Application of a wall-solar chimney for passive cooling of dwellings

Energy consumption is an important issue and has become a great concern during last the few decades, where most energy consumption is utilized for conditioning buildings. The solar chimney is a natural ventilation technique that has the potential to save energy use in buildings as well as maintain comfortable indoor quality. The objective of the current study is to examine the effects of the wall-solar chimney on airflow distribution and thermal conditions in a room. In the current work, computational fluid dynamics was used to model a solar chimney. The time-dependent conservation equations for mass, momentum and energy were solved with the k-ε turbulence equations using ANSYS Fluent. Previous literature, that utilized numerical modeling to study the solar chimney for different dimensions of chimney geometry, only considered a twodimensional solar chimney with one-directional heat transfer. In the current study, the solar chimney was modeled threedimensionally for a more realistic simulation of actual flow and thermal condition of the room. Experimental and numerical data from literature were used to validate the current model, and the results agreed very well. The current study showed that the flow in the solar chimney system can be either laminar or turbulent depending on the parameters of the system, and that the effect of the chimney inlet is more significant than that of the air gap on the flow regime. This study also developed a new characteristic Rayleigh number Ra∗ relating the chimney inlet and the air gap, which showed good consistency with the prediction of the flow regime. The investigations on Ra∗ and the flow regime indicated that the flow becomes turbulent for Ra∗ ∼ 0.8 × 10⁸. Lastly, the potential improvements of the designs were discussed by observing the flow and thermal condition of the room.