Numerical simulation of coupled heat transfer through double hollow brick walls: Effects of mortar joint thickness and emissivity

Abstract

Combined heat transfer by conduction, natural convection and surface radiation in two-dimensional double hollow brick walls including an air layer was numerically studied. Finite volume procedure based on the SIMPLE algorithm has been used to solve the governing equations. The air motion in all cavities of the system is laminar. The outer and inner surfaces of the double hollow brick walls are considered isothermal and the two horizontal surfaces are supposed adiabatic. Based on the simulation results, the convective coefficient (hc), the radiative coefficient (hr) and the thermal resistance (Rg) of the air layer were generated. The effects of mortar joint thickness and the emissivities of the surfaces of the air layer and the hollow bricks on the heat transfer through the structure were predicted for different values of the temperature difference (ΔT) that occurs in practice between the outer vertical surfaces of the structure. The results showed that using a mortar joint thickness equal to 1cm is a good compromise to estimate the thickness needed to join the hollow bricks. This mortar thickness combined to a low emissivity of the structure surfaces would greatly help in reducing the energy consumption of buildings.