1,720,980 research outputs found
Energy Management In Water Droplet Evaporation. Analysis of the Process
No full textA theoretical model, describing the process of a water droplet travelling in air during a sprinkler irrigation process, and a whole set of analysis parameters were employed to assess the effect of each parameter on some relevant variables, such as: the droplet travel distance, the droplet time of flight, and the final droplet temperature. The description provided, completed by a few assumptions and implemented numerically by means of a Runge-Kutta fourth order method, led to an actual representation of such very complicate process. The results, represented in graphical form by a number of figures, allowed for a thorough assessment of the mutual parametric interactions and showed which parameters prove to affect more significantly the phenomenon
Analisi dello Scambio termico e di Massa in un Componente Edilizio a Raffrescamento Evaporativo
No full textParametric Analysis on Water Droplet Dynamics and Phase Change
No full textThe present paper deepens the analysis on the dynamics and thermal-fluid-dynamics of a sprinkler nozzle-emitted water droplet traveling in air before reaching the ground. The following analysis variables were considered, as main causes of the phenomenon assessed: initial droplet diameter, initial droplet velocity, initial droplet temperature, variable droplet temperature, air temperature, diffusion coefficient of water in air, air relative humidity, inlet droplet throw inclination, thermal radiation, and wind velocity. These variables proved their effect on the droplet travel distance, the droplet time of flight, and the final droplet temperature. The study was carried out thanks to an analytical-numerical model, recently proposed by the same authors of this paper, equipped with a few assumptions that did not alter the realistic description provided. The results proved the effect of each analysis variable and clarify the picture of a complicate yet extremely important phenomenon
Evaluation of the ground-coupled quasi-stationary heat transfer in buildings by means of an accurate and computationally efficient numerical approach and comparison with the ISO 13370 procedure
No full textScambi termici tra edificio e terreno
No full textVengono illustrati i meccanismi di scambio termico che intervengono nella trasmissione di calore attraverso il pavimento di un ambiente in presenza di terreno. Utilizzando i risultati ottenuti applicando un metodo di calcolo di tipo numerico viene verificata la procedura di calcolo elaborata all'interno del gruppo di lavoro (Wg5) del Cen/Tc89 di cui gli autori della poresente memoria sono i rappresentanti italian
Analisi agli Elementi Finiti della Convezione Naturale in Cavità Inclinate con Generazione Interna di Calore
No full textModelling integrated HVAC and refrigeration systems in a supermarket
No full textDecision makers in the supermarket chains ask with ever increasing strength for a comparison between
different HVAC and refrigeration plant solutions, not only in terms of investment costs, but also of energy
needs. The option of heat recovery from the refrigeration plant in favour of the HVAC system for space
heating is being more and more considered, thus requiring the simulation of a complex system where control
strategies play a crucial role. This topic is of great importance also in the view of the reduction of CO2
emissions, because supermarkets are intensive users of energy.
In this paper the preliminary results of a comprehensive model of the HVAC and refrigeration systems in a
supermarket are presented. This model is developed in the framework of the EU project CommONEnergy,
and is based on the Trnsys platform.
A cascade refrigeration system to supply various display cabinets and walk-in coolers is considered for
refrigeration, while a Water Loop Heat Pump (WLHP) system is considered for HVAC. Heat recovery is
performed by collecting heat from the condensers of the refrigeration systems in favour of the WLHP in the
cold season. The effect of a water reservoir is evaluated, as heat storage device for the water loop. The
capabilities of such a plant scheme are discussed in the view of energy savings for the whole supermarket.
Two locations, representative of as many different European climatic zones, are considered. Optimal values
of the activation temperatures for heat recovery, auxiliary heating system and cooling towers are discusses as
well as the most convenient size of the reservoirs in order to minimize the primary energy consumption
Recupero energetico in un forno ad arco elettrico mediante materiali a cambiamento di fase (PCM)
No full textIl recupero di energia, nei processi industriali ove sia effettivamente attuabile, è un tema che ricopre grande importanza nell’ambito della razionalizzazione del fabbisogno energetico di ogni singolo Paese. I forni ad arco elettrico, utilizzati nelle mini-acciaierie per fondere rottami ferrosi, disperdono una cospicua parte di energia in ingresso, sotto forma di calore contenuto nei fumi. Il problema principale, che si verifica nel recupero energetico di questa rilevante quantità di calore, deriva dalla natura dei fumi: il ciclo fusorio è infatti fortemente incostante e ciò determina dei valori di portata e di temperatura talmente variabili, da pregiudicare l’efficienza di un accoppiamento diretto con uno scambiatore di calore. L’utilizzo di un apparato costituito da materiali a cambiamento di fase (Phase Change Material o PCM) permette al contrario di recuperare una parte notevole di questa energia. Ciò è possibile sfruttando cicli di fusione e di solidificazione di questi materiali che, immagazzinando e cedendo energia, a seconda delle temperature dei fumi, limitano le variazioni delle stesse temperature, rendono in tal modo possibile e conveniente “estrarre” il calore. Le prove svolte confermano questa possibilità, evidenziando altresì elevati valori di potenza termica recuperata
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