Natural Convection From a Porous Cavity With Sublayers of Nonuniform Thickness: A Lumped System Analysis

2009 ◽  
Vol 132 (3) ◽  
Author(s):  
R. L. Marvel ◽  
F. C. Lai
Keyword(s):  
Heat Transfer ◽  
System Analysis ◽  
Numerical Study ◽  
Temperature Fields ◽  
Porous Cavity ◽  
Nonuniform Thickness ◽  
Sublayer Thickness ◽  
Vertical Walls ◽  
Quick Estimate ◽  
Rayleigh Numbers

A numerical study has been performed to further investigate the flow and temperature fields in layered porous cavity. The geometry considered is a two-dimensional square cavity comprising of three or four vertical sublayers with nonuniform thickness and distinct permeability. The cavity is subjected to differential heating from the vertical walls. The results obtained are used to further evaluate the capacity of the lumped-system analysis in the prediction of heat transfer results of layered porous cavities. It has been found that predictions by the lumped-system model are reasonably good for the range of Rayleigh numbers encountered in engineering applications. In addition, the predictions improve when the number of sublayers increases as well as the sublayer thickness becomes more uniform. Thus, it proves that the lumped-system analysis can offer a quick estimate of heat transfer result from a layered porous cavity with reasonable accuracy.

Natural Convection From a Layered Porous Cavity With Non-Uniform Sublayers

2007 ◽  
Author(s):  
R. L. Marvel ◽  
F. C. Lai
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
System Analysis ◽  
Numerical Study ◽  
Temperature Fields ◽  
Square Cavity ◽  
Porous Cavity ◽  
Differential Heating ◽  
Vertical Walls

A numerical study has been performed to further investigate the flow and temperature fields in layered porous cavity. The geometry considered is a square cavity with 3 or 4 non-uniform sublayers and is subjected to differential heating from the vertical walls. The results obtained are used to further evaluate the feasibility of using the lumped-system analysis for heat transfer in layered porous cavities as proposed in the previous study. To this end, the effective permeabilities based on the arithmetic and harmonic averaging schemes are examined for their use in the conjunction with the lumped-system analysis.

Influence of Non Uniform Boundary Conditions on Laminar Free Convection in Wavy Square Cavity With Partial Partitions

Volume 1 ◽  
2004 ◽  
Author(s):  
A. Sabeur-Bendehina ◽  
M. Aounallah ◽  
L. Adjlout ◽  
O. Imine ◽  
B. Imine
Keyword(s):  
Heat Transfer ◽  
Boundary Conditions ◽  
Numerical Study ◽  
Laminar Regime ◽  
Uniform Temperature ◽  
Square Cavity ◽  
Vertical Walls ◽  
The Mean ◽  
Rayleigh Numbers ◽  
Partial Partitions

In the present work, a numerical study of the effect of non uniform boundary conditions on the heat transfer by natural convection in cavities with partial partitions is investigated for the laminar regime. This problem is solved by using the partial differential equations which are the equation of mass, momentum and energy. The tests were performed for different boundary conditions and different Rayleigh numbers while the Prandtl number was kept constant. Four geometrical configurations were considered namely three and five undulations with increasing and decreasing partition length. The results obtained show that the non uniform temperature in the vertical walls affects the flow and the heat transfer. The mean Nusselt number decreases comparing with the heat transfer in the undulated square cavity without partitions for all non uniform boundary conditions tested.

scholarly journals Natural Convection in Undivided and Partially Divided Rectangular Enclosures

1981 ◽  
Vol 103 (4) ◽  
pp. 623-629 ◽  
Author(s):  
M. W. Nansteel ◽  
R. Greif
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Temperature Fields ◽  
Transitional Flow ◽  
Two Dimensional ◽  
Injection Flow ◽  
Stabilizing Effect ◽  
Different Temperatures ◽  
Vertical Walls ◽  
Rayleigh Numbers

Heat transfer by natural convection in a two-dimensional rectangular enclosure fitted with partial vertical divisions is investigated experimentally. The horizontal walls of the enclosure are adiabatic while the vertical walls are maintained at different temperatures. The experiments are carried out with water, Pr ≃ 3.5, for Rayleigh numbers in the range, 2.3 × 1010 ⩽ RaL ⩽ 1.1 × 1011, and an aspect ratio, A = H/L = 1/2. The effect of the partial vertical divisions on the fluid flow and temperature fields is investigated by dye-injection flow visualization and by thermocouple probes, respectively. The effect of the partitions on the heat transfer across the enclosure is also studied and correlations for the Nusselt number as a function of RaL and partition length are generated for both conducting and non-conducting partition materials. Partial divisions are found to have a significant effect on the heat transfer; especially when the divisions are adiabatic. The results also indicate that the partial divisions may have a stabilizing effect on the laminar-transitional flow on the heated vertical walls of the enclosure.

Investigation of heat transfer in irregular porous cavity subjected to various boundary conditions

2019 ◽  
Vol 29 (1) ◽  
pp. 418-447 ◽  
Author(s):  
Irfan Anjum Badruddin
Keyword(s):  
Heat Transfer ◽  
Boundary Conditions ◽  
Outer Boundary ◽  
Governing Equations ◽  
Content Type ◽  
Porous Cavity ◽  
Various Boundary Conditions ◽  
Heating Source ◽  
Transfer Behavior ◽  
Vertical Walls

Purpose The purpose of this paper is to investigate the heat transfer in an arbitrary cavity filled with porous medium. The geometry of the cavity is such that an isothermal heating source is placed centrally at the bottom of the cavity. The height and width of the heating source is varied to analyses its effect on the heat transfer characteristics. The investigation is carried out for three different cases of outer boundary conditions such as two outside vertical walls being maintained at cold temperature To, two vertical and top horizontal surface being heated to. To and the third case with top surface kept at To but other surfaces being adiabatic. Design/methodology/approach Finite element method is used to solve the governing equations. Findings It is observed that the cavity exhibits unique heat transfer behavior as compared to regular cavity. The cases of boundary conditions are found to affect the heat transfer rate in the porous cavity. Originality/value This is original work representing the heat transfer in irregular porous cavity with various boundary conditions. This work is neither being published nor under review in any other journal.

scholarly journals Numerical Simulation of Secondary Flow in Gas Turbine Disc Cavities, Including Conjugate Heat Transfer

1996 ◽  
Author(s):  
Y.-H. Ho ◽  
M. M. Athavale ◽  
J. M. Forry ◽  
R. C. Hendricks ◽  
B. M. Steinetz
Keyword(s):  
Heat Transfer ◽  
Secondary Flow ◽  
Conjugate Heat Transfer ◽  
Gas Flow ◽  
Numerical Study ◽  
Labyrinth Seal ◽  
Temperature Fields ◽  
Heat Transfer Analysis ◽  
Flow Rates ◽  
Turbine Disc

A numerical study of the flow and heat transfer in secondary flow elements of the entire inner portion of the turbine section of the Allison T-56/501D engine is presented. The flow simulation included the interstage cavities, rim seals and associated main path flows, while the energy equation also included the solid parts of the turbine disc, rotor supports, and stator supports. Solutions of the energy equations in these problems usually face the difficulty in specifications of wall thermal boundary conditions. By solving the entire turbine section this difficulty is thus removed, and realistic thermal conditions are realized on all internal walls. The simulation was performed using SCISEAL, an advanced 2D/3D CFD code for predictions of fluid flows and forces in turbomachinery seals and secondary flow elements. The mass flow rates and gas temperatures at various seal locations were compared with the design data from Allison. Computed gas flow rates and temperatures in the rim and labyrinth seal show a fair 10 good comparison with the design calculations. The conjugate heat transfer analysis indicates temperature gradients in the stationary intercavity walls, as well as the rotating turbine discs. The thermal strains in the stationary wall may lead to altered interstage labyrinth seal clearances and affect the disc cavity flows. The temperature, fields in the turbine discs also may lead to distortions that can alter the rim seal clearances. Such details of the flow and temperature fields are important in designs of the turbine sections to account for possible thermal distortions and their effects on the performance. The simulation shows that the present day CFD codes can provide the means to understand the complex flow field and thereby aid the design process.

scholarly journals Effects of Anisotropy on Natural Convection in a Vertical Porous Cavity Filled with a Heat Generation

2020 ◽  
pp. 12-27
Author(s):  
Degan Gerard ◽  
Sokpoli Amavi Ernest ◽  
Akowanou Djidjoho Christian ◽  
Vodounnou Edmond Claude
Keyword(s):  
Heat Transfer ◽  
Porous Medium ◽  
Natural Convection ◽  
Rayleigh Number ◽  
Temperature Fields ◽  
Poisson Equations ◽  
Gravitational Vector ◽  
Side Walls ◽  
Rayleigh Numbers ◽  
Vertical Cavity

This research was devoted to the analytical study of heat transfer by natural convection in a vertical cavity, confining a porous medium, and containing a heat source. The porous medium is hydrodynamically anisotropic in permeability whose axes of permeability tensor are obliquely oriented relative to the gravitational vector and saturated with a Newtonian fluid. The side walls are cooled to the temperature  and the horizontal walls are kept adiabatic. An analytical solution to this problem is found for low Rayleigh numbers by writing the solutions of mathematical model in polynomial form of degree n of the Rayleigh number. Poisson equations obtained are solved by the modified Galerkin method. The results are presented in term of streamlines and isotherms. The distribution of the streamlines and the temperature fields are greatly influenced by the permeability anisotropy parameters and the thermal conductivity. The heat transfer decreases considerably when the Rayleigh number increases.

scholarly journals Thermal behavior of premises equipped with different alveolar structures

2015 ◽  
Vol 19 (3) ◽  
pp. 929-938
Author(s):  
Nour Lajimi ◽  
Noureddine Boukadida
Keyword(s):  
Heat Transfer ◽  
Thermal Behavior ◽  
Air Temperature ◽  
Numerical Study ◽  
Convection Heat Transfer ◽  
Convection Heat ◽  
Point Temperature ◽  
Set Point ◽  
Alveolar Structure ◽  
Vertical Walls

This paper presents a numerical study of local thermal behavior. Vertical walls are equipped with alveolar structure and/or simple glazing in East, South and West frontages. Local temperature is assumed to be variable with time or imposed at set point temperature. Results principally show that the simple glazing number has a sensitive effect on convection heat transfer and interior air temperature. They also show that the diode effect is more sensitive in winter. The effect of alveolar structure and simple glazing on the power heating in case with set point temperature is also brought out.

scholarly journals Effect of Heat Source Position in Fluid Flow, Heat Transfer and Entropy Generation in a Naturally Ventilated Room

Mathematics ◽  
2022 ◽  
Vol 10 (2) ◽  
pp. 178
Author(s):  
Mohammed Alghaseb ◽  
Walid Hassen ◽  
Abdelhakim Mesloub ◽  
Lioua Kolsi
Keyword(s):  
Heat Transfer ◽  
Rayleigh Number ◽  
Heat Source ◽  
Numerical Study ◽  
Temperature Fields ◽  
Left Wall ◽  
Heating Efficiency ◽  
Discrete Heat Source ◽  
Volume Method ◽  
The Impact

In this study, a 3D numerical study of free ventilated room equipped with a discrete heat source was performed using the Finite Volume Method (FVM). To ensure good ventilation, two parallel openings were created in the room. A suction opening was located at the bottom of the left wall and another opening was located at the top of the opposite wall; the heat source was placed at various positions in order to compare the heating efficiency. The effects of Rayleigh number (103 ≤ Ra ≤ 106) for six heater positions was studied. The results focus on the impact of these parameters on the particle trajectories, temperature fields and on the heat transfer inside the room. It was found that the position of the heater has a dramatic effect on the behavior and topography of the flow in the room. When the heat source was placed on the wall with the suction opening, two antagonistic behaviors were recorded: an improvement in heat transfer of about 31.6%, compared to the other positions, and a low Rayleigh number against 22% attenuation for high Ra values was noted.

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.

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