Developing an empirical model for roof solar chimney based on experimental data from various test rigs

Abstract

Roof solar chimney is one type of solar chimney to enhance the natural ventilation in buildings. Under the factor that previous studies numerically modelled and validated their results by single test rig, experimental data from all the possible test rigs in the literature were collected and analysed in this study to develop an empirical model for general use. This empirical model was validated by experimental data from various test rigs, with an average error of 14% and up to 144.6% error. Based on the experimental data from different test rigs, the influences of several factors, such as calculated inclination angle (θ′, shown in Eq. (6)), cavity gap (d), width (w), height (H), height/cavity gap ratio (H/d), inlet area (Ain), outlet area (Aout) and radiation heat (q), on solar chimney performance were addressed. The volumetric flow rate of roof solar chimney showed a linear relationship with w(sinθ′)1/3q1/2d0.7H2/3. The slope of this linear relationship can be determined by test environment, cavity material, glazing, and insulation conditions. Those experimental data within a H/d range of 2.5–103.5 showed that the air velocity increases with a larger H/d, but the volumetric flow rate behaves in an opposite way. It is known from experiments that an equal inlet and outlet area can enhance the flow rate in the cavity and for unequal openings the outlet area showed a relatively higher importance in promoting the air flow.