Spectral emissivity of anodized aluminum and the thermal transmittance of aluminum window frames

摘要: Heat transfer in window frames with internal air cavities is studied this thesis. Investigations focus on two- and three-dimensional natural convection effects inside cavities, the dependence of emissivity thermal transmittance, anodized untreated aluminum profiles. The investigations are mostly conducted which same size as real found residential buildings.Numerical experimental were performed to study effectiveness one commercial Computational Fluid Dynamics (CFD) program for simulating combined heat simple cavities. accuracy conjugate CFD simulations was evaluated by comparing results surface temperature warm side specimens from experiments that use infrared (IR) thermography map temperatures during steady-state tests. In general, there good agreement between experiments. Two-dimensional computational fluid dynamics conduction difference treating a solid when calculating transmittance frames. show traditional software codes, only using equivalent conductivities give U- values compare well flow simulations. two models limited distribution It also an interconnection less than about 7 mm can be treated separate Three-dimensional custom-made PVC thermally broken open cavity studied, Focus put corner rates. From it appears four-sided section average respective single horizontal vertical sections. addition, two-dimensinal simulation agrees tree-dimensional if correlations used correct. Numerical studies done high aspect ratio low ratio. had ratios 20, 40, 80 ranging 0,2 5. shown larger five considered two-dimensional within 4 % considering Nusselt number different presented 20 40. Complex multicellular case where 40 2, respectively.Experimental included normal spectral total six meter long Specimens facing (thermal break all cavity) measured. Some masking tapes often hot box fairly constant (between 0.834 0.856) exterior parts profile surfaces cavity. all-aluminum vary 0.055 0.82. Fourier transform spectrometer wavelength interval 4.5 μm.