scholarly journals Numerical analysis of mixed convection characteristics inside a ventilated cavity including the effects of nanoparticle suspensions

2017 ◽  
Vol 21 (5) ◽  
pp. 2205-2215
Author(s):  
Ehsan Sourtiji ◽  
Mofid Gorji-Bandpy
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Pressure Drop ◽  
Mixed Convection ◽  
Volume Fraction ◽  
Numerical Study ◽  
Solid Volume Fraction ◽  
Maximum Heat ◽  
Outlet Port ◽  
Maximum Heat Transfer

A numerical study of mixed convection flow and heat transfer inside a square cavity with inlet and outlet ports is performed. The position of the inlet port is fixed but the location of the outlet port is varied along the four walls of the cavity to investigate the best position corresponding to maximum heat transfer rate and minimum pressure drop in the cavity. It is seen that the overall Nusselt number and pressure drop coefficient vary drastically depending on the Reynolds and Richardson numbers and the position of the outlet port. As the Richardson number increases, the overall Nusselt number generally rises for all cases investigated. It is deduced that placing the outlet port on the right side of the top wall is the best position that leads to the greatest overall Nusselt number and lower pressure drop coefficient. Finally, the effects of nanoparticles on heat transfer are investigated for the best position of the outlet port. It is found that an enhancement of heat transfer and pressure drop is seen in the presence of nanoparticles and augments with solid volume fraction of the nanofluid. It is also observed that the effects of nanoparticles on heat transfer at low Richardson numbers is more than that of high Richardson numbers. <br><br><font color="red"><b> This article has been retracted. Link to the retraction <u><a href="http://dx.doi.org/10.2298/TSCI190625278E">10.2298/TSCI190625278E</a><u></b></font>

Effect of Periodicity of Non-Uniform Sinusoidal Side Heating on Natural Convection in an Anisotropic Porous-Enclosure

2011 ◽  
Vol 110-116 ◽  
pp. 1613-1618 ◽  
Author(s):  
S. Kapoor ◽  
P. Bera
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Natural Convection ◽  
Stream Function ◽  
Numerical Study ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Maximum Heat ◽  
Maximum Heat Transfer ◽  
Porous Enclosure

A comprehensive numerical study on the natural convection in a hydrodynamically anisotropic as well as isotropic porous enclosure is presented, flow is induced by non uniform sinusoidal heating of the right wall of the enclosure. The principal directions of the permeability tensor has been taken oblique to the gravity vector. The spectral Element method has been adopted to solve numerically the governing differential equations by using the vorticity-stream-function approach. The results are presented in terms of stream function, temperature profile and Nusselt number. The result show that the maximum heat transfer takes place at y = 1.5 when N is odd.. Also, increasing media permeability, by changing K* = 1 to K* = 0.2, increases heat transfer rate at below and above right corner of the enclosure. Furthermore, for the all values of N, profiles of local Nusselt number (Nuy) in isotropic as well as anisotropic media are similar, but for even values of N differ slightly at N = 2.. In particular the present analysis shows that, different periodicity (N) of temperature boundary condition has the significant effect on the flow pattern and consequently on the local heat transfer phenomena.

Numerical Simulation of Oblique Air Jet Impingement on a Heated Flat Plate

2016 ◽  
Vol 9 (1) ◽  
Author(s):  
Abhishek B. Bhagwat ◽  
Arunkumar Sridharan
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Flat Plate ◽  
Numerical Study ◽  
Jet Impingement ◽  
Maximum Heat ◽  
Air Jet ◽  
Maximum Heat Transfer ◽  
Vertical Jet

Jet impingement cooling has been studied extensively as this finds applications in the areas of reactor safety, electronic cooling, etc. Here, the convective heat transfer process between the air jet impingement on a uniformly heated inclined flat plate is studied numerically. In this numerical study, 3D simulations are carried out using commercial CFD code to investigate the effect of angle of inclination of plate, Reynolds number, and distance between the nozzle exit and the plate on the heat transfer characteristics. V2F model has been used to model turbulence for various nozzle–plate distance and Reynolds number. It can be concluded that V2F model predicts the Nusselt number variation on the plate satisfactorily. It is observed that point of maximum heat transfer is at the stagnation point in case of vertical jet impinging on a horizontal plate, while it shifts away from the point of impingement for the case of a vertical jet impinging on an inclined flat surface. The shift is toward the “compression side” or the “uphill side” of the air jet. The results are validated with experimental data from the literature. Detailed analysis of local heat transfer coefficients, velocity contours, temperature contours, and Nusselt number variations on the flat plate is presented.

scholarly journals Numerical Simulation of the Cooling of Heated Electronic Blocks in Horizontal Channel by Mixed Convection of Nanofluids

2020 ◽  
Vol 2020 ◽  
pp. 1-11
Author(s):  
Mustapha Ait Hssain ◽  
Rachid Mir ◽  
Youness El Hammami
Keyword(s):  
Heat Transfer ◽  
Mixed Convection ◽  
Volume Fraction ◽  
Numerical Study ◽  
Solid Volume Fraction ◽  
Simple Algorithm ◽  
Separation Distance ◽  
Horizontal Channel ◽  
Laminar Mixed Convection ◽  
Finite Volume Approach

The present work is devoted to the numerical study of steady and laminar mixed convection of nanofluid (water nanoparticles) in a horizontal channel provided with sources of heat at constant temperature, which simulate hot electronic components. The transport equations for continuity, momentum, and energy are solved with finite volume approach using the SIMPLE algorithm. The effective thermal conductivity and the dynamic viscosity of the nanofluid are calculated using, respectively, the Maxwell-Garnett and Brinkman model. The influence of the volume fraction of the nanoparticles 0%≤φ≤10%, Reynolds numbers 5≤Re≤75, the distance between the blocks 0≤d/H≤3, and the types of nanoparticles added (TiO2, Al2O3, CuO, Ag, Cu, and MgO) were investigated and discussed. It emerges from this simulation that the heat transfer increases with the increase in the volume fraction of the nanoparticles and the Reynolds number and decreases with the augmentation of separation distance between heated sources. Moreover, the study shows that the heat transfer is improved by 20% at a solid volume fraction of 10% of Cu nanoparticles.

scholarly journals Mixed convection in an eccentric annulus filled by copper nanofluid

2016 ◽  
Vol 20 (5) ◽  
pp. 1597-1608 ◽  
Author(s):  
Wael El-Maghlany ◽  
Elazm Abo ◽  
Ali Shahata ◽  
Yehia Eldrainy
Keyword(s):  
Nusselt Number ◽  
Mixed Convection ◽  
Richardson Number ◽  
Average Nusselt Number ◽  
Volume Fraction ◽  
Numerical Study ◽  
Solid Volume Fraction ◽  
Convection Flow ◽  
Numerical Work ◽  
Remarkable Effect

A numerical study of mixed convection flow and heat transfer of Copper (Cu)-water nanofluid inside an eccentric horizontal annulus is presented. The inner and outer cylinders are kept at constant temperatures as Th and Tc, respectively. The inner cylinder rotates to generate the forced convection effect. The numerical work was carried out using an in-house CFD code written in FORTRAN. Different scenarios were explored to explain the effects of different parameters on the studied problem. These parameters are Richardson number, eccentricity ratio, and solid volume fraction. The range of the Richardson number Ri, solid volume fraction of the nanoparticles ?, and the eccentricity ratioe, are 0.01 ? Ri ? 100 (natural convection), 0 ? ? ? 0.05, 0 ? e ? 0.9 respectively. All results were performed with thermal Grashof number Gr, and radius ratio Rr, equaled to 104 and 2, respectively. The effects of eccentricity, nanoparticles volume fraction, and Richardson number on the average Nusselt number, streamlines and isotherms were investigated. Results were discussed, and were found to be in good agreement with previous works. It was also found that, the eccentricity has a positive remarkable effect on the average Nusselt number, while the effect of nanoparticles concentration was more pronounced at mixed convection region (Ri=1).

scholarly journals Numerical study of mixed convection heat transfer in lid-driven cavity utilizing nanofluid: Effect of type and model of nanofluid

2015 ◽  
Vol 19 (5) ◽  
pp. 1575-1590 ◽  
Author(s):  
Nader Pourmahmoud ◽  
Ashkan Ghafouri ◽  
Iraj Mirzaee
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Nusselt Number ◽  
Mixed Convection ◽  
Volume Fraction ◽  
Numerical Study ◽  
Published Data ◽  
Driven Cavity ◽  
Laminar Mixed Convection ◽  
Special Cases

Numerical investigation of the laminar mixed convection in two-dimensional lid driven cavity filled with water-Al2O3, water-Cu or water-TiO2 nanofluids is done in this work. In the present study, the top and bottom horizontal walls are thermally insulated while the vertical walls are kept at constant but different temperatures. The governing equations are given in term of the stream function-vorticity formulation in the non-dimensionalized form and then solved numerically by second-order central difference scheme. The thermal conductivity and effective viscosity of nanofluid have been calculated by Maxwell-Garnett and Brinkman models, respectively. An excellent agreement between the current work and previously published data on the basis of special cases are found. The governing parameters are Rayleigh number 103 ? Ra ? 106 and solid concentration 0 ? ? ?0.2 at constant Reynolds and Prandtl numbers. An increase in mean Nusselt number is found as the volume fraction of nanoparticles increases for the whole range of Rayleigh numbers. In addition, it is found that significant heat transfer enhancement can be obtained by increasing thermal conductivity coefficient of additive particles. At Ra=1.75?105, the Nusselt number increases by about 21% for TiO2-Water, and almost 25% for Al2O3-Water, and finally around 40% for Cu-Water nanofluid. Therefore, the highest values are obtained when using Cu nanoparticles. The result obtained using variable thermal conductivity and variable viscosity models are also compared to the results acquired by the Maxwell-Garnett and the Brinkman model.

scholarly journals Heat Transfer Studies of Arrays of Prolate Particles in Gas-Solid Flows

2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
Romana Basit ◽  
Xinyang Li ◽  
Zheqing Huang ◽  
Qiang Zhou
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Volume Fraction ◽  
Numerical Study ◽  
Solid Volume Fraction ◽  
Convection Heat Transfer ◽  
Immersed Boundary ◽  
Orientation Factor ◽  
Boltzmann Method

Numerical study of forced convection heat transfer from arrays of prolate particles is performed using the second-order Immersed Boundary-Lattice Boltzmann Method (IB-LBM). Prolate particle is studied with aspect ratio of 2.5 with solid volume fraction variation from 0.1 to 0.3. For each solid volume fraction, arrays of prolate particles are generated and simulations have been performed to calculate Nusselt number for four different Hermans orientation factors and various Reynolds numbers. From the simulation results, it has been observed that, for any specific value of Hermans orientation factor, Nusselt number increases with the increase of the Reynolds number and solid volume fraction. More importantly, it is found that the effect of orientations on Nusselt number is significant. Nusselt number correlation is developed for ellipsoidal particles as function of Reynolds number, Prandtl number, solid volume fraction, and orientation factors. This correlation is valid for 0.1 ≤ c ≤ 0.3 and 0 < Re ≤ 100 .

scholarly journals Optimization of heat transfer and pressure drop of the channel flow with baffle

2021 ◽  
Vol 40 (1) ◽  
pp. 286-299
Author(s):  
Behzad Ghobadi ◽  
Farshad Kowsary ◽  
Farzad Veysi
Keyword(s):  
Heat Transfer ◽  
Boundary Condition ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Pressure Drop ◽  
Friction Factor ◽  
Heat Transfer Performance ◽  
Transfer Performance ◽  
Maximum Heat ◽  
Maximum Heat Transfer

Abstract In this article, the numerical analysis has been carried out to optimize heat transfer and pressure drop in the horizontal channel in the presence of a rectangular baffle and constant temperature in two-dimension. For this aim, the governing differential equation has been solved by computational fluid dynamics software. The Reynolds numbers are in the range of 2,000 < Re < 10,000 and the working fluid is water. While the periodic boundary condition has been applied at the inlet, outlet, and the channel wall, axisymmetric boundary condition has been used for channel axis. For modeling and optimizing the turbulence, k–ω SST model and genetic algorithm have been applied, respectively. The results illustrate that adding a rectangular baffle to the channel enhances heat transfer and pressure drop. Hence, the heat transfer performance factor along with maximum heat transfer and minimum pressure drop has been investigated and the effective geometrical parameters have been introduced. As can be seen, there is an inverse relationship between baffle step and both heat transfer and pressure drop so that for p/d equal to 0.5, 1, and 1.25, the percentage of increase in Nusselt number is 141, 124, and 120% comparing to a simple channel and the increase in friction factor is 5.5, 5, and 4.25 times, respectively. The results of modeling confirm the increase in heat transfer performance and friction factor in the baffle with more height. For instance, when the Reynolds number and height are 5,000 and 3 mm, the Nusselt number and friction factor have been increased by 35% and 2.5 times, respectively. However, for baffle with 4 mm height, the increase in the Nusselt number and friction factor is 68% and 5.57 times, respectively. It is also demonstrated that by increasing Reynolds number, the maximum heat transfer performance has been decreased which is proportional to the increase in p/d and h/d. Moreover, the maximum heat transfer performance in 2,000 Reynolds number is 1.5 proportional to p/d of 0.61 and h/d of 0.36, while for 10,000 Reynolds number, its value is 1.19 in high p/d of 0.93 and h/d of 0.15. The approaches of the present study can be used for optimizing heat transfer performance where geometrical dimensions are not accessible or the rectangular baffle has been applied for heat transfer enhancement.

Buoyancy Driven Heat Transfer of Nanofluids in a Tilted Enclosure

2010 ◽  
Vol 132 (6) ◽  
Author(s):  
Kamil Kahveci
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Rate ◽  
Inclination Angle ◽  
Transfer Rate ◽  
Volume Fraction ◽  
Solid Volume Fraction ◽  
Particle Radius ◽  
Maximum Heat ◽  
Average Heat ◽  
Maximum Heat Transfer

Buoyancy driven heat transfer of water-based nanofluids in a differentially heated, tilted enclosure is investigated in this study. The governing equations (obtained with the Boussinesq approximation) are solved using the polynomial differential quadrature method for an inclination angle ranging from 0 deg to 90 deg, two different ratios of the nanolayer thickness to the original particle radius (0.02 and 0.1), a solid volume fraction ranging from 0% to 20%, and a Rayleigh number varying from 104 to 106. Five types of nanoparticles, Cu, Ag, CuO, Al2O3, and TiO2 are taken into consideration. The results show that the average heat transfer rate from highest to lowest is for Ag, Cu, CuO, Al2O3, and TiO2. The results also show that for the particle radius generally used in practice (β=0.1 or β=0.02), the average heat transfer rate increases to 44% for Ra=104, to 53% for Ra=105, and to 54% for Ra=106 if the special case of θ=90 deg, which also produces the minimum heat transfer rates, is not taken into consideration. As for θ=90 deg, the heat transfer enhancement reaches 21% for Ra=104, 44% for Ra=105, and 138% for Ra=106. The average heat transfer rate shows an increasing trend with an increasing inclination angle, and a peak value is detected. Beyond the peak point, the foregoing trend reverses and the average heat transfer rate decreases with a further increase in the inclination angle. Maximum heat transfer takes place at θ=45 deg for Ra=104 and at θ=30 deg for Ra=105 and 106.

Mixed Convection From a Cylinder With Low Conductivity Baffles in Cross-Flow

2002 ◽  
Vol 124 (6) ◽  
pp. 1064-1071
Author(s):  
Bassam A/K Abu-Hijleh
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Mixed Convection ◽  
Average Nusselt Number ◽  
Cross Flow ◽  
Maximum Heat ◽  
Buoyancy Parameter ◽  
Maximum Heat Transfer ◽  
Laminar Mixed Convection

The problem of laminar mixed convection from an isothermal cylinder with low conductivity baffles in cross flow was solved numerically. The average Nusselt number was calculated at different combinations of number of baffles, baffle height, Reynolds number, and buoyancy parameter. The reduction in the Nusselt number is as much as 75 percent. When using a small number of baffles at low values of buoyancy parameter, an odd number of baffles reduced the Nusselt number more than an even number of baffles, especially at high values of Reynolds number. This is not the case at high values of buoyancy parameter. There is an optimal baffle height, Reynolds number dependent, for maximum heat transfer reduction beyond which an increase in baffle height does not result in further decrease in heat transfer.

Effect of Nanofluid on Heat Transfer Enhancement for Mixed Convection Flow Over a Corrugated Surface

2020 ◽  
Vol 45 (4) ◽  
pp. 373-383
Author(s):  
Nepal Chandra Roy ◽  
Sadia Siddiqa
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Nusselt Number ◽  
Mixed Convection ◽  
Local Nusselt Number ◽  
Richardson Number ◽  
Thermal Boundary Layer ◽  
Volume Fraction ◽  
Convection Flow ◽  
Mixed Convection Flow

AbstractA mathematical model for mixed convection flow of a nanofluid along a vertical wavy surface has been studied. Numerical results reveal the effects of the volume fraction of nanoparticles, the axial distribution, the Richardson number, and the amplitude/wavelength ratio on the heat transfer of Al2O3-water nanofluid. By increasing the volume fraction of nanoparticles, the local Nusselt number and the thermal boundary layer increases significantly. In case of \mathrm{Ri}=1.0, the inclusion of 2 % and 5 % nanoparticles in the pure fluid augments the local Nusselt number, measured at the axial position 6.0, by 6.6 % and 16.3 % for a flat plate and by 5.9 % and 14.5 %, and 5.4 % and 13.3 % for the wavy surfaces with an amplitude/wavelength ratio of 0.1 and 0.2, respectively. However, when the Richardson number is increased, the local Nusselt number is found to increase but the thermal boundary layer decreases. For small values of the amplitude/wavelength ratio, the two harmonics pattern of the energy field cannot be detected by the local Nusselt number curve, however the isotherms clearly demonstrate this characteristic. The pressure leads to the first harmonic, and the buoyancy, diffusion, and inertia forces produce the second harmonic.

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