1,720,979 research outputs found
Cambiamento climatico. Il punto di vista fisico tecnico
No full textIl cambiamento climatico, probabilmente il più importante dei problemi che l’umanità si trova ad affrontare, è causato dalle concentrazioni atmosferiche eccessive di “gas serra” (come anidride carbonica, metano e protossido di azoto per citare i più importanti). Questi gas hanno la poco gradita proprietà di lasciar passare le radiazioni solari in entrata ma di ostacolare le radiazioni infrarosse in uscita dalla Terra. Gli impatti del cambiamento climatico sono ormai tali da condizionare le nostre scelte di base più elementari: come adattare l’abitazione, dove programmare le vacanze, che auto acquistare, in quale industria cercare lavoro, che cibi scegliere e quali consumi abbandonare. In questo quadro, il volume si propone di far risparmiare tempo e fatica a chi, pur non essendo climatologo di professione, vuole ugualmente informarsi in modo serio sul cambiamento climatico. A tal fine, nel testo si sono presentati i punti chiave dei Rapporti del Comitato Intergovernativo sul Cambiamento Climatico (IPCC) e, per completare la panoramica, non si sono trascurate nemmeno le segnalazioni di rischi aggiuntivi provenienti, in “tempo reale”, da fonti molto attendibili (la rivista Nature per prima). Per facilitare la comprensione si è seguito il ben collaudato “format” dei volumi didattici: prima le conoscenze di base, successivamente le metodologie utilizzate ed alla fine la presentazione dei risultati ottenuti. Particolare cura è stata dedicata alle esigenze di render sempre note le fonti delle informazioni utilizzate e, allo stesso tempo, di spiegare e non dare mai scontate le affermazioni chiare solo agli “addetti ai lavori”
Il cambiamento climatico. Il punto di vista fisico-tecnico. Nuova ediz
No full textIl cambiamento climatico è causato dall’aumento della concentrazione atmosferica dei gas serra (come anidride carbonica, metano e protossido di azoto, per citare solo i più importanti). Questi gas lasciano passare le radiazioni solari in entrata ma ostacolano le radiazioni infrarosse in uscita dalla Terra. Le conseguenze del cambiamento climatico sono ormai talmente significative da condizionare il futuro dell’umanità in generale e dei giovani in particolare.
Il volume si rivolge a chi, pur non essendo climatologo di professione, vuole ugualmente informarsi in modo serio sul cambiamento climatico. A tal fine, nel testo sono esaminati i punti chiave dei Rapporti del Comitato Intergovernativo sul Cambiamento Climatico (IPCC) senza tralasciare una presentazione delle conoscenze di base, la disamina delle metodologie utilizzate e la discussione dei risultati ottenuti dalle ricerche.
Di particolare importanza è il quarto capitolo, nel quale viene illustrato il 'Sesto Rapporto IPCC sul cambiamento climatico – Le basi fisiche', pubblicato il 9 agosto 2021, e sono riassunte le conclusioni della COP26, svoltasi a Glasgow dal 31 ottobre al 15 novembre 2021
Verso una nuova energetica. Dalle fonti esauribili alla decarbonizzazione
No full textL’aumento delle ondate di calore, i periodi di siccità prolungata e le inondazioni sempre più frequenti dovuti al cambiamento climatico stanno causando perdite di vite umane, biodiversità e infrastrutture. Il sistema energetico, in quanto responsabile dei tre quarti delle emissioni planetarie di gas serra, non può più avere come soli obiettivi l’aumento dell’efficienza e la riduzione dei costi a breve termine. Libro stampato a colori.
Nel testo sono illustrate le fonti primarie esauribili che hanno contrassegnato l’epoca industriale, le fonti rinnovabili tradizionali e moderne e infine le strategie e le tecnologie necessarie per decarbonizzare il sistema energetico attuale, giustificando il ruolo prioritario che dovrà avere la generazione di energia elettrica in eccesso rispetto alle esigenze di oggi e il ruolo non secondario che dovrà essere affidato all’idrogeno. L’appendice, con i piani proposti dall’Agenzia Internazionale dell’Energia (IEA) presente le misure che saranno necessarie per ridurre le importazioni di gas naturale e petrolio dalla Russia
Applications of Coupled Heat and Moisture Transfer Simulations in Buildings
Get PDFThe uncontrolled presence of moisture in building envelopes and structures could be the cause of several typologies of damages (for example freeze-thaw cycles damage or corrosion of metal reinforcements) and health and safety hazard for the occupants (mould and fungi growth).
Several heat and moisture transfer models could be used to simulate the phenomenon and, using the damage criteria, to predict the failure of the building envelopes or structures.
Some commercial software tools are available to the practitioners but, not all the material producers provide the advanced hygrothermal material parameters necessary to perform the simulations. Moreover, the proper weather files that should be used to calculate the boundary conditions for the simulations are rarely available.
In this thesis, the models implemented in the commercial software tools are presented and some of the limits met in the simulation process, mostly regarding material parameters and the weather files, have been studied and analysed.
First, a practical comparison between the widespread Glaser method, a simplified stationary method for the evaluation of the interstitial condensation, and a transient coupled heat and moisture transfer model is presented, underlining the limitations of the simplified method.
With respect to the hygrothermal material parameters limitations, two simple experimental procedures for the evaluation of the material properties are presented. The obtained values are found to be consistent with the experimental results by a comparison with the simulation.
Then, the influence of hysteresis on the transient hygrothermal behaviour of a cross-laminated timber wall is presented, showing that by considering the hysteresis in the model, the quantity of moisture retained in the structures during a year changes.
Regarding the boundary conditions, the procedures for the statistical selection of representative weather files - used to model the typical weather of a location - and the reference weather files - designed to represent the critical weather conditions of a location - are presented. The study has been undertaken on the typical building envelopes for different locations of Northern Italy
Development of an energy digital twin from a hotel supervision system using building energy modelling
Get PDFIn this work, the utilization of the supervision system of a five-story hotel located
in Northern Italy as tool to calibrate and validate a building energy model (BEM) is evaluated.
The BEM is created using the TRNSYS simulation environment with the aim to develop a
digital twin, to study the energy consumption of the building-HVAC system. The procedure for
the supervision system preparation and the data analysis procedure is presented. The digital
twin is then used to compare two control strategies for the thermostats’ control during summer
to increase the energy efficiency of the building-HVAC system, and to use the heat storage
properties of the building envelope to shift and shave the peaks of power demands. Control
rules that allow a better match between electrical energy demand and availability, developed,
and tested using the BEM, are pursued with the final goal to prepare the inclusion of the hotel
in a smart grid. The building is modelled using TRNSYS Type 56 as a multi-zone building,
with 96 thermal zones while the building monitoring is performed during the summer season
from June to October 2022
Numerical simulations of coupled conduction-free convection in low conductive vertical finned surfaces
No full textHVAC coverage in integrated refrigeration systems at various climate and building conditions
Get PDFFood retail applications offer a unique opportunity to improve the performance of pure CO2 refrigeration sys-
tems, i.e. the integration of all the thermal functions in a compact “fully-integrated” unit, capable of providing
refrigeration capacity at two temperature levels for chilled and frozen products, hot water production, space
heating and cooling for the supermarket. Many factors determine the economic advantage of such a solution. A
case study of a transcritical CO2 integrated refrigeration system for a 1200 m2 supermarket with back up heat
pumps is taken as an example and several scenarios are investigated. A comprehensive model in TRNSYS with in-
house types, validated with field data from a fully instrumented plant located in Northern Italy, allows a thermal
dynamic simulation of the building with its interaction with display cabinets, the estimation of the refrigerating
loads of display cabinets and cold rooms, and the behaviour of the commercial refrigeration unit and heat pumps.
The goal is to investigate the coverage limits and global energy use for six climate zones and various load ratios,
thus considering also different sales areas and construction types of the building. It is proven that such integrated
solution can effectively cover also space cooling needs in a range from 95 to 100 % and space heating from 83 %
to 100 %, provided an additional outside evaporator is installed especially for coldest climates and higher
heating requests. In all but one case, the integrated system is more advantageous than the separate solution, with
total electrical energy savings ranging from a few percentage points to 10.5 %
Near infrared technology for material identification and selection
No full textThe increasing demand for recycled wood to produce particleboard and MDF panels has resulted in the need to improve the cleaning process of post-consumer material, eliminating in a more effective and efficient way plastic impurities. We have developed a new method based on the NIR diffuse reflectance spectral analysis for the identification of different classes of materials that can be used in the selection process.
We have investigated the diffuse reflected light in the range 1100 - 2500 nm of a wide sample of materials including plastics, ceramics, tiles, woods and laminates as representative of garbage dump materials. We have considered the typical features of the different classes of materials and looked for those spectral regions that present some difference among the classes. We have studied the correlation among the various features characterizing the spectra of each class and identifying the spectral bands potentially most effective in the discrimination process. Accordingly, six indices able to distinguish different materials have been defined. The results show that the near infrared spectral analysis can be used as an efficient analytical technique to identify different objects facilitating rapid separation process
Generation Of Moisture Reference Years For Interstitial Condensation Risk Assessment: Influence Of The Meteorological Record Length
Get PDFHeat, air and moisture (HAM) transfer simulations used in moisture accumulation risk assessment of building envelopes require adequate weather files. The common approach is to use weather data of reference years constructed from meteorological records. The length of the records affects the capability of representing the real weather of the resulting reference years. In this paper the problem of the influence of
the length of the records on the representativeness of the reference years is addressed and an evaluation of the effect on the moisture accumulation risk analysis with the Glaser Method and with Delphin is presented confirming that records shorter than 10 years could lead to less representative reference years. An alternative reference year (Moisture Reference Year) for moisture related simulations is presented and, the
results for the considered weather stations show that it is possible to use it as a representative year for the moisture accumulation risk evaluation
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