Research Article Building Thermal, Lighting, and Acoustics Modeling E-mail: abdelbaki@ucam.ac.ma Numerical simulation by the FVM of coupled heat transfers by conduction, natural convection and radiation in honeycomb's hollow bricks Mohammed Boukendil, Abdelhalim Abdelbaki (), Zaki Zrikem LMFE, Department of Physics, Cadi Ayyad University, Faculty of Sciences Semlalia, B.P. 2390, Marrakesh, Morocco Abstract This paper presents a detailed numerical study, in steady state regime, of the interaction between two dimensional heat transfers by conduction, natural convection and radiation in double hollow bricks formed by two honeycomb walls separated by an air layer. The air motion in all cavities of the system is laminar. The left and right vertical sides of the hollow bricks are considered isothermal and maintained at different constant temperatures. The top and bottom horizontal sides are assumed to be adiabatic. The governing equations are solved using the finite volume method (FVM) and the SIMPLE algorithm. The impact of the thickness of the air layer on the global heat flux through the structure is discussed. The simulation results show that the variation of the overall heat flux through each hollow brick as a function of the temperature difference ΔT between the vertical sides of the system is almost linear for the different types of double hollow bricks considered. This linear thermal behaviour allowed the generation of appropriate overall heat exchange coefficients that permit fast and accurate prediction of heat transfers through the hollow bricks without solving the complex system of equations governing the coupled heat transfers. Comparison of the performance of different types of double hollow bricks is made. Keywords hollow brick, conduction, natural convection, radiation, thermal conductance, numerical simulation Article History Received: 7 August 2009 Revised: 12 October 2009 Accepted: 23 October 2009 © Tsinghua University Press and Springer-Verlag 2009 1 Introduction Last years, the use of hollow bricks in building envelops is in full expansion. In fact, such components permit significant reduction of heat transfer through the building envelops and reduce considerably the heat load of heating and air- conditioning. The heat transfer within hollow blocks is done simul- taneously by conduction in the different solid partitions, natural convection inside the holes and radiation between the internal faces of the holes. These three heat transfer processes are intimately bound. Therefore, accurate numerical study of the thermal behaviour of the hollow bricks needs a simultaneous resolution of the complex, nonlinear and coupled equations governing the different thermal transfer’s mechanisms. In the literature, a lot of works were made on the coupling between the heat transfer processes. Earlier investigations were conducted by Balvanz and Kuehn (1980), Kim and Viskanta (1984) on the interaction between the natural convection in a square cavity and the heat conduction in the adjacent walls. Effects of surface radiation on natural convection in square enclosures filled with air were studied by Balaji and Venkateshan (1993, 1994), Akiyama and Chong (1997), Ramesh and Venkateshan (1999), Ramesh et al. (1999). In these studies, it has been shown that natural convection heat transfer is significantly reduced by conduction in the walls and/or radiation exchange between the cavity surfaces. Coupled heat transfers by conduction, natural convection and radiation in cellular structures with two vertical series of square cavities has been studied numerically (Abdelbaki and Zrikem 1999). Application was presented for building vertical walls made of hollow clay tiles. Later, numerical solution of combined heat transfers in hollow clay tiles, with two air cells deep, submitted to transient thermal BUILD SIMUL (2009) 2: 263 – 272 DOI 10.1007/s12273-009-9123-2