Dimension optimization of two air cavities thermal insulator as an application in buildings

• Published in: Heat transfer, Asian research Asian research, 2018-12, Vol.47 (8), p.996-1030
• Main Authors: Elnaggar, Mohamed, Alnahhal, Mohammed, Edwan, Ezzaldeen
• Format: Article
• Language: English
• Subjects: Aspect ratio; Buildings; cavity dimension optimizations; cavity insulators in buildings; cavity thermal insulation; conjugate conduction—natural convection heat transfer; Holes; Nusselt number; thermal diffusivity
• ISSN: 1099-2871; 1523-1496
• DOI: 10.1002/htj.21362

The present study investigates the use of two air cavities thermal insulator in buildings. The two air cavities insulator structure is supposed to be located within the building's wall and roof forming two separated vertical and horizontal cavity, respectively. In addition, the wall cavity height (or roof cavity length), H, was investigated at H = 2, 3, 4, 5 m to find the influence of wall cavity height (or roof cavity length) on various thermal characteristics and thus to determine the thermal optimum thickness. At each wall cavity height (and roof cavity length), cavity thickness, Lc, was varied from 0.01 m to 0.1 m forming aspect ratio, AR = H/Lc ranges of 20 to 200, 30 to 300, 40 to 400, and 50 to 500 for H = 2, 3, 4, and 5 m, respectively. The present results reveal the presence of the first and second cavities in wall and roof at various thicknesses affecting the development of wall and roof components' surface temperature. In addition, varying the wall cavity height or roof cavity length has further significant effects on the development of these surface temperatures. Moreover, it was found that increasing the wall cavity height leads to increasing the optimum wall cavity thickness, Lc = 0.024, 0.027, 0.029, and 0.031 m at cavity height, H = 2, 3, 4, and 5 m, respectively, whereas in the roof cavity case, the optimum roof cavity thickness seems to reach its asymptotic value at about 0.019 m for the roof cavity length investigated, H = 2, 3, 4, and 5 m despite the optimum wall cavity thickness that was not.