Abstract

Natural ventilation driven by a solar chimney attached to a single-room building was studied experimentally using a small-scale model. The experiments were performed using a recently developed fine-bubble technique in which fine hydrogen bubbles are produced electrolytically in salt solution to simulate the buoyancy effect in the chimney caused by temperature differences. During the experiments, one sidewall of the solar chimney was uniformly "heated", corresponding to a uniformly distributed solar radiation incidence. Velocities at the room inlet were measured by a particle tracking method; in turn, the average flow rate through the solar chimney system was determined. Parameters studied in the experiments were the cavity width of the solar chimney, the solar radiation intensity, the ventilation inlet areas, and the solar chimney height. Results showed that for a given building geometry and inlet areas, there is an optimum cavity width at which maximum ventilation flow rate can be achieved. This optimum cavity width, which is independent of the solar radiation intensity, was found to be dependent on the size of the ventilation inlet areas and the solar chimney height. Observations were made on the flow patterns within both the solar chimney and the room. Two simple theoretical models were developed, based on common tools found in literature used for solar chimney ventilation prediction. Comparison between the measured ventilation flow rates and the theoretical predictions indicated that theoretical models, based on simplified temperature assumptions within the chimney, may over-predict the solar chimney ventilation performance and should be used with care.