scholarly journals Fluid Flow and Heat Transfer Analysis of Quadratic Free Convection in a Nanofluid Filled Porous Cavity

2021 ◽  
Vol 39 (3) ◽  
pp. 876-884
Author(s):  
Jino Lawrence ◽  
Vanav Kumar Alagarsamy
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Fluid Flow ◽  
Rayleigh Number ◽  
Convection Heat Transfer ◽  
Darcy Number ◽  
Convection Heat ◽  
Flow And Heat Transfer ◽  
Non Linear ◽  
Convection Parameter

The involvement of non-linear convection effects in a natural convective fluid flow and heat transfer along with the effects of magnetic field in a porous cavity is studied numerically. Cu-water filled cavity of higher temperature at the left wall and lower temperature at the right wall. The governing equations are organized to achieve the required flow by using two-dimensional equations of energy, continuity and momentum. Vorticity-stream function based dimensionless equations are solved using the finite difference techniques. The results are discussed for various dimensionless parameters such as the Darcy number, non-linear convection parameter, Hartmann number, Rayleigh number and solid volume fraction of the nanoparticles. An augment in streamline velocity and convection heat transfer are observed by increasing the Rayleigh number, non-linear convection parameter and Darcy number. The non-linear convection parameter has a lesser effect on the lower Rayleigh numbers. Diminished streamline intensity and reduction in convection heat transfer are noted for an increase in the strength of the applied magnetic field irrespective of the non-linear convection parameter.

Nanofluid Treatment in Existence of Magnetic Field Using Non-Darcy Model for Porous Media

2018 ◽  
pp. 456-555
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Finite Element Method ◽  
Porous Media ◽  
Control Volume ◽  
Convection Heat Transfer ◽  
Darcy Number ◽  
Convection Heat ◽  
Darcy Model ◽  
Flow And Heat Transfer

In this chapter, the non-Darcy model is employed for porous media filled with nanofluid. Both natural and forced convection heat transfer can be analyzed with this model. The governing equations in forms of vorticity stream function are derived and then they are solved via control volume-based finite element method (CVFEM). The effect of Darcy number on nanofluid flow and heat transfer is examined.

Numerical Investigation of Mixed Convection Heat Transfer in Steady Flow Past a Row of Three Square Cylinders

2018 ◽  
Vol 389 ◽  
pp. 164-175
Author(s):  
Houssem Laidoudi ◽  
Bilal Blissag ◽  
Mohamed Bouzit
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Mixed Convection ◽  
Convection Heat Transfer ◽  
Convection Heat ◽  
Thermal Buoyancy ◽  
Flow And Heat Transfer ◽  
Square Cylinders ◽  
Laminar Mixed Convection ◽  
Mixed Convection Heat Transfer

In this paper, the numerical simulations of laminar mixed convection heat transfer from row of three isothermal square cylinders placed in side-by-side arrangement are carried out to understand the behavior of fluid flow around those cylinders under gradual effect of thermal buoyancy and its effect on the evacuation of heat energy. The numerical results are presented and discussed for the range of these conditions: Re = 10 to 40, Ri = 0 to 2 at fixed value of Prandtl number of Pr = 1 and at fixed geometrical configuration. In order to analyze the effect of thermal buoyancy on fluid flow and heat transfer characteristics the main results are illustrated in terms of streamline and isotherm contours. The total drag coefficient as well as average Nusselt number of each cylinder are also computed to determine exactly the effect of buoyancy strength on hydrodynamic force and heat transfer evacuation of each cylinder.

Influence of Flow Acceleration on Convection Heat Transfer of CO2 at Supercritical Pressures and Air in a Vertical Micro Tube

2010 ◽  
Author(s):  
Pei-Xue Jiang ◽  
Rui-Na Xu ◽  
Zhi-Hui Li ◽  
Chen-Ru Zhao
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Wall Temperature ◽  
Convection Heat Transfer ◽  
Heat Fluxes ◽  
Working Fluid ◽  
Convection Heat ◽  
Downward Flow ◽  
Flow Acceleration ◽  
Flow And Heat Transfer

The convection heat transfer of CO2 at supercritical pressures in a 0.0992 mm diameter vertical tube at relatively high Reynolds numbers (Rein = 6500), various heat fluxes and flow directions are investigated experimentally and numerically. The effects of buoyancy and flow acceleration resulting from the dramatic property variations are studied. The Results show that the local wall temperature varied non-linearly for both upward and downward flow when the heat flux was high. The difference in the local wall temperature between upward and downward flow is very small when the other test conditions are held the same, which indicates that for supercritical CO2 flowing in a micro tube as employed in this study, the buoyancy effect on the convection heat transfer is insignificant and the flow acceleration induced by the axial density variation with temperature is the main factor leading to the abnormal local wall temperature distribution at high heat fluxes. The predicted temperatures using the LB low Reynolds number turbulence model correspond well with the measured data. To further study the influence of flow acceleration on the convection heat transfer, air is also used as the working fluid to numerically investigate the fluid flow and heat transfer in the vertical micro tube. The results show that the effect of compressibility on the fluid flow and heat transfer of air in the vertical micro tube is significant but that the influence of thermal flow acceleration on convection heat transfer of air in a vertical micro tube is insignificant.

scholarly journals Numerical study of natural melt convection in cylindrical cavity with hot walls and cold bottom sink

2013 ◽  
Vol 17 (3) ◽  
pp. 853-864 ◽  
Author(s):  
Abdennacer Ahmanache ◽  
Noureddine Zeraibi
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Heat Exchanger ◽  
Rayleigh Number ◽  
Aspect Ratio ◽  
Cylindrical Cavity ◽  
Numerical Study ◽  
Convection Heat Transfer ◽  
Bulk Temperature ◽  
Flow And Heat Transfer

Numerical study of natural convection heat transfer and fluid flow in cylindrical cavity with hot walls and cold sink is conducted. Calculations are performed in terms of the cavity aspect ratio, the heat exchanger length and the thermo physical properties expressed via the Prandtl number and the Rayleigh number. Results are presented in the form of isotherms, streamlines, average Nusselt number and average bulk temperature for a range of Rayleigh number up to 106. It is observed that Rayleigh number and heat exchanger length influences fluid flow and heat transfer, whereas the cavity aspect ratio has no significant effects.

scholarly journals Numerical Investigation of the Effect of Baffle Inclination Angle on Nanofluid Natural Convection Heat Transfer in A Square Enclosure

2019 ◽  
Vol 12 (2) ◽  
pp. 61-71 ◽  
Author(s):  
Barik AL-Muhjaa ◽  
Khaled Al-Farhany
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Nusselt Number ◽  
Fluid Flow ◽  
Natural Convection ◽  
Rayleigh Number ◽  
Average Nusselt Number ◽  
Solid Wall ◽  
Convection Heat Transfer ◽  
Convection Heat

The characteristics of the conjugate natural convection of (Al2O3-water) nanofluid inside differentially heated enclosure is numerically analyzed using COMSOL Multiphysics (5.3a). The enclosure consists of two vertical walls, the left wall has a thickness and maintain at a uniform hot temperature, while the opposite wall at cold temperature and the horizontal walls are isolated. A high thermal conductivity thin baffle has been added on the insulated bottom wall at a different inclination angles. The effect of the volume fractions of nanoparticles (f), Rayleigh number (Ra), solid wall thermal conductivity ratio (Kr), baffle incline angles (Ø) and the thickness of solid wall (D) on the isothermal lines, fluid flow patterns and the average Nusselt number (Nu)  has been investigated. At low Rayleigh number (Ra=103 to 104) the Isothermal lines are parallel with the vertical wall which is characteristic of conduction heat transfer. on the other hand, when Rayleigh number increase to (Ra=106),  the isotherms lines distribution in the inner fluid become parallel curves with the adiabatic horizontal walls of the enclosure and smooth in this case convection heat transfer becomes dominant. As the Rayleigh number further increases, the average Nusselt number enhance because of buoyancy force become stronger. In addition, the fluid flow within the space is affected by the presence of a fin attached to the lower wall that causes blockage and obstruction of flow near the hot wall, hence the recirculation cores become weak and effect on the buoyant force. The maximum value of the stream function can be noticed in case of nanofluid at (Ø=60), whereas they decrease when (Ø > 60), where the baffle obstruction causing decreases in flow movement. So that the left region temperature increases which cause reduction of the convective heat transfer by the inner fluid temperatures. This is an indication of enhancing of insulation. When the inclination angle increases (Ø >90), the baffle obstruction on flow and fluid resistance becomes smaller and the buoyancy strength increase, as a result, the heat transfer is increasing in this case. As a result of increasing the thermal conductivity from 1 to 10, an increase in the amount of heat transferred through the solid wall to the internal fluid have been noticed. This change can be seen in the isothermal lines, also, there was growth and an increase in the temperature gradient. The increasing of wall thickness from (D=0.1 to 0.4) leads to reduce the intensive heating through the solid wall as well as small heat transferred to the inner fluid. Therefore, it can be noticed that when the wall thickness increases the stream function decrease.

Natural Convection and Entropy Generation in a Cavity Filled With Two Horizontal Layers of Nanofluid and Porous Medium in Presence of a Magnetic Field

2015 ◽  
Author(s):  
Ali Al-Zamily ◽  
M. Ruhul Amin
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Heat Flux ◽  
Nusselt Number ◽  
Fluid Flow ◽  
Rayleigh Number ◽  
Entropy Generation ◽  
Darcy Number ◽  
Bejan Number ◽  
Flow Heat

A numerical analysis is performed to study the fluid flow, heat transfer and entropy generation inside a square cavity embedded with heat flux and subject to the horizontal magnetic field. The cavity is consist of two same width layers: first layer filled with nanofluid (Al2O3+water) and second one is saturated porous media filled with a same nanofluid. The uniform constant heat flux is applied partly at the base wall, and the other parts of the base wall are assumed adiabatic. The upper horizontal wall kept adiabatic, while the vertical walls are maintained at constant cold temperature. Finite element method based on the variational formulation is employed to solve the main equations. The results of the present study are based on visualization of heat flow via isotherms and heatfunctions (heatlines), fluid flow via streamfunctions, and irreversibility via Bejan number. Comparisons with previously numerical and experimental published works are performed and the results are found to be in a good agreement. In this study, the effect of the main pertinent parameters, such as: nanoparticles volume fraction (0≤Φ≤0.15), Rayleigh number (104≤Ra≤107), Darcy number (10−1≤Da≤10−5), Hartmann number (0≤Ha≤60) on the fluid flow, heat transfer and entropy generation are investigated. The results show that the effect of the Hartmann on Nusselt number increases as Darcy number increases especially at high Rayleigh number. Also, at Ra=107 and Φ=0.15, the percentage decreasing in Nusselt number due to present magnetic field (Ha=40) are 85.89% at Da=10−1, 87.12% at Da=10−3 and 98.69% at Da=10−5.

scholarly journals Free Convection Heat Transfer from Horizontal Cylinders

Energies ◽  
2021 ◽  
Vol 14 (3) ◽  
pp. 559
Author(s):  
Janusz T. Cieśliński ◽  
Slawomir Smolen ◽  
Dorota Sawicka
Keyword(s):  
Heat Transfer ◽  
Rayleigh Number ◽  
Free Convection ◽  
Convection Heat Transfer ◽  
Horizontal Tube ◽  
Correlation Equations ◽  
Convection Heat ◽  
Number Range ◽  
Heated Cylinder ◽  
Free Convection Heat

The results of experimental investigation of free convection heat transfer in a rectangular container are presented. The ability of the commonly accepted correlation equations to reproduce present experimental data was tested as well. It was assumed that the examined geometry fulfils the requirement of no-interaction between heated cylinder and bounded surfaces. In order to check this assumption recently published correlation equations that jointly describe the dependence of the average Nusselt number on Rayleigh number and confinement ratios were examined. As a heat source served electrically heated horizontal tube immersed in an ambient fluid. Experiments were performed with pure ethylene glycol (EG), distilled water (W), and a mixture of EG and water at 50%/50% by volume. A set of empirical correlation equations for the prediction of Nu numbers for Rayleigh number range 3.6 × 104 < Ra < 9.2 × 105 or 3.6 × 105 < Raq < 14.8 × 106 and Pr number range 4.5 ≤ Pr ≤ 160 has been developed. The proposed correlation equations are based on two characteristic lengths, i.e., cylinder diameter and boundary layer length.

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