1,721,180 research outputs found
An integrated "Reservoir-Plant" strategy for a sustainable and efficient use of geothermal resources
No full textA multidisciplinary approach for the design of geothermal power plants for water dominant resources is here proposed. The importance of a strategic approach is underlined, considering all the connections between the analysis of the geothermal potential of the reservoir (geophysical exploration and geochemical analysis) with the design of the plant based on thermodynamic and energy considerations, mainly regarding ORC (Organic Rankine Cycles) power plants.This multidisciplinary approach is fundamental for the objective of a sustainable exploitation of medium to low enthalpy sources. The aim of this study is to propose the optimization and management of the global system " reservoir-power plant" as the task of geothermal projects.This approach can be pursued only in a multidisciplinary perspective in which both Engineering and Geological aspects are involved. Numerical simulation appears to be an essential interacting step. After analyzing the problems caused by an incorrect characterization of geothermal source, reinjection temperature and strategy, a method for the numerical simulation of geothermal reservoirs long-term behavior/capacity is discussed. This could be the key instrument to synthesize the strategy inputs. A numerical modeling is performed, using as reference data the history matching of a well known and completely analyzed geothermal field
High-Frequency Treatment of a MixedBoundary Value Problem for the StratifiedAcoustic Half-Space with Increasing WaveSpeed Function
No full textOn geometrically nonlinear mechanics of nanocomposite beams
No full textNowadays, nanocomposite beams undergoing large displacements are effectively employed as basic structural components of small-scale electro-mechanical systems, such as nanoscopic actuators, switches and storage devices, whose design requires accurate assessment of size effects. Thus, in the framework of nonlocal continuum mechanics, the present paper provides a consistent methodology of integral elasticity to address applicative problems of nanocomposite beams undergoing large configuration changes. Constitutive properties of nanofillers are preliminarily evaluated through a novel approach inspired by Homogenization Theory and
then experimentally validated by matching outcomes of Molecular Dynamics. The structural problem of a nanocomposite cantilever undergoing large displacements is formulated exploiting the well-posed stress-driven nonlocal theory to account for scale phenomena. An iterative procedure is put into operation to solve geometrically nonlinear beam problems of current interest in Engineering Science. Effects of mass fractions and distribution patterns of nanofillers on size-dependent structural responses are numerically investigated and discussed
Numerical simulation of geothermal resources: a critical overlook
No full textThe numerical simulation is a challenging part of the study of the geothermal resources. In this paper some of the main problems, criticalities and issues related to both simulation of reservoirs and ground thermal analysis are treated. Numerical simulation is successfully applied in several scientific fields and to solve a great number of engineering problems. Several applications in geothermal energy are possible, like reservoir engineering, ground heat exchange for HVAC (Heating, Ventilation and Air Conditioning) applications, environmental impact, hydrogeology.
An interdisciplinary approach is necessary to pursue an aware and reliable utilization of the numerical models, due to the great complexity of the geothermal phenomenon. The different backgrounds involved are Numerical Analysis, Earth Sciences, Energy Engineering, Geochemistry. In this paper the authors discuss about the numerical simulation of the resource (generally considered): large spatial scale (reservoir engineering) and small spatial scale (shallow systems)
examples are both illustrated. Particular attention is paid on these aspects: thermophysical parameters, boundary conditions, physical equations of the model, potential assessment, coupling of the “plant-reservoir” system. All of them are important to elaborate a critical and engineering point of view. For example, physical hypothesis and assumptions about the system are two of the main criticalities in the application of numerical approach; they have to be clear and reliable and their consequences should be known before the simulation is set up. The principle “trash in, trash out” should be known since the accuracy level of the input data is not always dealt as a problem, but it has a great influence on the results. The industry and market operators sometimes look at numerical models in a wrong way. Models should be related to the decisions about the utilization plant (heat/power) size. If the sustainability of a utilization project is seen from a global point of view, in which Environment, Economy, Technology are merged, the
numerical models can be seen as the synthetic instrument to elaborate industrial strategies in relation to the resource durability. A discussion about when and why numerical models should be successfully implemented is carried on, also taking into account case studies and practical examples
L’ipocicloide tricuspide: il duplice approccio di Luigi Cremona ed Eugenio Beltrami
No full textL’ipocicloide tricuspide è uno dei tanti esempi di problemi elementari che hanno attirato grandi matematici, sia che essi abbiano voluto esaminarli approfonditamente, o studiarli soltanto come “amatori”. Tale attrattiva è principalmente motivata da ragioni estetiche, interpretando tale termine da un punto di vista matematico, ovvero la straordinaria capacità di “vedere” con gli occhi della mente le numerose correlazioni, tutt’altro che intuitive, tra fatti, teorie e metodi che suscitano un senso di armonia in chi è in grado di comprenderli, le suggestive “riposte armonie” di Enriques. In questo intervento metteremo in luce, attraverso l’esame dettagliato di un lavoro di Luigi Cremona del 1864 e di due articoli di Eugenio Beltrami, pubblicati nel 1862 e nel 1874, come il senso dell’estetica matematica sia decisamente presente in matematici di tale calibro. Sia Cremona che Beltrami, pur nella diversità di metodo, hanno una visione comune sul far discendere lo studio di un particolare problema elementare (in questo caso l’ipocicloide tricuspide) da principi generali della matematica più avanzata: la teoria delle cubiche, nel caso di Cremona, le trasformazioni quadratiche per quanto riguarda Beltrami. I risultati non differiscono se non per la generalità: Beltrami infatti procede dallo studio generale delle quartiche di terza classe allo specifico dell’ipocicloide, invece Cremona studia direttamente il caso particolare per sottolineare come sia possibile passare a quello generale mediante un’omografia. Tale distinzione di impostazione è strettamente legata alla differenza tra i metodi, sintetico ed analitico, usati dai due, diversità che si evidenzia in modo efficace attraverso la corrispondenza CremonaBeltrami dell’archivio dell’Istituto Mazziniano di Genova. L’analisi dell’ipocicloide tricuspide si situa inoltre come momento di riflessione di Cremona sulla tematica trattata nelle sue opere maggiori del periodo bolognese: lo studio generale delle curve algebriche e quello delle trasformazioni birazionali. Dunque crediamo che, lungi dall’essere limitato ad un problema elementare, lo studio sull’ipocicloide fa da banco di prova per la potenza dei nuovi metodi. Inedito, ma significativo, appare il ruolo giocato da Beltrami in queste riflessioni di Cremona, ruolo che la succitata corrispondenza prova ampiamente. Un’altra caratteristica che risulta evidente dal taglio dato a questi lavori è l’intima compenetrazione che entrambi ritengono debba esserci tra la matematica superiore e la cosiddetta matematica elementare, cosa che si ripeterà più volte nella loro carriera. Ci sembra che valga la pena sottolineare l’interesse dei due autori, nel pieno della loro maturità scientifica, per una tale problematica apparentemente elementare, ma suggestiva per i molteplici e inaspettati contatti con questioni assai diverse, cosa questa che rappresenta il segno distintivo della “bellezza Matematica
On the use of heat pipe principle for the exploitation of medium-low temperature geothermal resources
No full textIn the direct use of geothermal energy without fluid extraction, heat transfer takes place with no alteration of the natural hydrogeological balance of the basin. An interesting solution both for thermal energy and power production could be the application of heat pipe principle, in particular the Closed Loop Two Phase Thermosyphons (CLTPT). In shallow or not much deep geothermal reservoirs with temperature below 100 C, the two phase closed loop thermosyphon can transfer heat very efficiently. In this case the most important task is the enhancement of the heat transfer mechanism between the heat exchanger and the aquifer. In the first part of the paper a review of particular applications connected to the geothermal heat pipe applications is proposed, then an analysis of the main technical elements regarding the geothermal aquifer exploitation through two phase thermosyphon systems are given. Some guidelines for power systems sizing are discussed and a proposal for the design of a single borehole heat extraction system with binary cycle utilization is provided
The Genesis of the Italian School of Algebraic Geometry Through the Correspondence Between Luigi Cremona and Some of His Students
No full textLuigi Cremona is considered the founder of the Italian school of algebraic geometry. He formed a group of students of great value, very active in scientific research. Examining the letters from Eugenio Bertini, Ettore Caporali, and Riccardo De Paolis to Cremona preserved in the archive of the Istituto Mazziniano in Genoa, we have reconstructed their biographies, careers, studies, and relationships with their teacher. They had the merit of cultivating the scientific innovations of the period and passing them on to the subsequent generations
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