1,721,066 research outputs found
Esercitazioni di Termodinamica applicata
No full textIl testo propone per gli allievi dei corsi di Ingegneria Biomedica, Energetica e Meccanica, esercizi di Termodinamica Applicata svolti in modod guidato, con i necessari richiami ai contributi teorici delle lezioni. Per i diversi argomenti trattati sono presentati esempi utili all'applicazione del metodo termodinamico e all'impiego dei modelli fisici sviluppati nella teoria,
Termodinamica applicata e trasmissione del calore per ingegneri
No full textIl testo è strutturato per i fini didattici, rivolto in particolare agli studenti delle lauree in Ingegneria Biomedica, Energetica e Meccanica. A partire dai principi della termodinamica e della trasmissione del calore, in ragione delle regole comportamentali delle sostanze, i contenuti applicativi sono proposti come modelli analitici in grado di simulare la realtà (con accuratezza associata alle ipotesi adottate per formulare il modello), ovvero valutare l'efficienza/inefficienza dei processi, oppure stabilire i limiti fisici di una conversione
Indagine sperimentale sul trasporto radiativo attraverso un materiale isolante a bassa densità
No full textTRANSIENT FREE CONVECTION DEVELOPMENT IN HOT-WIRE EXPERIMENTS
No full textThe transient behavior of free convection along the vertical wire of a hot-wire apparatus has been experimentally investigated at room temperature and ambient pressure, using water and propylene glycol. The development of free convection has been studied using an ad hoc apparatus, in order to obtain the best agreement between the vertical direction and the wire. The measurements were corrected for radiation influences, and the effects induced by free convection were detected at the wire- fluid interface. The convection outcomes have been correlated to fluid properties and test conditions. A suitable time scale has been introduced, which is defined by the modified Fourier and a proper definition of the local Grashof number. The obtained correlation has been applied to data found in the literature. The possibility of describing the free convection development at the wire-fluid interface could enable the fluid properties related to momentum diffusion to be investigated by the hot-wire techniqu
Hot-Wire Method for Kinematic Viscosity Estimation
No full textThis paper explores the characterization of thermal and momentum diffusion properties of condensed phase biological fluids. The widely used transient hot-wire technique for determination of thermal diffusion properties is proposed here to investigate also the apparent kinematic viscosity of fluids with the apparatus commonly adopted for thermal conductivity and/or thermal diffusivity determination. The undesired onset of convection in the determination of thermal diffusion properties is in this case the useful effect measured at the wire-fluid interface. From a theoretical point of view, the onset of convection time at a given vertical position along the wire has been related to the Prandtl number, and the reliability of the kinematic viscosity has been studied and preliminarily tested in the case of wate
Considerazioni sperimentali sull'utilizzo di un sistema a produzione combinata. Confronto con sistemi tradizionali
No full textPubblicazione interna Dipartimento di Energetica Politecnico di Torino, PT DE FT 14
Adapted Laser-Flash Method for Estimating Thermal Diffusion Properties of a Porous Material Surrounded by Compact Layers
Full text linkComposite structures obtained by superimposing layers of different materials
find application in various technological fields. The number of layers and the
characteristics of the constituent materials are chosen based on different needs,
e.g. for thermal protection of metal components or to preserve high mechanical
strength by reducing the overall weight of the structure. For reasons related
to production methods, some layers are not available separately from others
and the study of their thermal properties cannot be achieved using methods
conceived for homogeneous samples. For the evaluation of the properties of
these non-free-standing layers, some modifications of the traditional laser-flash
method are necessary, especially regarding measurements post-processing.
In the present work, the measurements on three-layer samples were carried out
using the classic laser-flash technique, but the analysis of the thermal response
of the sample was carried out with a significantly different approach compared
to that proposed by Parker and for which the method introduced by Cowan
allows heat losses to be considered. The non-normalized thermal response
that is measured on the rear surface of the sample was analyzed with a 1D heat
diffusion analytical solution, considering both the heat losses on the front and
rear surfaces of the sample and the finite pulse effect.
The tested samples are three layers of the same material (Ti6Al4V) but with
a different structure. In fact, the two external layers are compact, while the
intermediate one is made up of sintered powder of various porosities, which
is deposited through additive manufacturing. Since the thermal properties of
the internal porous layer are of great interest (in particular its apparent thermal
conductivity), the article describes the procedure adopted to estimate them and
discusses their identifiability. Furthermore, using the thermal conductivity data
available in the literature, a first validation of the adapted laser-flash method is
also provided
Efficiency of cogeneration systems based on high temperature fuel cells coupled with thermoelectric devices
No full textExperimental Investigation on Thermal Conductivity and Thermal Diffusivity of Water-Agar Gel from Room Temperature to –60°C
Full text linkFrom a thermal point of view, water-agar gel can reproduce the behavior of human soft tissues with a good approximation. For this reason, agar gel is widely used to mimic the thermal diffusion inside the latter, in order to study the effect on human tissues of new techniques and probes used to solve various health diseases. Cryoablation is part of these techniques and its effectiveness strongly depends on the biological response of the tissues to the freezing action and heat diffusion and therefore on their thermo-physical properties. This study presents the values of thermal conductivity and thermal diffusivity, measured on water-agar gel samples, using the transient plane source method, forward and backward from room temperature down to −60°C. The freezing transient and the temperature at which the phase transition begins are highlighted, as well as the temperature dependence of both thermal conductivity and diffusivity
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