scholarly journals A Resolved Eulerian–Lagrangian Simulation of Fluidization of 1204 Heated Spheres in a Bed With Heat Transfer

2015 ◽  
Vol 138 (4) ◽  
Author(s):  
Zhi-Gang Feng ◽  
Eid S. Alatawi ◽  
Adam Roig ◽  
Cenk Sarikaya
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Fluid Velocity ◽  
Jet Flow ◽  
Uniform Flow ◽  
Temperature Fields ◽  
Lagrangian Simulation ◽  
Simulation And Experiment ◽  
Ib Method

A resolved Eulerian–Lagrangian numerical approach is used to study the heat transfer of 1204 heated spheres fluidized in a slit bed. This approach uses a direct numerical simulation combined with the immersed boundary method (DNS-IB). Pan et al. (2002, “Fluidization of 1204 Spheres: Simulation and Experiment,” J. Fluid Mech., 451, pp. 169–192) studied the fluidization of 1204 spheres by a uniform flow without heat transfer using a fictitious domain-based DNS. The focus of this study is placed on the heat transfer between the heated spheres and fluid and also the fluidization by a jet flow. In the DNS-IB method, fluid velocity and temperature fields are obtained by solving the modified momentum and heat transfer equations, which result from the presence of heated spheres in the fluid. Particles are tracked individually and their velocities and positions are solved based on the equations of linear and angular motions; particle temperature is assumed to be a constant. The momentum and heat exchange between a particle and the surrounding fluid at its surface are resolved using the IB method with the direct forcing scheme. By exploring the rich data generated from the DNS-IB simulations, we are able to obtain statistically averaged fluid and particle velocity as well as particle heat transfer rate in a fluidized bed. Our results on the pressure drop and bed height are compared to the results of Pan et al. (2002, “Fluidization of 1204 Spheres: Simulation and Experiment,” J. Fluid Mech., 451, pp. 169–192), which show good agreements. The case of the fluidization of 1204 spheres by a jet flow has also been studied and compared against the case of the fluidization by a uniform flow. The flow structures, drag, and heat transfer rate of two spheres placed along flow directions have been studied to understand the influence of a neighboring sphere. Results show that the trailing sphere has an insignificant effect on the leading sphere when it comes to the drag and heat transfer rate. On the contrary, the leading sphere can reduce the drag and heat transfer rate of the trailing sphere by more than 20% even when the two spheres are separated by six diameters. This demonstrates the need of a fully resolved DNS in accurately modeling dense particulate flows where a particle could be surrounded by multiple neighboring particles.

Impacts of Newtonian heating, variable fluid properties and Cattaneo–Christov model on MHD stagnation point flow of Walters’ B fluid induced by stretching surface

2020 ◽  
Vol 31 (09) ◽  
pp. 2050125
Author(s):  
Ahmed A. Afify ◽  
Nasser S. Elgazery
Keyword(s):  
Heat Transfer ◽  
Stagnation Point ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Temperature Fields ◽  
Variable Fluid Properties ◽  
Fluid Properties ◽  
Opposite Behavior ◽  
The Mathematical Model ◽  
Walters B Fluid

MHD viscoelastic (Walters’-B) fluid flow close to the stagnation point region along an extending plate with the changeable fluid properties’ influences has been debated. Heat transfer’s features are scrutinized via Cattaneo–Christov (CC) theory. The mathematical model for the physical problem is tackled numerically via Chebyshev pseudospectral (CPS) technique. The existing outcomes are supported by recent research and have acquired a suitable agreement. The numerical outcomes reveal that temperature fields are more pronounced for Fourier’s law case. Further, the opposite behavior is noticed with the heat transfer rate. Higher values of the conjugate parameter result in an increment of the heat transfer rate and temperature field. Fluid flow’s features, as well as physical quantities, are substantially varied via variable fluid properties.

HEAT GENERATION AND ABSORPTION IN MHD FLOW OF CASSON FLUID PAST A STRETCHING WEDGE WITH VISCOUS DISSIPATION AND NEWTONIAN HEATING

2018 ◽  
Vol 80 (3) ◽  
Author(s):  
Imran Ullah ◽  
Sharidan Shafie ◽  
Ilyas Khan
Keyword(s):  
Heat Transfer ◽  
Skin Friction ◽  
Heat Transfer Rate ◽  
Heat Generation ◽  
Transfer Rate ◽  
Fluid Velocity ◽  
Mhd Flow ◽  
Casson Fluid ◽  
Skin Friction Coefficient ◽  
Fluid Temperature

The dissipative flow of Casson fluid in the presence of heat generation and absorption is investigated. The flow is induced due to stretching wedge. The similarity transformations were used to to transformed the governing equations into ordinary differential equations. The transformed equations are solved numerically via Keller-box method. Numerical results for skin friction coefficient are compared and found in excellent agreement with published results. The effects of pertinent parameters on velocity and temperature profiles as well as skin friction and heat transfer rate are graphically displayed and analyzed. It is noticed that fluid velocity drops with the increase of Casson fluid and magnetic parameters when the wedge is stretching faster than free stream. It is also noted that the heat transfer rate at wedge surface reduces with the increase of Eckert number, whereas the reverse trend is noted in the case of Casson and radiation parameters. Moreover, with increasing of heat generation or absorption parameter the fluid temperature rises.

scholarly journals Magnetohydrodynamic mixed convection in a nanofluid filled tubular enclosure

2020 ◽  
Vol 4 (1) ◽  
pp. 19-24
Author(s):  
Mohammad Mokaddes Ali
Keyword(s):  
Heat Transfer ◽  
Mixed Convection ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Temperature Fields ◽  
Convection Flow ◽  
Governing Equations ◽  
Convection Regime ◽  
Special Cases ◽  
Flow Domain

Mixed convection flow in a tubular enclosure filled with nanofluid in the presence of a magnetic field is numerically investigated in the present study. The bottom and top curved wall of the enclosure are respectively kept isothermally hot and cool while the remaining walls are insulated. The governing equations are formulated based on Boussinesq assumptions and solved with finite element method. The computation is carried out for mixed convection regime (0.1 ≤ Ri ≤ 10) and also natural convection regime (10 < Ri ≤ 100) with fixed values of remaining parameters. A detailed parametric discussion is presented for the physical properties of flow and temperature distributions in terms of streamlines, isotherms, average heat transfer rate within the flow domain. The results show that the flow and temperature fields affected by varying of pertinent parameters. Moreover, heat transfer rate is increased by 139.50% with the increase in Richardson number from 0.1 to 100. The increasing rate of heat transfer due to Ri is respectively decreased by 58.11% with varying of Ha from 0 to 60 and increased by 23.97% with the addition of nanoparticles up to 3%. Comparison is performed against the previously published results on the basis of special cases and found to be in excellent agreement.

MIXED CONVECTIVE SLIP FLOWS IN A VERTICAL PARALLEL PLATE MICROCHANNEL WITH SYMMETRIC AND ASYMMETRIC WALL HEAT FLUXES

2012 ◽  
Vol 36 (3) ◽  
pp. 207-218 ◽  
Author(s):  
Hamid Niazmand ◽  
Behnam Rahimi
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Friction Coefficient ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Parallel Plate ◽  
Flux Ratio ◽  
Heat Fluxes ◽  
Temperature Fields ◽  
Slip Flows

Mixed convective gaseous slip flows in an open-ended vertical parallel-plate channel with symmetric and asymmetric wall heat fluxes are numerically investigated. Buoyancy effects on developing and fully developed solutions are studied using the SIMPLE algorithm. The velocity and temperature fields are examined for different values of Knudsen number, mixed convection parameter and heat flux ratio. It is found that increasing Gr/Re leads to an increase in the heat transfer rate and friction coefficient. Also, rarefaction effects decrease the heat transfer rate and friction coefficient. The friction coefficient decreases with an increase in heat flux ratio.

scholarly journals Study of the Influence of the Lack of Contact in Plate and Fin and Tube Heat Exchanger on Heat Transfer Efficiency under Periodic Flow Conditions

Energies ◽  
2021 ◽  
Vol 14 (13) ◽  
pp. 3779
Author(s):  
Marcin Łęcki ◽  
Dariusz Andrzejewski ◽  
Artur N. Gutkowski ◽  
Grzegorz Górecki
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Air Gap ◽  
Temperature Fields ◽  
Periodic Flow ◽  
Flow Conditions ◽  
Tube Heat Exchanger ◽  
Fin Tube

Plate fin-tube heat exchangers are widely used in air conditioning and refrigeration systems and other industry fields. Various errors made in the manufacturing process can result in the formation of an air gap between the tube and fin. Several numerical simulations were carried out for a symmetric section of plate fin-tube heat exchanger to study the influence of air gap on heat transfer under periodic flow conditions. Different locations and sizes of an air gap spanning 1/2 circumference of the tube were considered for the range of airflow velocities. Velocity and temperature fields for cases with air gap were compared with ideal thermal contact cases. Blocking of heat flow by the gap leads to the reduction of heat transfer rate. Fin discontinuity in the front of the tube causes the smallest reduction of the heat transfer rate in comparison to the ideal tube-fin contact, especially for thin slits. The rear gap position is the worst in the smallest gap range. Therefore, reversing the flow direction can lead to up to a 15% heat transfer increase, if mainly the rear gaps are present. The introduction of a thin slit in the front of the tube leads to convective heat transfer enhancement, which should be further investigated.

scholarly journals Control temperature fluctuations in two-phase CuO-water nanofluid by transfiguration of the enclosures

2020 ◽  
pp. 334-334
Author(s):  
Hadi Pourziaei Araban ◽  
Javad Alinejad ◽  
Ganji Domiri
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Natural Convection ◽  
Heat Transfer Rate ◽  
Wall Temperature ◽  
Transfer Rate ◽  
Volume Fraction ◽  
Temperature Fields ◽  
Two Phase ◽  
Flux Boundary Condition

The innovation of this paper is to simulate two-phase nanofluid natural convection inside the transformable enclosure to control the heat transfer rate under different heat flux. Heat transfer of a two-phase CuO-water nanofluid in an enclosure under different heat flux has many industrial applications including energy storage systems, thermal control of electronic devices and cooling of radioactive waste containers. The Lattice Boltzmann Method based on the D2Q9 method has been utilized for modeling velocity and temperature fields. Streamlines, isotherms and nanoparticle volume fraction, have been investigated for control the heat transfer rate for several cases. The purpose of this feasibility study is to achieve uniform temperature profiles and Tmax < 50?C under different heat flux. Natural convection heat transfer in the rectangular and parallelogram enclosures with positive and negative angular adiabatic walls were simulated. The average wall temperature under heat flux boundary condition has been studied to predict optimal levels of effective factors to control the maximum wall temperature. The results illustrated parallelogram enclosures with positive angle of case 1 and case 3 and 4 with rectangular enclosures were best cases for considering physical conditions. Average of temperature for these cases were 37.9, 29.7 and 38.2, respectively.

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