1,721,185 research outputs found
Hydrogen purification forPEM Fuel Cell drive systems. Recent progress and perspectives on the CO-PROX reaction
No full textCarbon monoxide oxidation is one of the simplest catalytic reactions and, as such, has been extensively studied in catalysis research. It is receiving considerable research interest because of its importance in many applications, such as lowering CO emissions from automobiles and industries, including removing CO from hydrogen gas fuel.
Hydrogen is used as a fuel for Polymer Electrolyte Membrane Fuel Cells (PEMFCs) and it can be produced through steam reforming or auto-thermal reforming of alcohols1 and hydrocarbons in combination with the water gas shift reaction. Nevertheless, PEMFC Pt anode catalysts are highly sensitive to the presence of even traces of CO and therefore methodologies have to be developed for decreasing the CO concentration in the hydrogen feed down to ppm levels, with a minimum H2 loss.
Currently, Preferential Oxidation of CO (CO-PROX) is one of the most suitable and cost effective methods of purification of H2 because of its high CO conversion rate at low temperature range, which is preferable for PEMFCs operating conditions, with negligible H2 consumption.
Noble metals, particularly platinum-based catalysts, have shown to be active and selective in the CO-PROX reaction2. However, due to high prices and the scarcity of noble metals, attention has been given mostly to non-noble metal or low noble metal catalysts3-7. Transition metals supported on suitable metal oxides are good substitute catalysts and, among them, copper-ceria based catalysts have attracted special interest due to their low cost and easy availability. Furthermore, they seem to be the best choice because results obtained by these catalysts are comparable and sometimes higher than those obtained by the conventional noble metal ones.
This talk will address some aspects of the structure-reactivity relationship in several copper-ceria based systems for the CO-PROX reaction and recent advancements will be briefly reviewed
Experimental Performance Evaluation of Aerogel Glazing Systems
No full textEnergy savings for heating, air conditioning and illuminating plants could be improved by innovative Transparent Insulation Materials (TIMs), which aim to optimize two opposite requirements: transparency and thermal insulation. Aerogel is one of the most promising materials for use in highly energy-efficient windows: in addition to the low thermal conductivity (down to 0.010 W/(m K) in evacuated conditions), a high solar energy and daylight transmittance is achieved. Eight samples were manufactured, by assembling
several types of glass with monolithic and granular aerogel in the interspace. U-values slightly higher than 1 W/m2 K were obtained for all the samples. The monolithic aerogel introduced a better light transmittance (sv = 0.60) than granular one (sv = 0.27), while U-values were comparable in non-evacuated conditions. With respect to a conventional window (double glazing with a low-e layer), 55% reduction
in heat losses was achieved by monolithic aerogel, with only a 25% reduction in light transmittance; for the granular systems, the reduction was about 25% in heat losses, but 66% in light transmission. In order to evaluate the aerogel employing in buildings, a prototype of an aluminum frame window with granular aerogel in interspace was realized. Thermal and acoustic properties of the prototype were evaluated according to the standards. The thermal transmittance of the innovative glazing system was little
lower than 1 W/(m2 K) and it showed also good acoustic properties: the Rw index was 3 dB higher than the one of a conventional window with air in interspace
Glazing systems with silica aerogel for energy savings in buildings
No full textInnovative glazing systems with silica aerogel in interspace were investigated for energy saving in buildings. Aerogel is a promising transparent insulating material, due to its low thermal conductivity (down to 0.010Wm1 K1), high solar factor, high daylight transmittance and remarkable lightweight. Four samples were constructed with float and low-e glasses and granular or monolithic aerogel in interspace
(14 mm thickness). The main optical characteristics of the samples were measured, in order to estimate the light transmittance sv, the solar factor g and the colour rendering index Ra, in compliance with EN 410/2011. Finally, the thermal transmittance was calculated. The monolithic aerogel glazings showed the best performance with respect to granular systems, both for light transmittance (0.62 between
two 4 mm float glasses) and thermal insulation (0.6Wm2 K1). The solar factor was 0.74. Results showed a very promising behaviour of aerogel windows when compared to the windows normally used in Italy and in EU countries: monolithic aerogel between two 4 mm float glasses gave a 62% reduction in heat losses, with a 17% reduction in light transmittance when compared to a double glazing with a low-e
layer; a high solar factor and colour rendering were also assured
Impact noise reduction: laboratory and field measurements of different materials performances
No full textAn investigation of the impact sound insulation performances of different materials currently used as floor coverings in buildings to reduce impact noise is presented in this paper. The following floor coverings for commercial, industrial and residential buildings were tested at the Acoustics Laboratory of the University of Perugia: carpet covering, PVC, corkboard, corkboard with a PVC layer on top, recycled rubber with a PVC layer on top, cork-wood covering, synthetic rubber, undercarpet with carpet on the top. Measurements to evaluate the performances of the floor coverings were carried out, in compliance with UNI EN ISO 140-8: the sound pressure level reduction, due to the installation of a floor covering, was measured in the reverberating room below a heavyweight standard floor. Results were used to calculate, in compliance with UNI EN ISO 717-2, the impact sound attenuation index, ΔL w, useful for a direct comparison between different kinds of floor coverings. Results show that the tested materials haven't good performances: the ΔL w values range from 14 dB (rubber covering) to 35 dB (carpet with undercarpet), so floating floors must be carefully installed to provide a better impact sound attenuation. Finally, field impact sound insulation measurements of a floor equipped with two different coverings were carried out. Results allowed to verify a calculation model for acoustic performances estimation of buildings materials, in compliance with EN UNI 12354-2. A good agreement between measured and calculated data was found
Evaluation of energy, thermal, and daylighting performance of solar control films for a case study in moderate climate
No full textSolar control films could be a suitable way to reduce cooling energy consumptions and to reduce discomfort conditions in existing glazed buildings, but their performance is often evaluated by numerical analysis only. In this paper, an integrated thermal-energy and lighting characterization of solar control films performance was carried out by full-scale experimental setup and numerical analysis: two similar offices, with and without solar control films, in a multifunctional building in moderate climate were investigated. Solar control films strongly reduced the incoming solar radiation (about 60%), not depending on the external solar radiation. During springtime, window films allowed a reduction of about 2-3 C of the indoor air temperature, during sunny days; they influenced also the globe thermometer temperature: with window coatings, it is almost equal to air temperature, whereas with conventional windows, it is about 2 C higher, especially in the afternoon, due to the contribution of glass surface temperature (which is 10 C higher). Furthermore, the contribution of artificial light increases, especially on cloudy days, because the daily average illuminance level was lowered by about 59%. Finally, preliminary simulations showed that the cooling energy demand decreases of about 29% thanks to solar control films, but at the same time the energy demand for heating increases of about 15%
Traffic Noise Pollution: Spectra Characteristics and Windows Sound Insulation in Laboratory and Field Measurements
No full textThe traffic spectra influence on indoor noise through windows is evaluated with laboratory and field measurements. Different traffic noise spectra were registered and reproduced, simulating the outdoor traffic conditions through different windows. Spectrum adaptation terms for the recorded spectra were different from the ones obtained from the Standards, showing that Normative gives a safe evaluation of the Weighted Sound Insulation Index. In field measurements, the level abatements calculated from the Façade Acoustic Insulation Index corrected with the adaptation terms shows that the ones from the Standard do not give a good approximation, while if the level abatements is calculated using the adaptation terms from the registered spectra, a more reliable approximation is achieved. Furthermore, comparing the level abatements for two windows having both Rw equal to 41 dB, very different values were obtained at different frequencies; therefore to characterize acoustic performances of windows, sound insulation curves are also needed. The correlation between the mean difference between adaptation terms calculated from the standard and the one between abatements obtained with pink noise and the ones obtained with the registered spectra is good, but different for road traffic and trains. In both, the difference diminishes when the difference between the abatements increases
Transparent Insulating Materials for building Energy saving: experimental results and performance evaluation
No full textThe reduction of energy consumption for heating and air conditioning and electric energy saving in illumination plants could be improved by innovative Transparent Insulating Materials (TIMs), which aim to optimize two opposite requirements: transparency and thermal insulation. Aerogel is one of the more promising for use in highly energy-efficient windows: in addition to the low thermal conductivity (0.010 W/(m K) in evacuated conditions), a high solar energy and
daylight transmittance is achieved. Eight samples were manufactured, by assembling several types of glass with monolithic and granular aerogel in the interspace. Measurements of transmission and reflection properties were carried out and the energetic and luminous parameters (light transmittance (τv), solar factor (g) and thermal transmittance (U)) were calculated. U-values slightly higher than 1 W/m2K were obtained for all the samples. The monolithic aerogel introduces a better light transmittance (τv = 0.60) than granular one (τv = 0.27), while U-values are comparable in not evacuated conditions. In order to evaluate the aerogel employing in buildings, a prototype of an aluminium frame window with granular aerogel in interspace was realized. Thermal and acoustic properties of the prototype were evaluated according to the standards. The thermal transmittance of the innovative glazing system was little lower than 1 W/(m2 K) and it showed also good acoustic properties: the Rw index was 3 dB higher than the one of a conventional window with air in interspace
Misure spettrofotometriche per la caratterizzazione delle proprietà ottiche di vetri con pellicole a controllo solare.
No full textTra i materiali innovativi che si sono diffusi negli ultimi anni vi sono le cosiddette pellicole a controllo solare, da applicare a lastre vetrate, con marcate proprietà riflettenti. Il lavoro, effettuato presso il Laboratorio di Termotecnica dell’Università di Perugia, presenta una vasta campagna sperimentale per la determinazione delle proprietà ottiche (trasmissione e riflessione spettrali) di vetri semplici e doppi di vari spessori, con applicazione di pellicole a
controllo solare di diverso tipo. A partire dai dati sperimentali, si sono calcolati i parametri che caratterizzano le prestazioni illuminotecniche ed energetiche del materiale, come il fattore te, sia per l’incidenza normale che per alcuni angoli di incidenza significativi. I dati ottenuti possono essere impiegati in codici di calcolo per la valutazione delle prestazioni energetiche ed illuminotecniche degli edifici
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