NET THERMAL-RADIATION UNDER SHADING SCREENS

A model for the prediction of nocturnal net thermal radiation, under a woven shading screen, stretched horizontally above the ground or forming a tunnel, is developed. A radiation transfer factor is defined and calculated for the cases of a triangular cross-section shading tunnel made of a woven screen and of a hemicylindrical shading tunnel. Radiation is assumed to be diffusely emitted, transmitted and reflected by all surfaces. The model suggests that three parameters affect net radiation under the screen, namely, screen solidity, radiometric properties of the screen and the ratio between screen area and the ground area beneath it. The model is verified by experiments with aluminized and black polyethylene screens. The net radiation under the aluminized screens is lower than under the black ones.