Numerical simulation and exergetic analysis of building ventilation solar chimneys

• Exergetic analysis of a building ventilation solar chimney.
• Numerical CFD model developed, validated and employed to study the flow.
• Analysis of the solar chimney energy and exergy efficiencies.
• Mechanical and thermal exergy distributions have been analysed.
• Crucial points in the chimney identified to improve its performance.

The solar chimneys used in buildings are passive solar devices which improve natural ventilation. A detailed exergetic analysis has been developed in this work, both for general balance and specific variables. To apply this analysis, a three-dimensional CFD model has been built and validated with bibliographic experimental data. The values of the variables have been examined both inside and at the exit of the solar chimney, resulting in a detailed description of the inner phenomena and parameters influencing the exergetic efficiency. The results of this study offer new tools: a numerical methodology and an exergetic analysis, to improve the design of building ventilation solar chimneys. It also affords a deeper understanding of the thermal and fluid-dynamic behaviour, and suggests some qualitative improvements. However, the numerical data obtained from the case studied, show that solar chimneys as natural ventilation systems offer quite a small efficiency and will remain within the sphere of architectural decisions.