NUMERICAL ANALYSIS OF SOLAR CHIMNEYS FOR VENTILATION IN BUILDING

Abstract

The ventilation of buildings is essential to improve the air quality indoors and thermal comfort. Mechanical ventilation systems are now most often used in buildings, such as air conditioning and ventilation. This equipment however consumes a lot of electricity, generated mainly by fossil fuels, which lead to greenhouse gas releases and thus to climate change. As such, it is important to switch to environmentally friendly natural ventilation systems based on renewable energy sources. The solar chimney, which can be mounted or walled up into buildings, is such a natural ventilation system. This study aimed to develop a mathematical model that evaluates the thermal performance of solar chimneys mounted in inclined or wall mounted. The model has been validated with CFD digital simulations. In order to compare their results with regard to the ventilation rate expresses as the number of air changes per hour, ACH, CFD designed and model various configurations of solar chimneys. For, Jodhpur, India, crude climate information was obtained, including global and diffuse solar radiation intensities on a horizontal plane, wind speed and ambient temperature. This was used in the modelling of solar chimneys by CFD. The effect on the thermal performance of solar chimneys from inclination angle, air gap, and chimney height and view factor was examined in the current study. The results show good agreement between modelled data from this research and literature-reported experimental values. The root mean square errors were respectively 13 & 20 % for models with and without the view factor. Moreover, a tilting angle of 60° was found to be the optimal tilting angle for as this angle achieved the maximum ventilation rate. Furthermore, the ventilation rate increased, with the air gap increased. When the chimney height was increased, a rise in ACH was observed. It was also noted that when designed to achieve more realistic ventilation rate values, the view factor was an important parameter to be seen. Additionally, ACH has been increased by the inclusion of the view factor. Overall, sloping solar chimneys with a roof give higher thermal performance than vertical solar chimneys mounted on a wall. Furthermore, the inclusion of the viewing factor increases the precision of the modelling of a solar chimney.