Analytical multipoint moment matching reduction of distributed thermal networks

In this paper, the multipoint moment matching method for model order reduction of discretized linear thermal networks is extended to distributed linear thermal networks. As a result, from the analytical canonical forms of distributed linear thermal networks, reduced thermal networks are derived analytically. This direct construction of the reduced network, from the exact analytical solutions, avoids the inevitable inaccuracies inherent in conventional surface and volume meshing. It allows nearly exact reduced thermal network construction by domain decomposition for arbitrarily complicated structures.     

Use of zeolite-rich rocks and waste materials for the production of structural lightweight concretes

This paper aims at testing the use of mixtures constituted by natural zeolitized products and SiC-bearing industrial wastes (sludge deriving from polishing of porcelain stoneware tiles, hereafter DPM) for the production of lightweight expanded aggregates as constituents of structural and/or thermo-insulating lightweight concretes. Two commercial products have been used as zeolite natural source: Cab70 (Yellow facies of Campanian Ignimbrite) and IZclino (Turkish clinoptilolite-rich epiclastite). Different amounts of a calcareous material (Pozzano limestones — hereafter CP) from the Sorrento peninsula (Naples — Italy) were also added to a Cab70–DPM mixture. All raw materials were characterized by means of mineralogical (XRPD) and chemical (XRF) analyses. All the products and mixtures were tested from a technological point of view by means of fusibility and firing tests in order to evaluate the expanding properties. It was evidenced that the expansion of the mixture was deeply depending on the occurrence of SiC in the industrial waste. The addition of CP (10 wt.%) to the mixtures accounts for an even increased expansion, though this is accompanied by a worsening of the mechanical features of the material.These results along with literature data allowed to select 3 mixtures (70% Cab70–30% DPM, 70% IZclino–30% DPM, 60% Cab70–30% DPM–10% CP) and each of them was used for the preparation of 5 l of lightweight aggregates afterward employed for the manufacture of lightweight concretes. It was remarked that natural zeolitized materials mixed with DPM (30 wt.%) can provide lightweight aggregates with densities ranging between 0.8 and 1.0 g/cm³ suitable for the preparation of structural lightweight concretes. The addition to the mixture of CP (10 wt.%) produces less dense aggregates (0.6–0.7 g/cm³) potentially useful for the manufacture of thermo insulating lightweight concretes.     

Optimal Operating Conditions For Lab-Scale Ozonation Reactors

A method for the assessment of the optimal operating conditions for a mechanically stirred gas–liquid reactor is presented. The method exploits both fluid dynamic and chemical information. First, the behavior of the specific stirring power as a function of the stirrer speed allows singling out the dispersion region, in which the most efficient gas–liquid mass transfer is achieved. Inside this region, the analysis of experimental data obtained when considering a chemical system reacting at moderate Hatta numbers (i.e., Ha < about 2) allows determination of the rate constants and the fluid dynamic parameters (i.e., the mass transfer coefficient in the absence of chemical reaction and the characteristic diffusion time).     

The effect of physical aging on long-term properties of poly-ether-ketone (PEEK) and PEEK-based composites

The viscoelastic properties of the amorphous and semicrystalline PEEK and of a PEEK-based composite (APC2) have been analyzed as a function of the aging time and related free volume relaxation, at temperatures close to the glass transition temperature. The effect of thermal treatments (physical aging) on the polymer amorphous phase of the three systems is presented. Creep tests approaching the “zero stress” were performed on samples subjected to different thermal histories. The presence of a second phase, namely crystallites and fibers, determines a loss of the mobility of the polymeric amorphous chains and consequently a decrease of the rate of free volume relaxation.     

Modeling and Simulation of a Hybrid Photovoltaic Module Equipped With a Heat-Recovery System

This paper presents a multiphysics model of a hybrid solar panel equipped with a solar concentrator and a cooling interface with heat-recovery capability. It is shown how the temperature profile along the cells can be predicted as a function of the cooling strategy. From this information, the I-V electrical characteristic of the whole module can be derived. An original compact electrothermal macromodel of the photovoltaic module is employed which allows one to properly incorporate the effect of temperature gradients along the cells. By exploiting this macromodel, accurate and efficient electrothermal simulations of the solar system can be carried out with a conventional electrical simulator, like Spice.     

An acoustic-emission characterization of the failure modes in polymer-composite materials

A new methodology for the analysis of failure modes in composite materials by means of acoustic emission techniques has been developed. A single-carbon-fiber composite based on a polyester matrix, has been used as a simple model. The occurrence of fiber-breakage during tensile loading tests has been observed by a polarized light microscope and concurrently detected by a resonant acoustic probe. The resonant probe has been used as a trigger for the reading of fiber failure events. Single acoustic emission events from a wide-band probe has been recorded for FFT Analysis. The single-fiber specimen, having a unique failure mode, has advantages for the standardization of AE techniques for the quantitative analysis of failures in polymer-composite materials.

The same procedure can be exploited to investigate other failure modes namely, fiber matrix solidus debonding and matrix cracking.     

Correlations between steam saturation, fluid composition and well decline in vapor-dominated reservoirs

A large body of field data from Larderello and other vapor-dominated geothermal reservoirs shows striking temporal correlations between (1) decline of well flow rate, (2) gas/steam ratio, (3) chloride concentration, (4) degree of superheat and (5) vapor fraction. The latter is inferred from concentrations of non-condensible gases in samples of well fluid, using chemical phase equilibrium principles. Observed temporal changes in the vapor fraction can be interpreted in terms of a “multiple source” model, as suggested by D'Amore and Truesdell (1979, Models for steam chemistry at Larderello and The Geysers. Proc. 5th Workshop Geothermal Reserv. Engng, Stamford, California, pp. 283–297). This provides clues to the dynamics of reservoir depletion and to the evaluation of well productivity and longevity.     

Digital transmission performance of carrier channels ondistribution power line networks

The analysis of the transmitting features of wire-to-ground and wire-to-wire carrier channels on power distribution networks is performed both in the frequency- and in the time-domain. A new formulation of the lossy ground return parameters is considered, which applies in a wide frequency-range and in case of poorly conductive soil. The sensitivity of the frequency-spectra and longitudinal profiles of the transmitted voltages to the distribution system configuration, load termination and ground resistivity is investigated. The eye-diagram approach is used in order to ascertain the transmission quality of carrier channels on tree- and mesh-type networks, in case of high capacity digital signals