3,226 research outputs found
Luca Giordano, variazioni sul tema e questioni di cronologia. Due nuove versioni di Perseo con Medusa e del Giudizio di Salomone
No full textLa presentazione di due monumentali lavori giovanili di Luca Giordano, un Perseo che decapita Medusa ed un Giudizio di Salomone, e il confronto con le altre interpretazioni dei due temi offerte dal pittore nell’arco della sua carriera, offrono l’occasione di riconsiderare l’evoluzione del linguaggio di Giordano nello snodo cruciale tra il sesto e il settimo decennio del Seicento, dalla maniera neoveneta degli esordi al riberismo adottato sull’onda della “moda tenebrista” che andava in quegli anni affermandosi nei territori della Serenissima.
Attraverso l’esame delle fonti e l’individuazione di alcuni riflessi figurativi dell’inedito Giudizio di Salomone in area veneziana, si avanza l’ipotesi che tale opera sia da identificare con la tela già nella chiesa dei Gesuiti a Venezia
An assessment of the impact of possible CAP reform scenarios on Romanian agriculture
No full textUsing a simplified model, with key-variable the prices of two different possible scenarios of CAP reform after 2013 (moderate and radical), this paper present a comparison between the price effects of implementation of each reform scenario at 2015 horizon on Romanian agriculture. This short analysis shows that, under the presented hypotheses, the net welfare effect, due to the price changes, for the selected products, is positive in both reform scenarios, yet greater in the case of the radical reform. Integrated in the large context of Romanian development, it seems that the influence of CAP reform upon agriculture and rural areas will be most likely a gradual one: an interpenetration between the two scenarios is foreseeable, starting with the moderate reform that will dominate the period around 2013, the reform measures acquiring a more radical character afterwards.CAP reform, Romania, welfare effects, Agricultural and Food Policy,
Valutazione delle prestazioni energetiche ed ambientali di impianti basati su pompe di calore operanti con diversi fluidi refrigeranti
No full textIn questo lavoro sono state valutate attraverso il software TRNSYS le prestazioni energetiche ed ambientali ottenibili da un impianto di tipo idronico, basato su una pompa di calore elettrica ed accoppiato ad un edificio mono-familiare di recente costruzione situato a Padova. In particolare, sono state considerate due tipologie di pompa di calore, una macchina aerotermica ed una geotermica, entrambe operanti con fluidi refrigeranti alternativi: R-410A e R-454B.
Le simulazioni numeriche effettuate hanno confermato come l’utilizzo di una pompa di calore geotermica permetta di incrementare le prestazioni energetiche complessive dell’impianto di circa il 10%, a parità di refrigerante. L’impatto ambientale delle configurazioni impiantistiche studiate è stato valutato per mezzo del TEWI (Total Warming Equivalent Impact). L’utilizzo del refrigerante R-454B comporta da un lato un lieve calo delle prestazioni energetiche complessive dell’impianto, pari al 2-3% su base annuale, mentre consente di ottenere una marcata diminuzione del TEWI. Considerando infatti l’attuale fattore di emissione italiano dell’energia elettrica prelevata da rete, le emissioni totali lungo l’intero ciclo di vita della pompa di calore calano di circa il 25% grazie all’utilizzo del fluido a basso GWP. Tuttavia, seguendo l’attuale trend di riduzione del fattore di emissione ed assumendolo nullo al 2050, tale riduzione può arrivare in prospettiva fino all’80%, azzerando così le emissioni indirette di CO2 dell’impianto
Sizing effects on the energy performance of reversible air-source heat pumps for office buildings
No full textThis paper deals with the numerical analysis of the energy performance of HVAC systems for heating and cooling, based on a reversible electrical air-source heat pump. The aim of this study is to highlight in which way the energy consumption of these systems is influenced by the heat pump modulating capability, the heat pump sizing and the climate. A numerical model based on the bin method and the energy signature procedure, able to take into account the performance of the heat pump at partial load, has been followed in order to calculate the seasonal and annual performance of the HVAC system coupled to a typical office building, located in three different European locations (Frankfurt, Istanbul, Lisbon). Different kinds of heat pumps (mono-compressor on-off, multi-compressor and inverter-driven heat pumps) have been considered. The numerical results presented in this paper point out that the heat pump sizing strongly affects seasonal and annual HVAC energy consumption: the ratio between the full thermal capacity of the heat pump and the building peak load strongly influences the energy performance of the system. It has been demonstrated that, depending on the season, the seasonal performance of the above-mentioned kinds of heat pumps are influenced in a different way by their sizing
Summer Performances of Reversible Air-to-water Heat Pumps with Heat Recovery for Domestic Hot Water Production
No full textAbstractA numerical model for the seasonal performance evaluation of electric air-to-water reversible heat pumps during summer is presented. The model employs the bin-method, as indicated by the standards EN 14825 and UNI/TS 11300-4, but also considers domestic hot water (DHW) production through condensation heat recovery. The model evaluates the heat pump Seasonal Energy Efficiency Ratio (SEER) as function of the heat pump typology (multi-compressor, inverter-driven). The energy saving potential of DHW production integrated with the heat pump cooling function with respect to traditional separate cooling and DHW devices is analyzed as function of the building demand and of the heat pump typology
Climate Influence on Seasonal Performances of Air-to-water Heat Pumps for Heating
No full textAbstractA mathematical model for the evaluation of the seasonal performances of electric air-to-water heat pumps for heating is used to analyze the efficiency of on-off heat pumps, multi-compressor heat pumps and heat pumps with inverter compressor, integrated by electric heaters as back-up system, in the service of several buildings located in different Italian climates.The paper points out the importance of a good dimensioning of the heat pump as a function of the building energy signature and of the climate of the city where the building is placed, in order to enhance the system seasonal efficiency
Annual Performances of Reversible Air Source Heat Pumps for Space Conditioning
No full textAbstractThe paper presents the results obtained by a numerical simulation of a heating and cooling system based on a reversible air-to-water electric heat pump and electric resistances as back-up. According to the procedure suggested by the current standards EN 14825 and UNI/TS 11300-4, by using the bin method the influence of outdoor conditions and of the typology of heat pump installed has been investigated by determining the value assumed by the seasonal coefficient of performance (SCOPon), the seasonal efficiency ratio (SEER) and the annual performance factor (APF). The numerical results allow discussing the rules for an optimal heat pump sizing in a fixed site
Comparison between metallic-foam and finned-tube water-to-air heat exchangers
No full textThe thermal performance of two water-to-air heat exchanger prototypes, with the air-side conventional finned surface replaced by metal foams, is investigated. Two different metal-foam packaging techniques (S-type, K-type) are tested. The heat exchangers are inserted in the same fan-coil case, equipped with a 3-speed fan, to compare their performance under the same operative conditions. A 10 PPI aluminum foam with 96% porosity shows similar pressure drops and air flow rates with respect to the traditional finned fan-coil. Nonetheless, a strong penalty in terms of heat transfer rate is observed with respect to the conventional finned surface, due to the worse tubes-foam thermal contact and to the 60% lower surface-to-volume ratio of the metal-foam. Due to the presence of by-pass corridors for air, the performance of the K-type heat exchanger is worse than that of the S-type. Also the fin efficiency of the metal foam prototypes is lower than that of the traditional heat exchanger. The experimental data highlight that metal foams cannot compete with conventional fins if the tubes-foam thermal contact is not as good as that of finned surfaces
Influence of the hydronic loop configuration on the energy performance of a CO2 heat pump for domestic hot water production in a multi-family building
No full textIn this work, a numerical analysis of the influence of the hydronic loop on the energy performance of a CO2 heat pump dedicated to DHW production for an apartment
block located in Bologna (Italy) is presented. The energy model of the whole heating system, implemented in TRNSYS17, has been validated by means of a monitoring
campaign performed during the winter season of 2017- 2018. The experimental results highlighted a poor and unexpected energy performance of the heat pump. The comparison between experimental and numerical results showed a significant penalty of the heat pump performance due to an erroneous use of the hot stratified
thermal storage system. Outcomes of this paper confirm that CO2 heat pumps are very sensible to the temperature of the fresh water at the inlet of the gas cooler. This value can be strongly reduced thanks to the presence of the stratified tank in the hydronic loop
- …
