Abstract
A solar air heater with a built-in net was proposed and the collection characteristics were experimentally investigated. Eight kinds of metallic nets, which had different transmissivity and opening fraction, were configured parallel in the space between the transparent cover plate and absorber. The temperature distribution within the air layer and pressure drop were measured, and the effects of the net transmissivity and opening fraction on the temperature distribution, collection efficiency and pressure drop were examined.
When the metallic net was inserted in the solar air heater, the temperature distribution within the air layer was quite different and the collection efficiency became 16 to 35% higher than those of conventional solar air heaters and solar air heaters without a net. The collection efficiency had a maximum against the net transmissivity. By changing the net setting position, the pattern of temperature distribution was much affected while the collection efficiency was hardly affected. The pressure drop in the present solar air heater was higher than those in the conventional solar air heater and the solar air heater without a net, and had a maximum against the net transmissivity, i.e. the net opening fraction.
