Numerical Study on Mixed Convection in Porous Media in a Channel With an Open Cavity Below

2010 ◽  
Author(s):  
Bernardo Buonomo ◽  
Oronzio Manca ◽  
Paolo Mesolella ◽  
Sergio Nardini
Keyword(s):  
Mixed Convection ◽  
Numerical Study ◽  
Fluid Dynamic ◽  
Vertical Wall ◽  
Open Cavity ◽  
Temperature Fields ◽  
Forced Flow ◽  
Heated Wall ◽  
Local Thermal Equilibrium ◽  
Uniform Heat Flux

A numerical analysis of mixed convection in gas saturated metal foam in a horizontal channel with an open cavity heated at uniform heat flux on a vertical wall is studied numerically. Non-local thermal equilibrium and Brinkman-Forchheimer-extended Darcy model are assumed. Boussinesq approximation with constant thermophysical proprieties are considered. Results are carried out for an aluminium foam with 10 PPI and ε = 0.909, the fluid is air and for the assisting case. Results, for different Peclet and Rayleigh numbers, are given in terms of solid and fluid wall temperatures and local Nusselt numbers and stream function and temperature fields. Results show that diffusive effect determined lower temperature values inside the solid and the fluid temperatures are higher in all considered cases. The interaction between the forced flow in the channel and the buoyancy due to the heated wall determines different thermal and fluid dynamic behaviors.

Experimental Analysis of Opposing Flow in Mixed Convection in a Channel With an Open Cavity Below

2005 ◽  
Author(s):  
Oronzio Manca ◽  
Sergio Nardini ◽  
Kambiz Vafai
Keyword(s):  
Reynolds Number ◽  
Mixed Convection ◽  
Flow Visualization ◽  
Vortex Structure ◽  
Open Cavity ◽  
Forced Flow ◽  
Heated Wall ◽  
Heated Plate ◽  
Thermal Plume ◽  
Recirculation Flow

In this paper mixed convection in an open cavity with a heated wall bounded by a horizontal unheated plate is investigated experimentally. The cavity has the heated wall on the opposite side of the forced inflow. The results are reported in terms of wall temperature profiles of the heated wall and flow visualization for Reynolds number (Re) from 100 to 2000 and Richardson number (Ri) in the range 4.3–6400; the ratio between the length and the height of cavity (L/D) is in the range 0.5–2.0 and the ratio between the channel and cavity height (H/D) is equal to 1.0. The present results show that at the lowest investigated Reynolds number the surface temperatures are lower than the corresponding surface temperature for Re = 2000, at same the ohmic heat flux. The flow visualization points out that for Re = 1000 there are two nearly distinct fluid motions: a parallel forced flow in the channel and a recirculation flow inside the cavity. For Re = 100 the effect of a stronger buoyancy determines a penetration of thermal plume from the heated plate wall into the upper channel. Moreover, the flow visualization points out that for lower Reynolds numbers the forced motion penetrates inside the cavity and a vortex structure is adjacent to the unheated vertical plate. At higher Reynolds number the vortex structure has a larger extension at same L/D value.

scholarly journals Effect of Inlet and Outlet Locations on Transverse Mixed Convection Inside a Vented Enclosure

1970 ◽  
Vol 36 ◽  
pp. 27-37 ◽  
Author(s):  
Sumon Saha ◽  
Md. Tofiqul Islam ◽  
Mohammad Ali ◽  
Md. Arif Hassan Mamun ◽  
M Quamrul Islam
Keyword(s):  
Heat Transfer ◽  
Finite Element Method ◽  
Reynolds Number ◽  
Finite Element ◽  
Mixed Convection ◽  
Vertical Wall ◽  
Flow Fields ◽  
Temperature Fields ◽  
Heated Wall ◽  
Element Method

Transverse mixed convection is studied numerically in a vented enclosure with constant heat flux from uniformly heated bottom wall. An external airflow enters the enclosure through an opening in one vertical wall and exits from another opening in the opposite wall. The two-dimensional mathematical model includes the system of four partial differential equations of continuity, linear momentum and energy, solved by the finite element method. Flow fields are investigated by numerical simulations for air flowing with a Reynolds number in the range 50 ≤ Re ≤ 1000, for Richardson numbers: 0 ≤ Ri ≤ 10. Four different locations of inlet and outlets are introduced to analyze the effect of heat transfer in terms of velocity and temperature fields within the enclosure. The computational results show that the location of inlet and outlets alters significantly the temperature distribution in the flow fields and the heat transfer across the heated wall of the cavities. Empirical correlation is developed for relations using Nusselt number, Reynolds number and Richardson number, based on the enclosure height.   Keywords: Mixed convection, finite element method, vented enclosure, Richardson number.Journal of Mechanical Engineering Vol.36 Dec. 2006 pp.27-37DOI = 10.3329/jme.v36i0.808

Study on Natural Convection in Horizontal Parallel Plate Channels Heated on Upper Wall and Partially Filled With Metal Foam

2020 ◽  
Author(s):  
Bernardo Buonomo ◽  
Vincenzo Fardella ◽  
Oronzio Manca ◽  
Sergio Nardini ◽  
Salvatore Pragliola
Keyword(s):  
Porous Medium ◽  
Nusselt Number ◽  
Natural Convection ◽  
Rayleigh Number ◽  
Average Nusselt Number ◽  
Metal Foam ◽  
Open Cavity ◽  
Temperature Fields ◽  
Local Thermal Equilibrium ◽  
Uniform Heat Flux

Abstract In this work, a numerical investigation on two-dimensional steady state natural convection in a horizontal channel partially filled with a porous medium and heated at uniform heat flux from above is carried out. The lower plate is adiabatic. The porous medium is modeled using the Brinkman–Forchheimer-extended Darcy model and the local thermal equilibrium (LTE) hypothesis is assumed. The structure of the porous medium is homogenous and isotropic, the thermophysical properties of the air and the porous medium are temperature independent and the fluid flow is laminar and incompressible. The aluminum foam has 10, 20 and 40 pore per inches (PPI) and its porosity ranges from 0.90 and 0.95. Rayleigh number values are examined, from 6.0 × 104 and 1.2 × 107. Results are presented in terms of velocity and temperature fields, temperature and velocity profiles at different significant sections are shown, to obtain a description of the natural convection inside the open-ended cavity. Finally, Average Nusselt number values are evaluated. The horizontal open cavity partially filled with metal foam presents improved heat transfer behavior for higher Rayleigh numbers. The enhancement depends on the porosity and pore density. The average Nusselt number for the partially filled open cavity is the double of the configuration without the foam, clear configuration, for the highest considered Rayleigh number.

Experimental Investigation on Mixed Convection in a Channel With an Open Cavity Below

2003 ◽  
Author(s):  
Oronzio Manca ◽  
Sergio Nardini ◽  
Ruggero Pitzolu ◽  
Kambiz Vafai
Keyword(s):  
Mixed Convection ◽  
Flow Visualization ◽  
Open Cavity ◽  
Forced Flow ◽  
Heated Wall ◽  
Heated Plate ◽  
Thermal Plume ◽  
Recirculation Flow ◽  
Nusselt Numbers ◽  
Flow And Heat Transfer

Mixed convection in an open cavity with a heated wall bounded by a horizontal unheated plate is investigated experimentally. The cavity has the heated wall on the inflow side. Mixed convection fluid flow and heat transfer within the cavity is governed by the buoyancy parameter, Richardson number (Ri), and the Reynolds number (Re). The results are reported in terms of wall temperature profiles of the heated wall and flow visualization for Re = 100 and 1000, Ri in the range 30–110 (for Re = 1000) and 2800–8700 (for Re = 100), the ratio between the length and the height of cavity (L/D) is in the range 0.5–1.5 and the ratio between the channel and cavity heights (H/D) equal to 0.5 and 1.0. The present results show that the maximum dimensional temperature rise values decrease as the Reynolds and the Richardson numbers decrease. The flow visualization points out that for Re = 1000 there are two nearly distinct fluid motions: a parallel forced flow in the channel and a recirculation flow inside the cavity. For Re = 100 the effect of a stronger buoyancy determines a penetration of thermal plume from the heated plate wall into the upper channel. The dimensionless maximum wall temperatures in terms of L/D had values in ± 5% respect to an average function. Nusselt numbers increase when L/D increase in the investigated range of Richardson numbers.

scholarly journals Natural convection air flow in vertical upright-angled triangular cavities under realistic thermal boundary conditions

2016 ◽  
Vol 20 (5) ◽  
pp. 1407-1420 ◽  
Author(s):  
Jaime Sieres ◽  
Antonio Campo ◽  
José Martínez-Súarez
Keyword(s):  
Natural Convection ◽  
Vertical Wall ◽  
Aperture Angle ◽  
Temperature Fields ◽  
Uniform Heat Flux ◽  
Thermal Boundary Conditions ◽  
Nusselt Numbers ◽  
Horizontal Wall ◽  
Rayleigh Numbers

This paper presents an analytical and numerical computation of laminar natural convection in a collection of vertical upright-angled triangular cavities filled with air. The vertical wall is heated with a uniform heat flux; the inclined wall is cooled with a uniform temperature; while the upper horizontal wall is assumed thermally insulated. The defining aperture angle ? is located at the lower vertex between the vertical and inclined walls. The finite element method is implemented to perform the computational analysis of the conservation equations for three aperture angles ? (= 15?, 30? and 45?) and height-based modified Rayleigh numbers ranging from a low Ra = 0 (pure conduction) to a high 109. Numerical results are reported for the velocity and temperature fields as well as the Nusselt numbers at the heated vertical wall. The numerical computations are also focused on the determination of the value of the maximum or critical temperature along the hot vertical wall and its dependence with the modified Rayleigh number and the aperture angle.

A Numerical Study on the Thermal Control of Lithium Batteries by Composite Phase Change Materials and Metal Foams

2021 ◽  
Author(s):  
Bernardo Buonomo ◽  
Oronzio Manca ◽  
Ferdinando Menale ◽  
Francesco Moriello ◽  
Simone Mancin
Keyword(s):  
Control System ◽  
Phase Change ◽  
Metal Foam ◽  
Numerical Study ◽  
Liquid Fraction ◽  
Convective Heat Transfer Coefficient ◽  
Thermal Control ◽  
Temperature Fields ◽  
Local Thermal Equilibrium ◽  
Thermal Control System

Abstract This study attempts to control the temperature peaks due to the operation of the battery itself by examining a two-dimensional model to numerically investigate the thermal control of a lithium battery of a commercial electric car. The battery has the dimensions of 8 cm × 31 cm × 67 cm and its capacity is equal to 232 Ah with 5.3 kWh. Thermal control is achieved by means of an internal layer of copper or aluminum foam and phase change material (paraffin), placed on the top of the battery and the external surfaces are cooled by a convective flow. The governing equations, written assuming the local thermal equilibrium for the metal foam, are solved with the finite volume method using the commercial code Ansys-Fluent. Different cases are simulated for different thicknesses of the thermal control system and external convective heat transfer coefficient. The results are given in terms of temperature fields, liquid fraction, surface temperature profiles as a function of time and temperature distributions along the outer surface of the battery for the different cases. In addition, some comparisons with pure PCM are provided to show the advantages of the composite thermal control system with PCM inside the metal foam.

scholarly journals Numerical Study of Mixed Convection in a Channel Filled with a Porous Medium

2019 ◽  
Vol 9 (2) ◽  
pp. 211 ◽  
Author(s):  
Filiz Ozgen ◽  
Yasin Varol
Keyword(s):  
Heat Transfer ◽  
Porous Medium ◽  
Mixed Convection ◽  
Nuclear Waste ◽  
Numerical Study ◽  
Temperature Fields ◽  
Dimensionless Form ◽  
Geothermal Resources ◽  
Nusselt Numbers ◽  
The Finite Difference Method

The heat transfer of mixed convection in a horizontal channel filled with a porous medium has been studied in this article, given that it plays an extensive role in various technical applications, such as flow of fluid in geothermal resources, formations in chemical industries, the storage of radioactive nuclear waste material, and cooling. Those equations written in a dimensionless form have been solved using the finite difference method for different values of the parameters. The results obtained from the study have been presented through streamlines, isotherms, and both local and average Nusselt numbers. It has been observed that parameters such as the Rayleigh and Peclet numbers have an effect on flow and temperature fields.

scholarly journals Three-dimensional numerical study of mixed convection within a ventilated cavity (Shape ‘ L ‘) crossed by a nanofluid under the effect of a magnetic field

2020 ◽  
Vol 307 ◽  
pp. 01027
Author(s):  
S. KHERROUBI ◽  
K. RAGUI ◽  
N. LABSI ◽  
Y.K. BENKAHLA ◽  
A. BOUTRA
Keyword(s):  
Magnetic Field ◽  
Mixed Convection ◽  
Volume Fraction ◽  
Numerical Study ◽  
Vertical Wall ◽  
Three Dimensional ◽  
Convection Heat Transfer ◽  
Left Wall ◽  
Ventilated Cavity ◽  
The Right

The present work is dedicated to the three-dimensional numerical study of mixed convection heat transfer, taking place within a ventilated cavity (of shape L) crossed by Cu-water nanofluid. The enclosure is subjected to the action of a magnetic field. The ventilation is assured by two openings of the same size. The cold flow enters by an opening practiced at the top of the left wall, and exits by another opening practiced at the bottom of the right vertical wall. All the cavity walls are maintained at the same temperature, superior to that of the entering flow, except the side walls which are considered as adiabatic. The control parameters are: the Reynolds number and the Hartmann number as well as the nanoparticles volume fraction.

Thermo-Fluid Dynamics of an Array of Impinging Ionic Jets in a Crossflow

2010 ◽  
Author(s):  
Walter Grassi ◽  
Daniele Testi
Keyword(s):  
Fluid Dynamic ◽  
Impinging Jets ◽  
Negative Ion ◽  
Forced Flow ◽  
Heated Wall ◽  
Electrical Currents ◽  
Square Duct ◽  
Liquid Crystal Thermography ◽  
Nusselt Numbers ◽  
Bottom Side

Laminar to weakly turbulent mixed convection in a square duct heated from the bottom side is highly strengthened by ionic jets generated by an array of high voltage points, opposite to the heated strip. Negative ion injection is activated within the dielectric liquid HFE-7100. Local temperatures on the heated wall are measured by liquid crystal thermography. Distributions of the Nusselt number are obtained at different forced flow rates, applied heat flows, and transiting electrical currents. In correspondence of the point emitters, higher Nusselt numbers in the impingement areas are measured and an analogy with the thermo-fluid dynamic behavior of an array of submerged impinging jets in a crossflow is drawn. The diameter of the ionic jets is evaluated and an electrohydrodynamic Reynolds number is employed for correlation and similarity purposes.

Natural Convection in a Partitioned Vertical Enclosure Heated With a Uniform Heat Flux

2006 ◽  
Vol 129 (6) ◽  
pp. 717-726 ◽  
Author(s):  
Kamil Kahveci
Keyword(s):  
Heat Flux ◽  
Nusselt Number ◽  
Natural Convection ◽  
Thermal Resistance ◽  
Average Nusselt Number ◽  
Numerical Study ◽  
Finite Thickness ◽  
Vertical Wall ◽  
Uniform Heat Flux ◽  
Uniform Heat

This numerical study looks at laminar natural convection in an enclosure divided by a partition with a finite thickness and conductivity. The enclosure is assumed to be heated using a uniform heat flux on a vertical wall, and cooled to a constant temperature on the opposite wall. The governing equations in the vorticity-stream function formulation are solved by employing a polynomial-based differential quadrature method. The results show that the presence of a vertical partition has a considerable effect on the circulation intensity, and therefore, the heat transfer characteristics across the enclosure. The average Nusselt number decreases with an increase of the distance between the hot wall and the partition. With a decrease in the thermal resistance of the partition, the average Nusselt number shows an increasing trend and a peak point is detected. If the thermal resistance of the partition further declines, the average Nusselt number begins to decrease asymptotically to a constant value. The partition thickness has little effect on the average Nusselt number.

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