Book•
Convection in Porous Media
01 Jan 1992-
TL;DR: In this paper, an introduction to convection in porous media assumes the reader is familiar with basic fluid mechanics and heat transfer, going on to cover insulation of buildings, energy storage and recovery, geothermal reservoirs, nuclear waste disposal, chemical reactor engineering and the storage of heat-generating materials like grain and coal.
Abstract: This introduction to convection in porous media assumes the reader is familiar with basic fluid mechanics and heat transfer, going on to cover insulation of buildings, energy storage and recovery, geothermal reservoirs, nuclear waste disposal, chemical reactor engineering and the storage of heat-generating materials like grain and coal. Geophysical applications range from the flow of groundwater around hot intrusions to the stability of snow against avalanches. The book is intended to be used as a reference, a tutorial work or a textbook for graduates.
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TL;DR: In this article, the authors proposed two different approaches for deriving heat transfer correlation of the nanofluid, and investigated the mechanism of heat transfer enhancement of the nano-fluid.
Abstract: The nanofluid is a solid–liquid mixture in which metallic or nonmetallic nanoparticles are suspended. The suspended ultrafine particles change transport properties and heat transfer performance of the nanofluid, which exhibits a great potential in enhancing heat transfer. The mechanism of heat transfer enhancement of the nanofluid is investigated. Based on the assumption that the nanofluid behaves more like a fluid rather than a conventional solid–fluid mixture, this article proposes two different approaches for deriving heat transfer correlation of the nanofluid. The effects of transport properties of the nanofluid and thermal dispersion are included.
2,355 citations
TL;DR: Entropy generation minimization (finite time thermodynamics, or thermodynamic optimization) is the method that combines into simple models the most basic concepts of heat transfer, fluid mechanics, and thermodynamics as mentioned in this paper.
Abstract: Entropy generation minimization (finite time thermodynamics, or thermodynamic optimization) is the method that combines into simple models the most basic concepts of heat transfer, fluid mechanics, and thermodynamics. These simple models are used in the optimization of real (irreversible) devices and processes, subject to finite‐size and finite‐time constraints. The review traces the development and adoption of the method in several sectors of mainstream thermal engineering and science: cryogenics, heat transfer, education, storage systems, solar power plants, nuclear and fossil power plants, and refrigerators. Emphasis is placed on the fundamental and technological importance of the optimization method and its results, the pedagogical merits of the method, and the chronological development of the field.
1,516 citations
TL;DR: In this article, the effective thermal conductivity (ke), permeability (K), and inertial coefficient (f) of high porosity metal foams were derived by considering a circular blob of metal at the intersection of two fibers.
Abstract: In this paper, we present a comprehensive analytical and experimental investigation for the determination of the effective thermal conductivity (ke), permeability (K) and inertial coefficient (f) of high porosity metal foams. In the first part of the study, we provide an analysis for estimating the effective thermal conductivity (ke). Commercially available metal foams form a complex array of interconnected fibers with an irregular lump of metal at the intersection of two fibers. In our theoretical model, we represent this structure by a model consisting of a two-dimensional array of hexagonal cells where the fibers form the sides of the hexagons. The lump is taken into account by considering a circular blob of metal at the intersection. The analysis shows that ke depends strongly on the porosity and the ratio of the cross-sections of the fiber and the intersection. However, it has no systematic dependence on pore density. Experimental data with aluminum and reticulated vitreous carbon (RVC) foams, using air and water as fluid media are used to validate the analytical predictions. The second part of our paper involves the determination of the permeability (K) and inertial coefficient (f) of these high porosity metal foams. Fluid flow experiments were conducted on a number of metal foam samples covering a wide range of porosities and pore densities in our in-house wind tunnel. The results show that K increases with pore diameter and porosity of the medium. The inertial coefficient, f, on the other hand, depends only on porosity. An analytical model is proposed to predict f based on the theory of flow over bluff bodies, and is found to be in excellent agreement with the experimental data. A modified permeability model is also presented in terms of the porosity, pore diameter and tortuosity of our metal foam samples, and is shown to be in reasonable agreement with measured data.
998 citations
TL;DR: In this paper, the authors developed a jump condition based on the non-local form of the volume averaged momentum equation, which produces a jump in the stress but not in the velocity, and this has important consequences for heat transfer processes.
Abstract: The momentum transfer condition that applies at the boundary between a porous medium and a homogeneous fluid is developed as a jump condition based on the non-local form of the volume averaged momentum equation. Outside the boundary region this non-local form reduces to the classic transport equations, i.e. Darcy's law and Stokes' equations. The structure of the theory is comparable to that used to develop jump conditions at phase interfaces, thus experimental measurements are required to determine the coefficient that appears in the jump condition. The development presented in this work differs from previous studies in that the jump condition is constructed to join Darcy's law with the Brinkman correction to Stokos' equations. This approach produces a jump in the stress but not in the velocity, and this has important consequences for heat transfer processes since it allows the convective transport to be continuous at the boundary between a porous medium and a homogeneous fluid.
841 citations
TL;DR: In this article, the Cheng-Minkowycz problem of natural convection past a vertical plate, in a porous medium saturated by a nanofluid, is studied analytically.
Abstract: The Cheng–Minkowycz problem of natural convection past a vertical plate, in a porous medium saturated by a nanofluid, is studied analytically. The model used for the nanofluid incorporates the effects of Brownian motion and thermophoresis. For the porous medium the Darcy model is employed. A similarity solution is presented. This solution depends on a Lewis number Le, a buoyancy-ratio number Nr, a Brownian motion number Nb, and a thermophoresis number Nt. The dependency of the Nusslelt number on these four parameters is investigated.
760 citations