Nusselt Number and Temperature Distribution in an Horizontal Cavity Containing a Layer of Porous Material at the Bottom

2003 ◽  
Author(s):  
Marcelo J. S. de Lemos ◽  
Viviani T. Magro
Keyword(s):  
Heat Transfer ◽  
Porous Material ◽  
Numerical Solutions ◽  
Control Volume ◽  
Simple Algorithm ◽  
Flow Region ◽  
Porous Matrix ◽  
Layered Porous Media ◽  
Energy Equations ◽  
Volume Method

Horizontally-layered porous media in enclosures represents an important configuration with many technological applications in mechanical and aerospace engineering. This work presents numerical solutions for flow and heat transfer in square cavities partially obstructed with porous material. The microscopic flow and energy equations are integrated in a representative elementary volume in order to obtain a set of equations valid in both the clear flow region and in the porous matrix. A unique set of equations is discretized with the control volume method and solved with SIMPLE algorithm. Heat transfer enhancement across the porous cavity is calculated as the permeability or the porosity of the porous substrate increase.

Turbulent Free Convection in a Composite Enclosure

2003 ◽  
Author(s):  
Marcelo J. S. de Lemos ◽  
Viviani T. Magro
Keyword(s):  
Thermal Field ◽  
Control Volume ◽  
Simple Algorithm ◽  
Flow Region ◽  
Porous Matrix ◽  
Porous Substrate ◽  
Local Flow ◽  
Vertical Walls ◽  
Energy Equations ◽  
Volume Method

This paper deals with the problem of heat transfer in square cavities partially filled with porous material. Local flow and energy equations are integrated in a representative elementary volume in order to obtain a set of equations valid in both the clear flow region and in the porous matrix. A unique set of equations is discretized with the control volume method and solved with the SIMPLE algorithm. Enhancement of convective currents within the porous substrate is detected as the Rayleigh number increases. Thin boundary layers along the cavity vertical walls and stratification of the thermal field are observed for Ra > 109.

Laminar Heat Transfer on a Wall Covered With a Layer of Porous Material Simulated With a Two-Energy Equation Model

2010 ◽  
Author(s):  
Marcelo J. S. de Lemos ◽  
Felipe T. Do´rea
Keyword(s):  
Porous Material ◽  
Control Volume ◽  
Numerical Technique ◽  
Simple Algorithm ◽  
Porous Matrix ◽  
Equation Model ◽  
Energy Model ◽  
Governing Equations ◽  
Volume Method ◽  
Macroscopic Equations

This paper presents simulations for a jet impinging against a flat plane covered with a layer of a porous material. Macroscopic equations for mass, momentum and energy, for the fluid and for the porous matrix, are obtained based on the volume-average concept. The numerical technique employed for discretizing the governing equations was the control volume method with a boundary-fitted non-orthogonal coordinate system. The SIMPLE algorithm was used to handle the pressure-velocity coupling. The effect of porosity and energy model on the local distribution of Nu was analyzed. Results indicate that for low porosity materials, a substantially different Nu number is calculated depending on the energy model applied.

A Thermo-Mechanical Model for a Counterflow Biomass Gasifier

2014 ◽  
Vol 354 ◽  
pp. 227-235
Author(s):  
Marcelo J.S. de Lemos
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Control Volume ◽  
Simple Algorithm ◽  
Thermal Capacity ◽  
Macroscopic Model ◽  
Algebraic Equations ◽  
Medium Permeability ◽  
Mechanical Approach ◽  
Volume Method

This article presents a thermo-mechanical approach to investigate heat transfer between solid and fluid phases in a model gasifier. A two-temperature equation approach is applied in addition to a macroscopic model for laminar flow through a porous moving bed. Transport equations are discretized using the control-volume method and the system of algebraic equations is relaxed via the SIMPLE algorithm. The effects on inter-phase heat transfer due to variation of medium permeability, thermal conductivity and thermal capacity are analyzed. Results indicate that for smaller medium permeabilities, as well as for higher solid-to-fluid thermal capacity and thermal conductivity ratios, enhancement of heat transfer between phases is observed.

scholarly journals Numerical study on characteristics of flow and thermal fields around rotating cylinder

10.30544/450 ◽  
2020 ◽  
Vol 26 (1) ◽  
pp. 71-86
Author(s):  
Kamel Korib ◽  
Mohamed ROUDANE ◽  
Yacine Khelili
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Numerical Study ◽  
Simple Algorithm ◽  
Rotation Rates ◽  
Rotating Circular Cylinder ◽  
Flow And Heat Transfer ◽  
Lift And Drag ◽  
Energy Equations ◽  
Volume Method

In this paper, a numerical simulation has been performed to study the fluid flow and heat transfer around a rotating circular cylinder over low Reynolds numbers. Here, the Reynolds number is 200, and the values of rotation rates (α) are varied within the range of 0 < α < 6. Two-dimensional and unsteady mass continuity, momentum, and energy equations have been discretized using the finite volume method. SIMPLE algorithm has been applied for solving the pressure linked equations. The effect of rotation rates (α) on fluid flow and heat transfer were investigated numerically. Also, time-averaged (lift and drag coefficients and Nusselt number) results were obtained and compared with the literature data. A good agreement was obtained for both the local and averaged values.

Turbulent Impinging Jet Into a Rigid Porous Layer

2011 ◽  
Author(s):  
Marcelo J. S. de Lemos
Keyword(s):  
Porous Layer ◽  
Control Volume ◽  
Numerical Technique ◽  
Simple Algorithm ◽  
Stagnation Region ◽  
Thermally Conducting ◽  
Energy Equations ◽  
Volume Method ◽  
Highly Porous ◽  
Macroscopic Equations

This work shows simulations for a turbulent jet impinging against a flat plane covered with a layer of permeable and thermally conducting material. Distinct energy equations are considered for the porous layer attached to the wall and for the fluid that impinges on it. Parameters such as Reynolds number, porosity, permeability, thickness and thermal conductivity of the porous layer are varied in order to analyze their effects on the local distribution of Nu. The macroscopic equations for mass, momentum and energy are obtained based on volume-average concept. The numerical technique employed for discretizing the governing equations was the control volume method with a boundary-fitted non-orthogonal coordinate system. The SIMPLE algorithm was used to handle the pressure-velocity coupling. Results indicate that inclusion of a porous layer eliminates the peak in Nu at the stagnation region. For highly porous and highly permeable material, simulations indicate that the integral heat flux from the wall is enhanced when a thermally conducting porous material is attached to the wall.

Porous media to intensify natural convection in rectangular enclosures used in building techniques

2020 ◽  
Vol 31 (04) ◽  
pp. 2050061
Author(s):  
A. Baïri ◽  
A. Martín-Garín ◽  
J. A. Millán-García
Keyword(s):  
Heat Transfer ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Numerical Study ◽  
Control Volume ◽  
Vertical Wall ◽  
Simple Algorithm ◽  
Constant Heat Flux ◽  
Physical Parameters ◽  
Volume Method

This numerical study quantifies the natural convective heat transfer occurring in an elongated rectangular cavity whose hot vertical wall generates a constant heat flux while the opposite one is kept isothermal at cold temperature. The study shows that when a layer of porous material is affixed to the hot wall, the aerodynamic phenomena are modified and increase the natural convective transfer. Several configurations were processed, obtained by varying the matrix’s thermal conductivity of the layer, the aspect ratio of the cavity and the Rayleigh number in wide ranges. The numerical solution is obtained by means of the control volume method based on the SIMPLE algorithm. A correlation of the Nusselt–Rayleigh type is proposed, allowing determination of the convective heat transfer for any combination of these physical parameters. It can be applied in various engineering fields including passive heating in building which can be improved by the simple and easy-to-implement assembly version discussed here.

Combined Convection Heat Transfer of Nanofluids Flow over Forward Facing Step in a Channel Having a Blockage

2013 ◽  
Vol 388 ◽  
pp. 185-191 ◽  
Author(s):  
Hussein A. Mohammed ◽  
Mohsen Golieskardi ◽  
K.M. Munisamy ◽  
Mazlan A. Wahid
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Volume Fraction ◽  
Convection Heat Transfer ◽  
Simple Algorithm ◽  
Combined Convection ◽  
Reynolds Number Increase ◽  
Forward Facing Step ◽  
Energy Equations ◽  
Volume Method

Numerical simulations of two dimensional laminar combined convection flows using nanofluids over forward facing step with a blockage are analyzed. The continuity, momentum and energy equations are solved using finite volume method (FVM) and the SIMPLE algorithm scheme is applied to examine the effect of the blockage on the heat transfer characteristics. In this project, several parameters such as different types of nanofluids (Al2O3, SiO2, CuO and ZnO), different volume fraction in the range of 1% - 4%, different nanoparticles diameter in the range of 25nm-80nm were used. Effects of different shapes of blockage (Circular, Square and Triangular) were studied. The numerical results indicated that SiO2nanofluid has the highest Nusselt number. The Nusselt number increased as the volume fraction and Reynolds number increase, while it decreases as the nanoparticles diameter increases. Circular blockage produced higher results compared to triangular and square one.

scholarly journals Turbulence Combined Convective Heat Transfer and Nanofluids Flows over Double Forward Facing Steps

2018 ◽  
Vol 225 ◽  
pp. 01007
Author(s):  
Omar Hussein ◽  
Khairul Habib ◽  
Mohammad Nasif ◽  
Ali Muhsan ◽  
Balaji Bakthavatchalam
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Mixed Convection ◽  
Volume Fraction ◽  
Simple Algorithm ◽  
Numerical Investigations ◽  
Different Types ◽  
Energy Equations ◽  
Volume Method ◽  
Fluid Characteristics

Predictions are reported for mixed convection using various types of nanofluids over forward-facing double steps in a duct. The continuity, momentum and energy equations are discretized and the simple algorithm is applied to link the pressure and flow fields inside the domain. Different types of nanoparticles Al2O3, CuO, SiO2 and ZnO, with different volume fractions in range of 1-4% are investigated to identify their effects on the heat transfer and fluid characteristics. Numerical investigations are conducted using finite volume method. The results indicate that SiO2 -water has the highest Nusselt number followed by Al2O3-water, CuO -water and ZnO-water. The Nusselt number increases as the volume fraction increases but decreases as the nanoparticles diameter increases.

scholarly journals An Unstructured Finite Volume Method for Incompressible Flows With Complex Immersed Boundaries

2009 ◽  
Author(s):  
Lin Sun ◽  
Sanjay R. Mathur ◽  
Jayathi Y. Murthy
Keyword(s):  
Finite Volume Method ◽  
Finite Volume ◽  
Incompressible Flows ◽  
Simple Algorithm ◽  
Flow Region ◽  
Solid Material ◽  
The Body ◽  
Immersed Boundary ◽  
Material Points ◽  
Volume Method

A numerical method is developed for solving the 3D, unsteady, incompressible flows with immersed moving solids of arbitrary geometrical complexity. A co-located (non-staggered) finite volume method is employed to solve the Navier-Stokes governing equations for flow region using arbitrary convex polyhedral meshes. The solid region is represented by a set of material points with known position and velocity. Faces in the flow region located in the immediate vicinity of the solid body are marked as immersed boundary (IB) faces. At every instant in time, the influence of the body on the flow is accounted for by reconstructing implicitly the velocity the IB faces from a stencil of fluid cells and solid material points. Specific numerical issues related to the non-staggered formulation are addressed, including the specification of face mass fluxes, and corrections to the continuity equation to ensure overall mass balance. Incorporation of this immersed boundary technique within the framework of the SIMPLE algorithm is described. Canonical test cases of laminar flow around stationary and moving spheres and cylinders are used to verify the implementation. Mesh convergence tests are carried out. The simulation results are shown to agree well with experiments for the case of micro-cantilevers vibrating in a viscous fluid.

A Numerical and Experimental Investigation of Turbulent Heat Transport Downstream From an Abrupt Pipe Expansion

1983 ◽  
Vol 105 (4) ◽  
pp. 862-869 ◽  
Author(s):  
R. S. Amano ◽  
M. K. Jensen ◽  
P. Goel
Keyword(s):  
Heat Transfer ◽  
Numerical Solutions ◽  
Numerical Study ◽  
Separated Flow ◽  
Flow Region ◽  
Reynolds Numbers ◽  
Turbulent Heat ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Pipe Expansion

An experimental and numerical study is reported on heat transfer in the separated flow region created by an abrupt circular pipe expansion. Heat transfer coefficients were measured along the pipe wall downstream from an expansion for three different expansion ratios of d/D = 0.195, 0.391, and 0.586 for Reynolds numbers ranging from 104 to 1.5 × 105. The results are compared with the numerical solutions obtained with the k ∼ ε turbulence model. In this computation a new finite difference scheme is developed which shows several advantages over the ordinary hybrid scheme. The study also covers the derivation of a new wall function model. Generally good agreement between the measured and the computed results is shown.

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