Calculation of the Shape Factor From a Small Rectangular Plane to a Triangular Surface Perpendicular to the Rectangular Plane Without a Common Edge

In developing an analytical model of radiative heat transfer inside attics, the necessity of calculating the shape factor from a small rectangle to a triangular plane may arise. This paper describes a methodology of calculation for such a shape factor from simple relations using shape-factor algebra. The shape factor is calculated using a mirror image of the triangular surface, in such a way that the small rectangular plane is positioned symmetrical between the two triangular surfaces. Numerical results are presented in graphical form.