Experimental study of the chimney effect in a solar hybrid double wall

The solar hybrid-wall is widely used in natural ventilation and air heating in buildings. This article aims to experimentally study the induced chimney effect in a solar hybrid double wall. The effect of the air ventilation gap width and solar radiation intensity on the temperature distribution and induced air flow rate at the outlet of the hybrid wall was investigated with a variable chimney gap width-to-height ratio between 1:10 and 3:5. The results demonstrated that a lowest temperature position exists in the air gap and the position varies with the width of the air gap. The average air velocity in the air gap increases with the strength of the radiation intensity, and it shows a peak value with decreasing chimney gap width. The induced mass flow rate increases with both the radiation intensity and the chimney gap width. The optimum chimney gap width-to-height ratio is around 0.2–0.3 according to the coupling effect of the temperature and the air volume. Smoke visualization experiment demonstrates that reverse flow occurs in solar chimneys with a gap width-to-height ratio bigger than 0.3. It was found that the prediction method available in the literature can be well applied to narrow chimneys with a gap width-to-height ratio less than 0.3.