Analysis of Heat Conduction of Anisotropic Building Materials

Abstract

Heat conduction in anisotropic materials is quite different from that in isotropic materials. Heat flux vector is commonly not perpendicular to the isothermal surface in anisotropic materials. The advantage and disadvantage of anisotropic materials were analyzed in this paper. The thermal conductivities at one point are not equal in all directions for anisotropic materials. The technique of double skin facade has been successfully applied in many building designs. The application of combining building envelope of anisotropic materials and double skin facade was proposed to avoid its disadvantage. Basing on the combination of anisotropic materials and double skin facade in building envelope, the indoor cooling and heating load decrease in summer and winter respectively. Especially in summer, the effect of energy saving is obvious since the partial magnitude of conductive heat in the envelope made of anisotropic materials could be brought out from the cavity of double skin facade by natural or forced ventilation through it.

Assessment of Seasonal Energy Efficiency Strategies of a Double Skin Façade in a Monsoon Climate Region

“…In winter, it would be advantageous in terms of thermal comfort to close the openings since external temperature is always lower than inside the building. Existing studies and cases have shown that, as mentioned in the introduction, the static air buffer is the optimal type in winter because it acts as a thermal buffer [9][10][11][12][13][14][15]38] (Figure 3a). …”

“…In winter, the heat in the cavity can considerably reduce the heating load of a building in terms of thermal comfort. Particularly, in winter, conducting the heat in the cavity to the building's interior can be maximized by using a static air buffer as an airflow operating method, which seals the heat in the cavity [9][10][11][12]. The Telus Headquarters building in Toronto and the Occidental Chemical buildings in Niagara Falls and in New York use a static air buffer as an airflow operating method to reduce heating energy consumption in winter [13].…”

“…Various studies have been conducted on the airflow operating methods in implemented during summertime. It has been shown that the external air curtain as an airflow operating method that opens the openings in the cavity (i.e., allowing the heat in the cavity to travel freely outside) would save cooling energy consumption during summer because the heated air in the cavity due to solar radiation could be removed in advance before being transmitted to a building [9,[12][13][14]. To discharge the heated air in the cavity and the building to outside the building, natural ventilation, as well as the external air curtain, are also considered important [7,[18][19][20][21].…”