Passive cooling and natural ventilation by the windcatcher (Badgir): An experimental and simulation study of indoor air quality, thermal comfort and passive cooling power

Abstract

The upper wing wall can be integrated into the windcatcher to prevent direct solar and rain penetration. The impact of this combination was not considered in previous studies. Moreover, analyzing adaptive thermal comfort is another gap that was not addressed by preceding windcatcher studies, particularly for the tropical climate. Therefore, the current research aims to evaluate a two-sided windcatcher incorporated with the upper wing wall from two views: indoor air quality (IAQ) and adaptive thermal comfort. A small-scale model was tested in the wind tunnel. Next, CFD models were validated against experimental data with a good agreement between the two methods. Windcatchers with different upper wing wall lengths ranging between 10 cm and 50 cm were assessed. The results showed that the length increase led to a slight increase in the ventilation rate, and the best performance was seen in the 50 cm configuration. Subsequently, IAQ and adaptive thermal comfort were evaluated at different wind speeds of this climate. The results demonstrated that even in wind speeds below the annual average (2.5 m/s), the windcatcher performance can still satisfy IAQ parameters such as airflow rate and air change rate, recommend by CIBSE Guide A. In addition, based on the simulated conditions the results showed that wind speed from 2.5 m/s to 4 m/s could provide thermal comfort within 50%-80% of the ventilated space. Finally, the estimation of passive cooling power showed that windcatcher could provide a maximum (9.6 kW) cooling power if the wind speed is at 4 m/s and outdoor temperature at 23 °C.