Study on Flow Structure Behind Multiple Circular Cylinders in a Tandem Arrangement Under the Effect of Magnetic Field

CFD Letters ◽  
2021 ◽  
Vol 13 (11) ◽  
pp. 126-136
Author(s):  
Nur Marissa Kamarul Baharin ◽  
Mohd Azan Mohammed Sapardi ◽  
Ahmad Hussein Abdul Hamid ◽  
Syed Noh Syed Abu Bakar
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Flow Structure ◽  
Critical Reynolds Number ◽  
Nuclear Fusion ◽  
Fusion Reaction ◽  
Transfer Efficiency ◽  
Heat Transfer Efficiency

The fast-moving technologies and the increasing rate of growth population indicates that the demand for energy will continue to be spiking and prominent in the discussion of the upcoming future. Therefore, to cater to the need for sustainable and clean energy, the idea of nuclear fusion is proposed and studied. Because the nuclear fusion reaction happens at a high temperature, the concept of magnetic field is adapted to the nuclear or plasma fusion reaction. The energy will be harnessed inside a blanket module of the fusion reaction plant. However, the presence of the magnetic field affects the fluid flow inside the blanket module where it reduces the heat transfer efficiency in the channel. This research examines the flow structure behind multiple bluff bodies arranged in tandem in a channel under the influence of a magnetic field with the aim to increase the heat transfer efficiency inside the channel. The effect of gap ratio, G/h = [1-2.4] and Hartmann friction parameter, H = [0-800], were analysed to determine the critical Reynolds number and Nusselt number. It was found that the presence of the downstream cylinder with gap ratios, G/h = 1.2, 1.4 and 1.6, causes the flow to be unsteady at a lower Reynolds number compared to those of a single cylinder. The multiple cylinders proved to increase the Nusselt number. Increasing the Hartmann friction parameter increases the critical Reynolds number and decreases the Nusselt number.

Viscous Dissipation and Variable Properties Effect on Two Dimensional Conjugate Heat Transfer of Nanofluids in Microchannels

2011 ◽  
Author(s):  
A. Ramiar ◽  
A. A. Ranjbar
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Viscous Dissipation ◽  
Conjugate Heat Transfer ◽  
Energy Equation ◽  
Critical Reynolds Number ◽  
Two Dimensional ◽  
Variable Properties ◽  
Enhance Heat Transfer

Laminar two dimensional forced convective heat transfer of Al2O3–water nanofluid in a horizontal microchannel has been studied numerically, considering axial conduction, viscous dissipation and variable properties effects. The existing criteria in the literature for considering viscous dissipation in energy equation are compared for different cases and the most proper one is applied for the rest of the paper. The results showed that nanoparticles enhance heat transfer characteristics of the channel and inversely, viscous dissipation causes the Nusselt number and friction factor to decrease. The viscous dissipation effect may be emphasized by increasing Reynolds number and decreased by raising the exerted heat flux. Also, it was found that there is a critical Reynolds number below which the average Nusselt number of the nanofluid changes abnormally with Reynolds number as a result of variable properties effect.

Numerical simulation of mixed convection in a two-sided lid-driven square cavity with four inner cylinders based on diamond arrays

2020 ◽  
pp. 2150009
Author(s):  
Guyue Tang ◽  
Qin Lou ◽  
Ling Li
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Mixed Convection ◽  
Thermal Characteristics ◽  
Equation Model ◽  
Transfer Efficiency ◽  
Square Cavity ◽  
Left Wall ◽  
Heat Transfer Efficiency ◽  
Left And Right

The hydrodynamics and thermal characteristics due to mixed convection in a vertical two-sided lid-driven differentially square cavity containing four hot cylinders in a diamond array are investigated by the lattice Boltzmann equation model. The moving walls of the cavity are cold while the others are adiabatic. The flow in the cavity is driven by both the temperature difference and the moving vertical walls. The influence of different flow governing parameters, including the direction of the moving walls (the left wall moves up and the right wall moves down (Case I), both the left and right walls are moving upward (Case II), both the left and right walls are moving downwards (Case III)), the distance between neighboring cylinders [Formula: see text] ([Formula: see text]), and the Richardson number [Formula: see text] ([Formula: see text]) on the fluid flow and heat transfer are investigated with the Reynolds number in the range of [Formula: see text], the Grashof number of [Formula: see text] and the Prandtl number of [Formula: see text]. Flow and thermal performances in the cavity are analyzed in detail by considering the streamlines and isotherms profiles, the average Nusselt number, as well as the total Nusselt number. It is found that the heat transfer efficiency is highest when [Formula: see text] for the cases of the walls moving in the opposite direction. When the walls move in the same directions, the heat transfer efficiency obtained by [Formula: see text] is maximum among the considered values of [Formula: see text]. On the other hand, compared with the cases of [Formula: see text] and [Formula: see text], the cylinder positions corresponding to the largest and the smallest Nusselt numbers are very sensitive to the moving direction of the walls for [Formula: see text]. Moreover, the results also show that in terms of the value of Nusselt number and the stability the case of both walls moving downwards works well. Besides, the effect of the distance between neighboring cylinders is also discussed, it is found that increasing or decreasing the spacing between cylinders could enhance heat transfer to different degrees for the range of [Formula: see text] number considered. Finally, the empirical relationships among [Formula: see text], [Formula: see text], and the spacing between the cylinders ([Formula: see text]) are given, and predictive results match with the computed values very well.

scholarly journals Improvement of cooling performance of hybrid nanofluids in a heated pipe applying annular magnets

2021 ◽  
Author(s):  
Guolong Li ◽  
Jin Wang ◽  
Hongxing Zheng ◽  
Gongnan Xie ◽  
Bengt Sundén
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Carbon Nanotubes ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Volume Fraction ◽  
Circular Tube ◽  
Hybrid Nanofluid ◽  
Inner Diameter ◽  
Hybrid Nanofluids

AbstractIn this paper, convective heat transfer of Fe3O4–carbon nanotubes (CNTs) hybrid nanofluid was studied in a horizontal small circular tube under influence of annular magnets. The pipe has an inner diameter of 3 mm and a length of 1.2 m. Heat transfer characteristics of the Fe3O4–water nanofluid were examined for many parameters, such as nanoparticle volume fraction in the range of 0.4–1.2% and Reynolds number in the range of 476–996. In order to increase the thermal conductivity of the Fe3O4–water nanofluid, carbon nanotubes with 0.12–0.48% volume fraction were added into the nanofluid. It was observed that for the Fe3O4–CNTs–water nanofluid with 1.44% volume fraction and under a magnetic field, the maximal local Nusselt number at the Reynolds number 996 increased by 61.54% compared with without a magnetic field. Results also show that compared with the deionized water, the maximal enhancements of the average Nusselt number are 67.9 and 20.89% for the Fe3O4–CNTs–water nanofluid with and without magnetic field, respectively.

scholarly journals LBM Analysis of Micro-Convection in MHD Nanofluid Flow

2017 ◽  
Vol 63 (7-8) ◽  
pp. 426 ◽  
Author(s):  
Arjun Kozhikkatil Sunil ◽  
Rakesh Kumar
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Rayleigh Number ◽  
Field Strength ◽  
Magnetic Field Strength ◽  
Temperature Jump ◽  
Volume Fraction ◽  
Slip Coefficient

The lattice Boltzmann-Bhatnagar-Gross-Krook method was used to simulate Al2O3-water nanofluid to find the effects of Reynolds, Rayleigh and Hartmann numbers, slip coefficient, nanoparticle volume fraction and axial distance on forced convection heat transfer in MATLAB. The ranges of studied Reynolds number, Rayleigh number, magnetic field strength, nanoparticle volume concentration and slip coefficient include 200 ≤ Re ≤ 4000; 103 ≤ Ra ≤ 106; 0 ≤ Ha 90; 0 ≤ φ ≤ 2%; 0.005 ≤ B ≤ 0.02, respectively. The results show that increasing Reynolds number and nanoparticle volume fractions improve heat transfer in the 2D microtube under laminar, turbulent, slip and temperature jump boundary conditions. Decreasing the values of slip coefficient decreases the temperature jump and enhances the Nusselt number. A critical value for the Rayleigh number (105) and magnetic field strength (Ha 10) exists, at which the impacts of the solid volume fraction and slip coefficient effects are the most pronounced. The pressure drop shows a similar type of enhancement in magnitude, as observed in the case of the Nusselt number. However, application of nanofluids for low Reynolds numbers is more beneficial, and the effect of volume fractions are more pronounced in comparison to slip coefficient, though the effects are marginal.

scholarly journals CONVECTIVE HEAT TRANSFER ON STENOSED BLOOD FLOW THROUGH PERMEABLE MICROCIRCULATION IN THE PRESENCE OF A MAGNETIC FIELD

2020 ◽  
Author(s):  
Alana Sankar ◽  
Sreedhara Rao Gunakala ◽  
Donna Comissiong
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Reynolds Number ◽  
Blood Flow ◽  
Nusselt Number ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Hartmann Number ◽  
Darcy Number ◽  
Flow Through

Blood flow through permeable microcirculation in the presence of a composite stenosis, an external magnetic field and convective heat transfer was examined. A two-layered model for the blood consisting of a fluid-particle suspension in the core region with a peripheral cell-free plasma layer was used. The proposed system of equations was solved and plots were generated. In the presence of permeable walls, an external magnetic field and convective heat transfer, the temperature of the blood, friction-factor Reynolds number and Nusselt number were investigated. The temperature of the blood increased when the Hartmann number increased, Darcy number increased, haematocrit level increased or the peripheral layer thinned. The friction-factor Reynolds number product increased as the haematocrit, Hartmann number, stenosis height or Darcy number increased. The Nusselt number decreased as the Hartmann number, haematocrit, stenosis height or Darcy number increased. These results were interpreted in terms of the physical situation. This study aids in understanding the effects of wall permeability, a magnetic field and the presence of heat transfer on different diseased arterial systems in the future.

scholarly journals Steady interaction of a turbulent plane jet with a rectangular heated cavity

2016 ◽  
Vol 20 (5) ◽  
pp. 1485-1498
Author(s):  
Farida Iachachene ◽  
Amina Mataoui ◽  
Yacine Halouane
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Flow Structure ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Heated Wall ◽  
Turbulent Heat Transfer ◽  
Turbulent Heat ◽  
Potential Core

Turbulent heat transfer between a confined jet flowing in a hot rectangular cavity is studied numerically by finite volume method using the k-w SST one point closure turbulence model. The location of the jet inside the cavity is chosen so that the flow is in the non-oscillation regime. The flow structure is described for different jet-to-bottom-wall distances. A parametrical study was conducted to identify the influence of the jet exit location and the Reynolds number on the heat transfer coefficient. The parameters of this study are: the jet exit Reynolds number (Re, 1560< Re <33333), the temperature difference between the cavity heated wall and the jet exit (DT=60?C) and the jet location inside the cavity (Lf, 2? Lf? 10 and Lh 2.5<Lh?10). The Nusselt number increased and attained its maximum value at the stagnation points and then decreased. The flow structure is found in good agreement with the available experimental data. The maximum local heat transfer between the cavity walls and the flow occurs at the potential core end. The ratio between the stagnation point Nusselt numbers of the cavity bottom (NuB0) to the maximum Nusselt number on the lateral cavity wall (NuLmax) decreased with the Reynolds number for all considered impinging distances. For a given lateral confinement, the stagnation Nusselt number of the asymmetrical interaction Lh?10 is almost equal to that of the symmetrical interaction Lh=10.

Spatially-Resolved Heat Transfer and Flow Structure in a Rectangular Channel With 45° Angled Rib Turbulators

2002 ◽  
Author(s):  
G. I. Mahmood ◽  
P. M. Ligrani ◽  
S. Y. Won
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Flow Structure ◽  
Channel Cross Section ◽  
Cross Sectional ◽  
Spatially Resolved ◽  
Nusselt Numbers ◽  
Smooth Channel ◽  
Rib Turbulators

Spatially-resolved Nusselt numbers and flow structure are presented for a stationary channel with an aspect ratio of 4 and angled rib turbulators inclined at 45° with perpendicular orientations on two opposite surfaces. The flow structure results include time-averaged distributions of streamwise velocity and total pressure, surveyed over flow cross-sectional planes, as well as flow visualization images and friction factors. Results are given at different Reynolds numbers based on channel height from 270 to 90,000. The ratio of rib height to hydraulic diameter is .078, the rib pitch-to-height ratio is 10, and the blockage provided by the ribs is 25 percent of the channel cross-sectional area. Spatially-resolved local Nusselt numbers are highest on tops of the rib turbulators, with lower magnitudes on flat surfaces between the ribs, where regions of flow separation and shear layer re-attachment have pronounced influences on local surface heat transfer behavior. Also important are intense, highly unsteady secondary flows and vortex pairs, which increase secondary advection and turbulent transport over the entire channel cross-section. The resulting augmented local and spatially-averaged Nusselt number ratios (rib turbulator Nusselt numbers normalized by values measured in a smooth channel) generally increase on the rib tops as Reynolds number increases. Nusselt number ratios decrease on the flat regions away from the ribs, especially at locations just downstream of the ribs, as Reynolds number increases. Globally-averaged Nusselt number ratios vary from 3.36 to 2.82 as Reynolds number increases from 10,000 to 90,000. Thermal performance parameters also decrease somewhat as Reynolds number increases over this range, with values in approximate agreement with, or slightly higher than 60° continuous rib data measured by other investigators in a square channel.

scholarly journals Design and Development of Innovative Steam Injection for High-Temperature Short-Time Liquid Foods

Processes ◽  
2022 ◽  
Vol 10 (1) ◽  
pp. 161
Author(s):  
Wilasinee Sangsom ◽  
Chouw Inprasit
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Steam Injection ◽  
Transfer Efficiency ◽  
Optimal Conditions ◽  
Steam Temperature ◽  
Pineapple Juice ◽  
Heat Transfer Efficiency ◽  
High Temperature Short Time ◽  
Circular Holes

Jet impingement has been effective in reducing the process time and improvement of product quality in various industrial applications, such as textile and paper drying, electronic cooling, glass quenching and food processing. The current work applied innovative steam injection to liquid food continuous sterilization. The multiple impingement jets of steam and product came together in the impingement tank. The effects were investigated on the Reynolds number, steam temperature and jet-to-target spacing (H/d), sterilization temperature and heat transfer efficiency in water and pineapple juice tests. The Reynolds number was based on the nozzle configuration and liquid flow rate. The study investigated product injection plates formed using two, three or four circular holes (diameter 2 mm), steam injection plates with six, nine or twenty circular holes (diameter 1 mm), steam temperatures of 120, 125 or 130 °C and H/d values of 1, 3, 5 or 7. The different options were tested with water to determine the optimal conditions, and then tested with pineapple juice. The results showed that the optimal conditions from water testing that provided the highest heat transfer efficiency occurred with two jet nozzles, six steam injection plates, a steam temperature of 120 °C and an H/d value of 1.

scholarly journals Effect of shear and magnetic field on the heat-transfer efficiency of convection in rotating spherical shells

2015 ◽  
Vol 204 (2) ◽  
pp. 1120-1133 ◽  
Author(s):  
R.K. Yadav ◽  
T. Gastine ◽  
U.R. Christensen ◽  
L.D.V. Duarte ◽  
A. Reiners
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Transfer Efficiency ◽  
Spherical Shells ◽  
Heat Transfer Efficiency
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