Three-dimensional numerical simulation of conduction, natural convection, and radiation through alveolar building walls

•Three-dimensional numerical simulation of conduction, natural convection and radiation heat transfers through alveolar.•A numerical method is used to predict the thermal performances of concrete blocks.•The conservation equations and the radiative exchanges amongst surfaces are solved.•Comparison with the thermal resistance given in Th-U is discussed for two kinds of concrete block. Numerical simulation of the coupled heat transfers by conduction, convection, and radiation through two kinds of the alveolar structures used in the construction are numerically investigated. Owing to the low-temperature differences involved, the tridimensional model is based on the Boussinesq approximation and constant thermophysical fluid properties at mean temperature. The alveolar walls are assumed grey and diffuse. The symmetric and periodic boundary conditions for flows governed by the incompressible Navier-Stokes equations are considered. Equations governing the natural convection in the alveolars, the radiative heat exchanges between their internal surfaces and the heat conduction in the surrounding walls are solved using a finite volume method. The pressure-velocity coupling is solved by SIMPLE algorithm. The objective of this study is to improve the effects of wall conduction and radiation heat exchange between surfaces on the decrease of the thermal resistance in the alveolar walls. Two kinds of concrete blocks with three and six-hole numbers are chosen and their thermal resistances are numerically predicted. The comparison between the thermal resistances, specified in terms of thermal regulations for buildings and numerical solutions, is presented.