Author(s) :

Ola Kamiyo.

Volume/Issue :

Abstract :

Attic spaces of residential as well as industrial pitched-roof buildings are commonly of triangular shape. Most of the past studies on free convection within such spaces have focused on the isosceles triangular shape with few on complex shapes. Combination triangular shape is one of the complex shapes commonly found in attics of modern buildings. A finite volume analysis of laminar natural convective heat transfer in combination-shaped rooftops has been studied. Two sets of boundary conditions have been considered: enclosure heated from the horizontal bottom wall, and enclosure heated from the inclined top walls, for pitch angles 140, 200, 250 and 350for 106 Ra 2.7 x 107. The complex shape of the enclosure affects the structure of the flow and temperature fields. For the enclosures heated from below, at low Ra, quasi-symmetric flow was observed. A large central vortex drives smaller counter-rotating cells whose number and strength changes as the pitch angle increases. At low pitch, multi-cellular flow structure formed results in uniform temperature due to thorough mixing of air. As the aspect ratio increases, the heat transfer coefficient decreases with mean temperature tending towards that of the cold wall. Mean Nusselt number is directly proportional to the Rayleigh number. When the enclosures are heated from above, there is essentially symmetric thermo-fluid solution with thermal stratification limited to the lower part in most enclosures. The results are useful in thermal management of combination-shaped enclosures and pitched roofs.

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