有限要素法によるボイドスラブの非定常伝熱解析-1-ボイド内部が自然対流の場合について

概要

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Void slab is defined as slab which has many parallel air spaces (voids) in it. Usually, the void has a circular or a rectangular cross section in the slab which is, approximately, 40 cm thick. The floor heights of the void slab buildings are less than those of conventional buildings, because they require no beams. Sometimes, the voids are used as duct spaces. Furthermore, the noise insulation effect of the void slab is large. Recently, the advantages of void slabs have been widely recognized. However, their thermal behaviors, as yet, have not been clarified. In this paper, transient heat flow, surface temperature and void air temperature are calculated using a finite element method combined with a finite difference method. The void surface coefficients are treated as strictly as possible in the calculations: not only the surface convective coefficient αc is treated as a TVP (time variable parameter), which changes with heat flow direction and temperature difference between void air and void surface, but also the surface radiative coefficient αr is dealt with as a TVP and is derived using Gebhart's absorption factor. The calculated transient heat flux and temperature of void slabs are compared with those of conventional slabs.