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The seasonal energy performance of a cooling system based on an innovative variable-geometry ejector (VGE) is numerically investigated by using TRNSYS. The VGE-based system is mainly driven by solar energy, collected through solar thermal collectors, and is coupled to a residential building located in Porto. A biomass boiler is used as back-up heater. The energy performance of the investigated cooling system is compared with that of a conventional solution, based on a commercial air-to-water chiller. Results point out that, almost 75% of the generator heat demand can be supplied by solar collectors and about 90% of the overall energy input of the ejector-based system is satisfied by renewables. Moreover, numerical simulations confirm how the capability to vary the ejector geometry on the basis of current operating conditions allows to strongly improve the ejector seasonal efficiency. A second series of simulations aimed to further enhance the system performance. A master control logic which extends the VGE operation time in correspondence of favourable ambient conditions was introduced, in order to store additional cooling energy in the cold buffer tank. This strategy has proved to be effective, since the energy consumption of the biomass boiler could be reduced up to 35%.

The thermal performance of latent heat thermal energy storage (LHTES) systems considerably depends on thermal conductivity of adopted phase change materials (PCMs). To increase the low thermal conductivity of these materials, pure PCMs can be loaded with metal foams. In this study, the melting process of pure and metal-foam loaded phase change materials placed in a rectangular shape case is experimentally investigated by imposing a constant heat flux at the top. Two different paraffin waxes with melting point of about 35°C are tested. The results obtained with pure PCM are compared with those achieved from the use of PCM combined with two different porous metals: a 10 PPI aluminum foam with 96% porosity and a 20 PPI copper foam with 95% porosity. The results demonstrate how metal foams lead to a significant improvement of conduction heat transfer reducing significantly the melting time and the temperature difference between the heater and PCM.

Background In recent years, endocrine disrupting compounds (EDCs) have been found in rivers that receive significant inputs of wastewater. Among EDCs, natural and synthetic steroid hormones are recognized for their potential to mimic or interfere with normal hormonal functions (development, growth and reproduction), even at ultratrace levels (ng L−1). Although conjugated hormones are less active than free hormones, they can be cleaved and release the unconjugated estrogens through microbial processes before or during the treatment of wastewater. Due to the need to identify and quantify these compounds, a new fully automated method was developed for the simultaneous determination of the two forms of several steroid hormones (free and conjugated) in different water matrixes and in urine. Results The method is based on online solid phase extraction coupled with liquid chromatography and tandem mass spectrometry (SPE–LC–MS/MS). Several parameters were assessed in order to optimize the efficiency of the method, such as the type and flow rate of the mobile phase, the various SPE columns, chromatography as well as different sources and ionization modes for MS. The method demonstrated good linearity (R2 > 0.993) and precision with a coefficient of variance of less than 10 %. The quantification limits vary from a minimum of 3–15 ng L−1 for an injection volume of 1 and 5 mL, respectively, with the recovery values of the compounds varying from 72 to 117 %. Conclusion The suggested method has been validated and successfully applied for the simultaneous analysis of several steroid hormones in different water matrixes and in urine. Electronic supplementary material The online version of this article (doi:10.1186/s13065-016-0174-z) contains supplementary material, which is available to authorized users.

Sottosistema per il monitoraggio degli sversamenti di idrocarburi in mare con dati satellitari ottici (MODIS e MERIS).

This paper describes the design and development of a C-band Solid State Power Amplifier (SSPA) to be used as TWTA replacement in down-link transmitters.

The problem of the junction of two rectangular waveguides partially filled with dielectric slabs is considered and a comparison with previously obtained results is carried out. A new and more approximate method is suggested and compared with the others.

A MATLAB numerical code to determine the effects of the choice of the balance point and of the thermal storage (puffer) volume on the mean seasonal COP of an on-off electric air-to-water heat pump is presented. The heat pump is used to heat a building and is provided with a puffer and a back-up system (electrical resistances). The code employs as main input parameters: the hourly values of the external air temperature, the heat loss coefficient of the building, the volume and the imposed maximum and minimum temperature of the storage water, the technical data of the heat pump as functions of the source temperatures. The code evaluates the hourly values of the energy lost by the building, of the average temperature of the water in the puffer, of the energy supplied to the building by the heat pump and by the back-up system. By varying the selected values of the balance point and of the storage volume, it is possible to calculate their optimal values in order to maximize the seasonal COP. The results show that a correct choice of the balance point yields a significant increase of the mean seasonal COP of the system, while the effect of the puffer volume is less considerable.

Le antenne integrate attive (AIA), rappresentano la nuova frontiera nella progettazione dei moderni sistemi a radiofrequenza e ad onde millimetriche, sia per applicazioni militari che per applicazioni commerciali. Negli ultimi anni, la progettazione dell’antenna, oltre al raggiungimento dei requisiti sul diagramma di irradiazione, sul guadagno e sull’adattamento di impedenza, richiede una forte integrazione dell’elemento radiante nel sistema. Infatti, nei sistemi di trasmissione, ed in special modo in quelli mobili, è di fondamentale importanza ridurre al minimo la dissipazione di potenza in continua, per aumentare la durata delle batterie e per ridurre il peso e l’ingombro dell’intera unità, riducendo sia le dimensioni dei sistemi di alimentazione che dei sistemi di raffreddamento. Fattori cruciali nelle scelte progettuali saranno quindi l’efficienza, le dimensioni e la larghezza di banda, oltre al controllo delle interferenze elettromagnetiche tra i vari sottosistemi. Allo scopo di investigare questi nuovi concetti e sviluppare strutture innovative, è stato proposto e finanziato il progetto PRIN’05 dal titolo “Antenne Integrate Attive per Terminali Mobili ad Alta Efficienza”. Il progetto di ricerca si pone come obiettivo lo sviluppo di un’antenna integrata attiva per terminali mobili ad alta efficienza per applicazioni in banda Ku. Gli aspetti innovativi proposti riguardano la possibilità di integrazione dell’elettronica di front-end con l’elemento radiante, al fine di migliorare le prestazioni dell’intero trasmettitore. Le problematiche di rilievo sono l’integrazione dello stadio di potenza con il singolo elemento radiante, lo sviluppo di oscillatori VCO basati su1 concetto di injection locking per l’implementazione di array fasati e lo studio delle problematiche di sviluppo di array ad alta efficienza. Per quanto riguarda lo stadio di potenza integrato con l’elemento radiante, l’idea è stata quella di usare quest’ultimo anche come carico armonico per l’ottimizzazione delle prestazioni dello stadio di potenza.

In this contribution an innovative Active Integrate Antenna (AIA) system is presented. Starting from a critical revision of the state-of-the-art, alternative and innovative solutions to obtain a high degree of integration have been considered.

In this work a commercial paraffin PCM (RT35) characterized by a solid-liquid phase change temperature Ts-l = 29 ÷ 36 °C and a low thermal conductivity λ = 0.2 W/m K is experimentally tested submitting it to charging/discharging cycles. The paraffin is contained in a case with a rectangular base and heated from the top thanks to an electrical resistance. The aim of this research is to show the benefits that a 95% porous copper metal foam can bring to a PCM-based system simply loading it, thanks to the consequent strong thermal conductivity increase. The experimental results highlight the positive effects of the copper foam presence such as the heat conduction improvement throughout the system and a significant reduction in time for the complete melting of the PCM. In addition, the experimental data highlight that in the copper-foam-loaded PCM the maximum temperature reached during the heating process is lower than 20 K respect to the test with pure PCM, imposing the same heat flux on the top.