Experimental investigation on air heating and natural ventilation of a solar air collector

Solar air collectors are important components for solar energy utilization in green houses. In this paper, experimental studies were carried out regarding to a solar air collector (SAC), for which the length of air channel is 1500 mm, the width is 500 mm, and a variable air channel gap ranges from 100 to 500 mm. In the experiment, the uniform heat flux along the air channel is effected by three electric heating plates, which play a role as solar radiation. It is found that the temperature distribution of air and the induced natural air-flow rate are highly dependent on heat input, inclination angle, channel gap, etc. Experimental results indicate that the optimum inclination angle for the SAC is 45°, under which a maximum natural ventilation rate can be created. Also found is that there exists an appropriate channel length, about 1 m in this study, beyond which the obtained heat and the natural ventilation rate cannot be increased drastically. Higher the volume of air-flow rate through the SAC, lower the temperature difference between inlet and outlet, consequently, it should be balanced between the air temperature rise and a suitable mechanical air-flow rate in order to obtain maximum heat. Additionally, theoretical analysis based on heat balance equations is testified to agree well with experimental results.