Effects of inlet area on performance of a solar chimney for natural ventilation and heating of buildings

Abstract

Natural ventilation, one of the key elements of green buildings, can be achieved with solar chimneys. This device based on buoyancy effects induced by solar radiation to create air flow for ventilation. Among the factors influencing performance of a solar chimney is the area of the inlet. In this study, effects of reducing the inlet area on the performance of a vertical solar chimney was examined numerically. A CFD (Computational Fluid Dynamics) model was built on the ANSYS Fluent CFD code to simulate the air flow and heat transfer inside the solar chimney at different heights and gaps. The results showed that, as the inlet area decreases, the flow rate is almost unchanged until a critical ratio of the inlet area and the gap of the air channel. As the inlet area decreases further, the flow rate decreases at a constant rate. The temperature rise is always enhanced as the inlet area decreases. The changes of the thermal efficiency depend on the gap – to -height ratio. These observations can serve as references for design of air damper at inlet of solar chimney for a specific application, such as ventilation where higher flow rate is desired, or heating where higher temperature rise is preferred.