Thermal modeling of the convective heat transfer in the large air cavities of the 3D concrete printed walls

The cavity walls are a widely used construction system. They became popular in traditional masonry construction for their capacity to reduce the passage of moisture and improve the walls' thermal performance. However, the latter only applied to narrow cavities with restricted internal air movement. Cavities are also present in emerging technologies, such as 3D concrete printed walls. However, the large cavities of the 3D printed concrete walls have high convective heat transfers that affect the envelope's thermal performance. Therefore, the authors developed a conjugate heat transfer finite element model to study the large cavities in 3D printed concrete walls and determine the effect on the convective heat transfer of subdividing large cavities. The results show it is possible to reduce the heat flux four times, from 40.4 W/m2 to 9.1 W/m2, subdividing a large cavity into sixteen small ones. This reduction might be higher, increasing the number of cavity subdivisions. However, it is infeasible to restrict the air movements in unfilled air cavities over 25 mm wide for the Rayleigh numbers >= 10(5). Therefore, the practicality of minimizing heat transfer by subdividing large air cavities in 3D printed walls is limited.

Automated summary

Cavity walls are commonly used in construction to reduce moisture and improve thermal performance. However, large cavities in 3D printed concrete walls have high convective heat transfers that affect thermal performance. The study shows that subdividing large cavities into smaller ones can significantly reduce heat transfer.