Improving the thermal performance of red clay holed bricks

• Holed bricks with internal protuberances having improved performance as thermal insulators.
• Smart holed bricks, acting as better thermal insulators when operating under higher temperature differences.
• Modified holed bricks allowing considerable energy savings in buildings.

A numerical study is conducted to improve the thermal performance of red clay holed bricks, considering protuberances to inhibit natural convection and radiation heat transfer inside the brick holes. Protuberances are made of the same red clay and have the same thickness as the remaining elements of the bricks, the best solution leading to the lowest overall heat transfer rate with shorter protuberances. Protuberances increase conduction heat transfer but decrease natural convection and radiation heat transfer, and a minimum overall heat transfer exists. Protuberances allow an overall heat transfer reduction which increases as increases the Rayleigh number. For fixed solid material (red clay) and fluid (air), the Rayleigh number depends mainly on the temperature difference between the opposite faces of the brick. For increasing temperature differences, when the thermal performance of the buildings’ walls is more important, protuberances increasingly improve the thermal performance of the bricks, giving to the bricks a smart character. Relevant information is obtained, helping holed bricks makers to obtain better bricks for energy savings and energy consumption reductions in buildings, the obtained results leading to overall heat transfer reductions up to 23%. Some comparisons are made with experimental results for common and commercially available red clay holed bricks without protuberances.