The purpose of this work is analyzing the thermal performances of thin reflective insulation products (ISR), used as building components, in order to choose the best materials and constructive configurations, suitable for good thermal performances. In order to determine the thermal resistance provided by a multilayer reflective system, considering the material itself and including the air gaps as well, in different configurations of the building system and with variation of thermo physical and dimensional properties of the multilayer element, a complete sensitivity analysis has been carried out. The study of the heat exchange phenomenon through the multilayer reflective element was carried out by developing and comparing several modeling levels: a concentrated parameters model, composed by semitransparent and opaque layers; one-dimensional numerical model able to simulate the conduction and radiation phenomena inside a layer with a participating medium and a two-dimensional CFD model able to simulate the entire multilayer element. The results of the parametric analysis allowed us to evaluate the thermal resistance of the insulation, varying the emissivity of the reflective films and the infrared absorption of the materials used in the multilayer elements, in particular the convenience to increase the number of reflective films, depending on the infrared transparency of the interposed layers.
Oggetto del seguente lavoro è l’analisi delle prestazioni termiche di isolanti sottili riflettenti (ISR) utilizzati come componenti dell’involucro edilizio, al fine di scegliere i materiali e le configurazioni costruttive ottimali per la resa delle prestazioni termiche. È stata quindi condotta un’analisi di sensitività per determinare la resistenza termica fornita dal sistema composto dal multistrato riflettente e dalle intercapedini d’aria all’interno di diverse configurazioni del sistema edilizio e al variare delle proprietà termofisiche e dimensionali del pacchetto multistrato. Lo studio dello scambio termico attraverso il multistrato riflettente è stato effettuato sviluppando e confrontando diversi livelli di modellazione: un modello a parametri concentrati composto da strati semitrasparenti e strati opachi, un modello numerico monodimensionale in grado di simulare la conduzione e la radiazione all’interno di uno strato con mezzo partecipante ed un modello CFD bidimensionale in grado di simulare l’intero multistrato. I risultati dell’analisi parametrica hanno permesso di valutare la resistenza termica dell’isolante al variare dell’emissività delle pellicole riflettenti e dell’assorbimento nell’infrarosso dei materiali usati nel multistrato, e in particolare la convenienza dell’aumento del numero di pellicole riflettenti in funzione della trasparenza all’infrarosso degli strati interposti.
Analisi parametrica delle prestazioni termiche di isolanti sottili riflettenti
PESANDO, CHIARA;LEONI, ALESSANDRA
2010/2011
Abstract
The purpose of this work is analyzing the thermal performances of thin reflective insulation products (ISR), used as building components, in order to choose the best materials and constructive configurations, suitable for good thermal performances. In order to determine the thermal resistance provided by a multilayer reflective system, considering the material itself and including the air gaps as well, in different configurations of the building system and with variation of thermo physical and dimensional properties of the multilayer element, a complete sensitivity analysis has been carried out. The study of the heat exchange phenomenon through the multilayer reflective element was carried out by developing and comparing several modeling levels: a concentrated parameters model, composed by semitransparent and opaque layers; one-dimensional numerical model able to simulate the conduction and radiation phenomena inside a layer with a participating medium and a two-dimensional CFD model able to simulate the entire multilayer element. The results of the parametric analysis allowed us to evaluate the thermal resistance of the insulation, varying the emissivity of the reflective films and the infrared absorption of the materials used in the multilayer elements, in particular the convenience to increase the number of reflective films, depending on the infrared transparency of the interposed layers.File | Dimensione | Formato | |
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https://hdl.handle.net/10589/44522