Mathematical analysis of the influence of the chimney height and collector area on the performance of a roof top solar chimney

Determination of the roof top solar chimney behaviour during the day time is essential for the proper designing and sizing. This paper presents a mathematical model and analysis of an inclined type roof top solar chimney. The thermal energy and fluid flow processes were simulated mathematically based on the energy and mass balances. The model was converted to a MATLAB computer program and solved by iteration method. The analysis was carried out at various collector areas (15, 150, and 600 m2) and various chimney heights (5, 10, and 15 m). The model was validated by comparing the results with the experimental measurements. The developed mathematical model was able to predict the dynamic behaviour of the system. The results demonstrated that the performance of the system is highly influenced by the solar intensity. The system becomes functional for space ventilation when the solar intensity is higher than 400 W/m2 with a 15 m2 collector area and 5 m chimney height, under Malaysia and similar weather conditions. As the wind speed increases from 1.5 to 6 m/s, it contributes to reduce the system performance by 25% at solar intensity of 900 W/m2.