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Über dieses Buch

This Brief describes and analyzes flow and heat transport over a liquid-saturated porous bed. The porous bed is saturated by a liquid layer and heating takes place from a section of the bottom. The effect on flow patterns of heating from the bottom is shown by calculation, and when the heating is sufficiently strong, the flow is affected through the porous and upper liquid layers. Measurements of the heat transfer rate from the heated section confirm calculations. General heat transfer laws are developed for varying porous bed depths for applications to process industry needs, environmental sciences, and materials processing. Addressing a topic of considerable interest to the research community, the brief features an up-to-date literature review of mixed convection energy transport in fluid superposed porous layers.

Inhaltsverzeichnis

Frontmatter

Chapter 1. Introduction

Porous media can be found in many natural systems and engineering applications. Examples include beach sand, human lungs, bread, gravel, soil, and rock, and engineering applications include packed bed reactors, fiberglass insulation, thermal energy storage systems, electronic cooling, crude oil extraction, and nuclear reactors, and the list goes on. For many of these applications, depending on the flow regime, buoyancy effects can play a role in the heat transfer rates, and many of them comprise a porous medium bounded from above by a fluid layer. The general framework of this investigation of mixed convection in fluid-superposed porous layers described in this monograph is established. Prior research addresses natural, forced, and mixed convection in porous layers, and heat transfer correlations have been established based on a blend of experimentation and numerical analysis.
John M. Dixon, Francis A. Kulacki

Chapter 2. Mathematical Formulation and Numerical Methods

Numerical solution of the mass, momentum, and energy conservation equations governing mixed convection in fluid-superposed porous layers is described. The momentum equation includes the Brinkman and Forchheimer terms and the Boussinesq equation of state accounts for buoyancy. The lower boundary of the system is heated over a finite length with the heat sink on the upper surface of the fluid sublayer. Test cases against prior investigations give very good results for free and mixed convection in saturated porous layers and cavities with full bottom heating.
John M. Dixon, Francis A. Kulacki

Chapter 3. Numerical Results

Results of the numerical solution of the mass conservation, DBF, and energy equations are presented. Verification of the solution method is first obtained by reproducing solutions for Rayleigh-Bénard convection, the Horton-Lapwood-Rogers program, and natural convection in fluid-superposed porous layers. For mixed convection in the fluid-superposed porous layer, Nusselt numbers are determined for a wide range of parameter effects: conductivity ratio, thermal dispersion, Prandtl number, Darcy number, and porous layer height ratio. Péclet numbers at which a minimum in the heat transfer coefficient occurs are determined in terms of combinations of these parameters.
John M. Dixon, Francis A. Kulacki

Chapter 4. Measurement of the Heat Transfer Coefficient

The design of the experimental apparatus and the data collection procedure are discussed. The variation of Rayleigh number, Péclet number, Darcy number, dimensionless height ratio, and dimensionless heater length are accounted for in the design of the experimental apparatus. Experimental uncertainty in the measured Nusselt numbers and other dimensionless groups is discussed.
John M. Dixon, Francis A. Kulacki

Chapter 5. Summary of Findings

Mixed convection in a porous layer with a superposed fluid layer heated over a finite length of the lower boundary has been investigated over a large parameter space. The numerical solution uses a one-domain model and avoids the need to explicitly define interface conditions at the fluid-porous sublayer interface. Additional variable porosity terms have been derived to model interfacial effects in the momentum and energy equations. The measurement of overall Nusselt numbers on the heated surface has been conducted for a wide range of Rayleigh number, Péclet number, and porous sublayer height. The numerical results are found to generally fall within the bounds of experimental uncertainty. The following paragraphs summarize the key findings of this investigation.
John M. Dixon, Francis A. Kulacki

Backmatter

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