102,008 research outputs found
The Constructal law: from design in nature to social dynamics and wealth as physics
No full text“The Constructal Law and the Evolution of Design in Nature” offers a new revolutionary
approach based on physics for understanding and predicting the designs that arise in nature, from the oneness of
animate and inanimate designs, the origin of finite-size organs on animals and vehicles, the flow of stresses as the
generator of design in solid structures (skeletons, vegetation), and the global design of human flows. The physics
principle that governs the phenomenon of generation of configuration in nature is the Constructal Law: “For a finitesize
flow system to persist in time (to live), its configuration must change in time such that it provides easier and easier
access to its currents (fluid, energy, species, etc.).
Sistemi torbiditici interagenti nell'avanfossa oligocenica nordappenninica: dati petrografico-stratigrafici del Macigno della Toscana meridionale costiera
No full textNumerical investigation on mixed convection in a non-newtonian fluid inside a vertical duct
No full textSolar Thermal and Biomasses: Renewable Energy for a Sustainable Development
No full textConventional energy sources based on oil, coal and natural gas are damaging economic and social progress, environment and human life. Many people are concerned about these problems and wish to address the symptoms as a matter of urgency, but not all understand the basic causes and consequently do not realize that not only technological, but also social changes are required. It is now widely acknowledged that renewable energy capacity has to be increased by exploiting its enormous potential. Renewable energy education is relatively new field and previously it formed a minor part of the traditional university courses. However, over the past decade, several new approaches have emerged: we see these in the new literature and, even more clearly, in new books. The present treatise, in the authors’ auspices, represent a contribution to this new “incoming science”.
The book is highly recommended to professors, students and professionals in mechanical, civil, environmental, chemical and agricultural engineering. It is also recommended to all the readers interested in the aims, philosophy, structure, design, strategies and overcomes in the use of energy from “solar thermal and biomasses”
7° Congresso Nazionale AIGE
No full textIl 7° Congresso Nazionale dell'Associazione Italiana Gestione Energia si svolge nella Provincia di Cosenza, presso il Centro Congressi dell'Università della Calabria, nel Comune di Rende. La manifestazione si tiene in Calabria per la prima volta
Geometric optimization of X-shaped cavities and pathways according to Bejan’s theory: comparative analysis
No full textThis paper applies Constructal design to study the geometry of a X-shaped isothermal cavity and a X-shaped high conductivity pathway that penetrate into a solid conducting wall. The objective is to minimize the maximal excess of temperature of the whole system, i.e. the hot spots, independent of where they are located. There is uniform heat generation on the solid body, which is insulated on the external perimeter. The total volume and the cavity volume, as well as the high conductivity material volume, are fixed, but the geometric lengths and thickness of both X-shaped configurations can vary. The emerged optimal configurations and performance are reported graphically and numerically. The results indicate that the increase of the complexity of the geometry can facilitate the access of heat currents and improve the thermal performance. The degree of freedom L1/L0 proved to be significant on the performance of the X-shaped isothermal cavity, e.g. the once optimized ratio (L1/L0)o increases approximately 10 % as the area fraction φ increases from φ = 0.05 to 0.3. As for the X-shaped pathway case, it has been demonstrated that the dimensionless thermal conductivity of the path and the area fraction φ have a strong effect on the performance and configuration of the X-shaped blades: the twice minimized θmax,mm decreases approximately 70% as increases from 30 to 300 and it decreases approximately 84% as φ augments from 0.01 to 0.2
Geometric optimization of intruded cavities on the basis of Constructal theory
No full textIn this work the optimization of the shape of open cavities that intrude into a solid conducting wall is considered. The basic
global constraint is that the solid construct must fit into a given volume. The hot spots are located along the solid conducting
wall which generates heat uniformly and it is insulated on the external perimeter, while the cavity represents an heat sink. As
open cavity this region is called ‘‘inverted fin’’ or ‘‘negative fin’’. The aim of this paper is to prove the relation between the
maximization of global performance in terms of heat removal and the morphing architecture of a cavity that intrudes into the
conductive solid. The maximization of the rate of heat transfer in a given volume has led to design new structures for several
engineering applications. In this way, the optimization has been conducted according to the Constructal principle of optimal
distribution of imperfections, in order to achieve as much as possible an optimized flow architecture. Depending on the
particular matter of the cavity that for the present purpose can be convective or isothermal, its optimal shape varies and its
variation can be predicted by the Constructal principle, according to which the optimization of geometry generates a treeshaped
structure with several degrees of freedom. Indeed the system, which is composed by the tree-shaped intruded cavity
into the solid conductive wall, can vary its dimensions in terms of ratios between steams and tributaries. In this work the
tendency by the flows to adopt themselves paths characterized by minimal resistance is demonstrated. In case of isothermal
cavity, the tree-shaped structure tends to reduce the hot spot distributed volumes, as a minimal global thermal resistance is
observed. This trend is registered for the convective cavity as well, but with different results; indeed, when the cavity admits
also a convective heat transfer between internal surfaces and the stream that passes through the cavity, the tree-shaped optimal
geometry changes: the steam now penetrates into the solid body and the tributaries extend themselves completely along his
whole length
Constructal design of X-shaped conductive pathways for cooling a heat-generating body
No full textThis paper applies constructal design to discover the configuration that facilitates the access of the heat
that flows through X-shaped pathways of high-conductivity material embedded within a square-shaped
heat-generating medium of low-conductivity to cooling this finite-size volume. The objective is to minimize
the maximal excess of temperature of the whole system, i.e. the hot spots, independent of where
they are located. The total volume and the volume of the material of high thermal conductivity are fixed,
but the lengths can vary. It was found numerically that the performance of X-shaped pathways is approximately
the same as that the one calculated for a simpler I-shaped blade (i.e. a single pathway of high
thermal conductivity material beginning in the heat sink and ending of such a way that there is spacing
between the tip of the pathway and the insulated wall) for small values of the high thermal conductivity
material and area fraction. However, the X-shaped conductive pathway configuration performs approximately
51% better when compared to I-shaped pathway configuration for larger values of the highconductivity
material and area fraction
Constructal design of non-uniform X-shaped conductive pathways for cooling
No full textThis paper applies constructal design to discover the configuration that facilitates the access of the heat that flows through non-uniform X-shaped pathways of high-conductivity material embedded within a square-shaped heat-generating medium of low-conductivity to cooling this finite-size volume. The objective is to minimize the maximal excess of temperature of the whole system, i.e. the hot spots, independent of where they are located. The total volume and the volume of the material of high thermal conductivity are fixed, but the lengths of the pathways and the angles between the pathways can vary. The configuration was optimized for four degrees of freedom: the two angles between the pathways, and the two ratios between the lengths. It was found numerically that the performance of the non-uniform X-shaped pathways is approximately 10 % better than the performance of the uniform X-shaped pathways, i. e., X-shaped with equal lengths and thicknesses. When compared to the configuration calculated for a simpler I-shaped blade (i.e. a single pathway of high thermal conductivity material beginning in the isothermal wall and ending of such a way that there is spacing between the tip of the pathway and the insulated wall) the non-uniform X-shaped pathways configuration performs 56 % better
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