In Italy most buildings built before the seventies have external walls of low heat storage capability and of low thermal insulation level. The solution proposed in this work to improve the performance of these walls, is a retrofit by means of a layer of Phase Change Material (PCM). This technology is of particular interest because can contribute effectively to reduce the risk of overheating, to reduce the high cooling demand, with significant energy saving, and to improve the comfort, during the summer. The goal of this paper is the analysis of the energy behaviour of a conventional wall, where on the outer surface a thin layer of PCM is applied. In the analysis a control volume code is used. The external conditions are referred to a typical summer day. The performance of the storage systems are evaluated by comparison between a conventional wall and the same after the suggested retrofit. In the comparison the dynamic thermal characteristics, decrement factor and time shift, as suggested by EN ISO 13786, are used. The analytical solution proposed by the same standard is also used, when possible. For the conventional wall both the numerical and analytical results are used to obtain the dynamic thermal characteristics. For the wall with the PCM cover just the numerical can be used. The results show the effectiveness of the solution adopted, but make evident that the dynamic thermal characteristics of the wall with the layer of PCM are dependent on the boundary conditions. Finally the applicability of the EN ISO 13786 to this innovative kind of retrofit has been evaluated.
INVESTIGATION ON THE DYNAMIC BEHAVIOUR OF A WALL WITH A LAYER OF SOLID-LIQUID PHASE CHANGE MATERIAL
CASANO, Giovanni;MATTARELLI, Agnese;PIVA, Stefano
2010
Abstract
In Italy most buildings built before the seventies have external walls of low heat storage capability and of low thermal insulation level. The solution proposed in this work to improve the performance of these walls, is a retrofit by means of a layer of Phase Change Material (PCM). This technology is of particular interest because can contribute effectively to reduce the risk of overheating, to reduce the high cooling demand, with significant energy saving, and to improve the comfort, during the summer. The goal of this paper is the analysis of the energy behaviour of a conventional wall, where on the outer surface a thin layer of PCM is applied. In the analysis a control volume code is used. The external conditions are referred to a typical summer day. The performance of the storage systems are evaluated by comparison between a conventional wall and the same after the suggested retrofit. In the comparison the dynamic thermal characteristics, decrement factor and time shift, as suggested by EN ISO 13786, are used. The analytical solution proposed by the same standard is also used, when possible. For the conventional wall both the numerical and analytical results are used to obtain the dynamic thermal characteristics. For the wall with the PCM cover just the numerical can be used. The results show the effectiveness of the solution adopted, but make evident that the dynamic thermal characteristics of the wall with the layer of PCM are dependent on the boundary conditions. Finally the applicability of the EN ISO 13786 to this innovative kind of retrofit has been evaluated.I documenti in SFERA sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
