CFD modelling of transient thermal performance of solar chimney used for passive ventilation in a building

Abstract

The paper analysed the 24 hour performance of a solar chimney placed on a building roof in Krakow, Poland. The solar chimney was an element of as a passive ventilation system allowing energy efficient night ventilation during the summer season. The chimney was built as an air duct. Three walls of the chimney were made of glass and faced toward the sun, the opposite wall was made of a concrete absorber. The system worked in two stages: day and night. The absorber located in the chimney was heated during the day, and cooled during the night. During the night phase, the released heat provided a draft contributing to passive ventilation.Absorbers with different thermal capacities were studied. Simulations were conducted for three different absorber thickness 10 cm, 20 cm or 30 cm. The simulations were carried out using the Ansys Fluent simulation software. The hourly results of temperature distributions in the chimney allowed the authors to determine the optimal absorber thickness for the passive ventilation system. Calculations showed that the chimney with the absorber that was 10 cm thick was the optimal among analysed solutions. The absorber is warmed up to the highest temperature, up to 82°C, and induces air flow which lets removing even 3820 m3 of air during the night.