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2004 | Buch

Porous and Complex Flow Structures in Modern Technologies

verfasst von: Adrian Bejan, Ibrahim Dincer, Sylvie Lorente, Antonio F. Miguel, A. Heitor Reis

Verlag: Springer New York

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Über dieses Buch

Porous and Complex Flow Structures in Modern Technologies represents a new approach to the field, considering the fundamentals of porous media in terms of the key roles played by these materials in modern technology. Intended as a text for advanced undergraduates and as a reference for practicing engineers, the book uses the physics of flows in porous materials to tie together a wide variety of important issues from such fields as biomedical engineering, energy conversion, civil engineering, electronics, chemical engineering, and environmental engineering. Thus, for example, flows of water and oil through porous ground play a central role in energy exploration and recovery (oil wells, geothermal fluids), energy conversion (effluents from refineries and power plants), and environmental engineering (leachates from waste repositories).

Similarly, the demands of miniaturization in electronics and in biomedical applications are driving research into the flow of heat and fluids through small-scale porous media (heat exchangers, filters, gas exchangers). Filters, catalytic converters, the drying of stored grains, and a myriad of other applications involve flows through porous media.

By providing a unified theoretical framework that includes not only the traditional homogeneous and isotropic media but also models in which the assumptions of representative elemental volumes or global thermal equilibrium fail, the book provides practicing engineers the tools they need to analyze complex situations that arise in practice. This volume includes examples, solved problems and an extensive glossary of symbols.

Inhaltsverzeichnis

Frontmatter
1. Porous Media Fundamentals
Abstract
A porous medium consists of a solid structure with void spaces that are in general complicated and distributed throughout the structure. The void spaces can be interconnected or not. The pores are identifiable regions that serve as elements for the void space. The traditional view of porous media was inspired by porous structures found in nature, for example, packed sand saturated with water that seeps through the pores. Natural porous structures have random features, such as irregular pore shapes and sizes, and irregular connections between the pores. Today we are seeing a growing number of technologies that rely on flows through complex and small-scale passages. The structures formed by such passages can be viewed as designed porous media—structures where the pore shapes, sizes, and connections are special and purposeful, not irregular or random. Designed porous media are components of larger systems and installations that meet global objectives and perform functions under constraints.
Adrian Bejan, Ibrahim Dincer, Sylvie Lorente, Antonio F. Miguel, A. Heitor Reis
2. Flows in Porous Media
Abstract
We now turn our attention to the results that constitute the core of modern research on convective heat and mass transfer through porous media. Our objective is not only to organize the compact presentation of these results, but also to explain their origin. We want to show the student how to anticipate these results and the results for related problems. This is why we begin with methodology. We emphasize the freedom that educators and researchers have in choosing methods to solve problems, present the results, and put results into practice.
Adrian Bejan, Ibrahim Dincer, Sylvie Lorente, Antonio F. Miguel, A. Heitor Reis
3. Energy Engineering
Abstract
The energy crisis of the 1970s and the continuing emphasis on efficiency (the conservation of fuel resources) has led to a complete overhaul of the way in which power systems are analyzed and improved thermodynamically. The new methodology is exergy analysis and its optimization component is known as thermodynamic optimization, or entropy generation minimization (EGM). This new approach is based on the simultaneous application of the first and second laws in analysis and design. In the 1990s it has become the premier method of thermodynamic analysis in engineering education (Moran, 1989; Bejan, 1982, 1996a,b, 1997; Feidt, 1987; Sieniutycz and Salamon, 1990; Kotas, 1995; Moran and Shapiro, 1995; Radcenco, 1994; Shiner, 1996; Bejan et al., 1996) and it is now sweeping every aspect of engineering practice (Stecco and Moran, 1990, 1992; Valero and Tsatsaronis, 1992; Bejan and Mamut, 1999; Bejan et al., 1999). It is particularly well suited for computer-assisted design and optimization (Sciubba and Melli, 1998; Sciubba, 1999a,b).
Adrian Bejan, Ibrahim Dincer, Sylvie Lorente, Antonio F. Miguel, A. Heitor Reis
4. Environmental and Civil Engineering
Abstract
Realistic models of energy systems demand the treatment of installations and their flowing surroundings together, more so when the installations are large and their spheres of impact greater. The interface between energy systems and the environment is formed by flows, environmental flows. In the opening sections of this chapter we review the fundamentals of some of the most important types of flows that govern the behavior of environmental fluids (air, water) and fluid-saturated porous media.
Adrian Bejan, Ibrahim Dincer, Sylvie Lorente, Antonio F. Miguel, A. Heitor Reis
5. Compact Heat Transfer Flow Structures
Abstract
In this chapter we discuss a series of developments that point in the direction of applying porous media concepts to the description, simulation, and optimization of compact systems with complex flow structures. Compact and miniaturized heat exchangers are primary examples of this trend. Other examples are chemical reactors, fiber filters, brush seals, and the modeling of microsegregation during the solidification of alloys. The new aspect highlighted by these developments is that flow structures are optimized so that flow systems exhibit maximum global performance subject to global constraints. Optimization of flow structure means that in the beginning the flow geometry is free to change. The system is free to morph. Global performance is achieved through the generation of flow architecture (Bejan, 2000). The flow structure becomes a porous medium with purpose, that is, a designed porous medium.
Adrian Bejan, Ibrahim Dincer, Sylvie Lorente, Antonio F. Miguel, A. Heitor Reis
6. Living Structures
Abstract
The development of complex cellular systems such as the vertebrates requires the availability of large amounts of oxygen for the metabolic needs of the cells. The respiratory and circulatory systems are the specialized and hierarchically organized flow systems that meet this need. The respiratory system carries oxygen from the air to the pulmonary veins, whereas in the circulatory system oxygen is carried by the blood and is delivered to the cells by the thinnest vessels, the capillaries. A countercurrent of oxygen and carbon dioxide crosses the capillary wall, such that carbon dioxide is extracted from the blood stream and is discharged from the lungs into the atmosphere during exhalation.
Adrian Bejan, Ibrahim Dincer, Sylvie Lorente, Antonio F. Miguel, A. Heitor Reis
7. Drying of Porous Materials
Abstract
Drying is the process of thermally removing volatile substances (e.g., moisture) to yield a solid product. Mechanical methods for separating a liquid from a solid are not considered drying. When a wet solid is subjected to thermal drying, two processes occur simultaneously: transfer of energy (mostly as heat) from the surrounding environment to evaporate the surface moisture, and transfer of internal moisture to the surface of the solid and its subsequent evaporation due to the first process.
Adrian Bejan, Ibrahim Dincer, Sylvie Lorente, Antonio F. Miguel, A. Heitor Reis
8. Multidisciplinary Applications
Abstract
The void spaces of a porous structure can be interconnected or not. In the latter case the void spaces are disconnected “inclusions” that do not allow a flow to permeate through the porous structure. When the inclusions are large, the flow inside each fluid-filled inclusion may play an important role in the global transport of heat and mass through the structure. This is especially true in coarse cavernous structures encountered in building design.
Adrian Bejan, Ibrahim Dincer, Sylvie Lorente, Antonio F. Miguel, A. Heitor Reis
Backmatter
Metadaten
Titel
Porous and Complex Flow Structures in Modern Technologies
verfasst von
Adrian Bejan
Ibrahim Dincer
Sylvie Lorente
Antonio F. Miguel
A. Heitor Reis
Copyright-Jahr
2004
Verlag
Springer New York
Electronic ISBN
978-1-4757-4221-3
Print ISBN
978-1-4419-1900-7
DOI
https://doi.org/10.1007/978-1-4757-4221-3