The object of this thesis is the external shading devices, so extremely important to reduce summer loads and to adjust the lighting comfort inside buildings. The aim is to examine the optical properties for those types whose geometry can provoke significant differences in the value of solar coefficients at 0° or increasing the angle of incidence of solar radiation. For this purpose some metal meshes, micro perforated steel plates and technical fabrics present on the market were analyzed. At first a study on solar design and on methods nowadays frequently used to measure the performance of shielding was presented. In addition were explained the applications on façade, the production process and characteristics of metal meshes, micro perforated steel plates and technical fabrics. Experiments were carried out at the centre Enea with the Ulbricht sphere and spectrophotometer to measure the hemispheric transmission, reflection and absorption properties along the solar spectrum. As a consequence, were obtained the average solar coefficients for angles of incidence 0 °, 30 °, 45 ° and 60 °. A daily profile of luminous transmittance was then traced for each screening, orientation and season, for a façade placed in Milan. Subsequent simulations through Radiance software made it possible to create reliable models of some of these shadings. The results of experiments and simulations prove the presence of a strong variation of the transmission properties of the solar transmission, and consequently of the g value, moving up from 0° to 60° degrees. This discrepancy can be significant especially during the hottest hours of the day that are associated with a greater angle. Calculate the solar gains of some shading devices, such as those submitted, in accordance with the criteria presented in the standards would lead to an overestimation of these values. This work can be seen as a first step towards a more detailed analysis of sunscreens and provides a method to evaluate their actual solar properties.
Il presente elaborato di tesi ha come oggetto le schermature solari esterne che sono di estrema importanza per ridurre i carichi estivi e regolare il comfort luminoso all’interno degli edifici. L’obiettivo è quello di vagliarne le proprietà ottiche per quelle tipologie aventi una geometria tale da poter presentare forti differenze in termini di coefficienti solari al variare dell’angolo di incidenza solare. A tale scopo sono state analizzate alcune maglie metalliche, lamiere microforate e tessuti tecnici presenti sul mercato. Inizialmente è stato presentato uno studio sulla progettazione solare e sui metodi oggigiorno frequentemente utilizzati per misurare le prestazioni delle schermature solari. Sono state poi mostrate le applicazioni, il processo produttivo e le caratteristiche delle maglie metalliche, delle lamiere microforate e dei tessuti tecnici. Sono stati effettuati esperimenti al centro Enea con una sfera di Ulbricht e con uno spettrofotometro per misurare le proprietà emisferiche di trasmissione, riflessione e assorbimento lungo lo spettro solare. Grazie a ciò si sono ricavate i coefficienti solari medi per gli angoli di incidenza 0°, 30°, 45° e 60°. E’ stato poi tracciato un profilo di trasmittanza luminosa giornaliera per ogni schermatura, orientamento e stagione, per una facciata situata a Milano. Simulazioni successive attraverso il software Radiance hanno permesso di creare modelli attendibili di alcune di queste schermature. I risultati degli esperimenti e delle simulazioni confermano la presenza di una forte variazione delle proprietà di trasmissione e quindi del fattore solare spostandosi dalla normale fino a 60°. Questa discrepanza può risultare significativa soprattutto nelle ore più calde della giornata con angolo maggiore. Calcolare gli apporti solari gratuiti di alcune schermature come quelle presentate seguendo i criteri presentati dalla norma porta a una sovrastima di tali valori. Questa tesi si pone come un primo passo verso una trattazione più particolareggiata delle schermature solari e offre un metodo per vagliarne le effettive proprietà solari.
Protezioni solari sottili. Misura e modellazione delle prestazioni ottiche
BIROCCHI, MATTEO
2011/2012
Abstract
The object of this thesis is the external shading devices, so extremely important to reduce summer loads and to adjust the lighting comfort inside buildings. The aim is to examine the optical properties for those types whose geometry can provoke significant differences in the value of solar coefficients at 0° or increasing the angle of incidence of solar radiation. For this purpose some metal meshes, micro perforated steel plates and technical fabrics present on the market were analyzed. At first a study on solar design and on methods nowadays frequently used to measure the performance of shielding was presented. In addition were explained the applications on façade, the production process and characteristics of metal meshes, micro perforated steel plates and technical fabrics. Experiments were carried out at the centre Enea with the Ulbricht sphere and spectrophotometer to measure the hemispheric transmission, reflection and absorption properties along the solar spectrum. As a consequence, were obtained the average solar coefficients for angles of incidence 0 °, 30 °, 45 ° and 60 °. A daily profile of luminous transmittance was then traced for each screening, orientation and season, for a façade placed in Milan. Subsequent simulations through Radiance software made it possible to create reliable models of some of these shadings. The results of experiments and simulations prove the presence of a strong variation of the transmission properties of the solar transmission, and consequently of the g value, moving up from 0° to 60° degrees. This discrepancy can be significant especially during the hottest hours of the day that are associated with a greater angle. Calculate the solar gains of some shading devices, such as those submitted, in accordance with the criteria presented in the standards would lead to an overestimation of these values. This work can be seen as a first step towards a more detailed analysis of sunscreens and provides a method to evaluate their actual solar properties.| File | Dimensione | Formato | |
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2012_09_Birocchi.pdf
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Descrizione: Testo della Tesi
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https://hdl.handle.net/10589/68041