow Structure ◽  
Flow Behavior ◽  
Turbine Blades ◽  
Reynolds Numbers ◽  
Local Flow ◽  
Flux Boundary Condition ◽  
Nusselt Numbers ◽  
Swirl Chamber

Local flow behavior and heat transfer results are presented from two swirl chambers, which model passages used to cool the leading edges of turbine blades in gas turbine engines. Flow results are obtained in an isothermal swirl chamber. Surface Nusselt number distributions are measured in a second swirl chamber (with a constant wall heat flux boundary condition) using infrared thermography in conjunction with thermocouples, energy balances, and in situ calibration procedures. In both cases, Reynolds numbers Re based on inlet duct characteristics range from 6000 to about 20,000. Bulk helical flow is produced in each chamber by two inlets, which are tangent to the swirl chamber circumference. Important changes to local and globally averaged surface Nusselt numbers, instantaneous flow structure from flow visualizations, and distributions of static pressure, total pressure, and circumferential velocity are observed throughout the swirl chambers as the Reynolds number increases. Of particular importance are increases of local surface Nusselt numbers (as well as ones globally averaged over the entire swirl chamber surface) with increasing Reynolds number. These are tied to increased advection, as well as important changes to vortex characteristics near the concave surfaces of the swirl chambers. Higher Re also give larger axial components of velocity, and increased turning of the flow from each inlet, which gives Go¨rtler vortex pair trajectories greater skewness as they are advected downstream of each inlet. [S0889-504X(00)00502-X]

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.

Sign in / Sign up

Export Citation Format

Share Document