Numerical simulation of concrete hollow bricks by the finite volume method

Numerical thermal analysis has become a powerful tool for hollow brick design concerning energy saving issue. In the present paper it was employed to understand the heat transfer performance of 240 × 115 × 90 concrete hollow bricks with 71 different configurations. The general commercial computational fluid dynamics (CFD) soft FLUENT® was used in the research. A comprehensive investigation on the effect of enclosure configurations with the same void volume fraction on equivalent thermal conductivity (ETC) was conducted. The enclosure numbers in parallel and vertical directions of heat transfer were investigated in details. The effect of enclosure staggered form is also discussed carefully. In the research, ETC data was compared with radiation and nature convection and without them. In addition, temperature and velocity vector distributions were also illustrated in order to clarify heat transfer mechanism. It can be concluded from this research that ETC values are dependent on the combining effect of heat conduction in all domains, natural convection within enclosure and radiation on inner surface. ETC values decrease with the increasing enclosure numbers in the parallel direction of heat transfer and increase in the vertical direction of heat transfer, vise versa. Therefore, increasing enclosure numbers in the parallel direction becomes more favorable to decrease ETC than that in the vertical direction of heat transfer. Secondly, the relative enhancement of radiation heat transfer on ETC ranged from 7.41% to 25.39%, and the nature convection from near zero to 22.50%, depending on the enclosure numbers and their arrangement configurations. Finally, the increasing enclosures in the parallel direction can decrease ETC values from 11.59% to 20.94% for enclosure vertical aligned bricks. Under the given conditions the smallest ETC is 0.32619 W/(m K) for enclosure staggered form with three enclosures in length direction and eight in width direction, which is only 23.30% of the solid concrete brick in the present research.