Numerical computation of buoyant airflows confined to attic spaces under opposing hot and cold wall conditions

Abstract

The present paper addresses laminar natural convection of air confined to an isosceles triangular cavity representative of conventional attic spaces in houses and buildings with pitched roofs and horizontal suspended ceilings. Detailed experimental data in terms of velocities, temperatures and wall heat fluxes has become available for attic spaces under summer and winter conditions some time ago. However, the comparison between the numerical-obtained temperatures and mean wall heat fluxes against the experimental-measurements is still lacking in the specialized literature. Two relevant cases of isosceles triangular cavities are considered: case 1, the base is cooled and the two inclined walls are symmetrically heated and case 2, the bottom base is heated and the two top inclined walls are symmetrically cooled. To perform the computational analysis, the finite volume method is the vehicle for the discretization of the conservation equations. The Boussinesqian fluid approximation is not invoked and all thermophysical properties are taken as temperature-dependent. Most numerical simulations have assumed the existence of a vertical plane of symmetry passing through the middle of the isosceles triangular cavity in order to deal with a manageable computational domain in the form of a right-angled triangle that is half the size of the isosceles triangular cavity. However, the computational domain adopted in this work has been taken as coincident with the physical domain. Overall, the numerical predictions of velocity, temperature and mean wall heat fluxes match reasonably well with the experimental measurements for the two cases under study here.