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[EnergyPlus_Support] Calculation of angular properties


   I have some doubts about the calculation of angular properties for uncoated
glass. This section is part of the engineering document and since I'm using an
previous version of EnergyPlus (1.1.1.012), I will describe the equations and
show its numbers used in my manual version. The "Calculation of Angular
Properties" sub-section is located in the EngineeringDoc.pdf, chapter
"Daylighting and Window Calculations", section "Window Calculation Module".

   In this sub-section, on "Angular Properties of Uncoated Glass" description,
the first two equations (1.87 and 1.88) relates the angular function of
transmittance and reflectance ("T" and "R") with the angular function of
transmissivity and reflectivity ("tau" and "ro"). I have two questions:

1 - The "phi" angle is the incidence angle, but it is not clear what angle is
the "phi'"? It is the refraction angle inside the glass?

2 - I concluded that terms with the -ivity ending (transmissivity,
reflectivity) are refered as material properties (no matter physical features),
while terms with the ?ance ending (transmittance, reflectance) are refered to
samples because in these equations are functions of thickness. This is correct?

   Finally, in equation 1.90, that gives the spectral transmissivity as
function of the spectral reflectivity: tau(phi) = 1 - ro(phi), the third doubt
is:

3 - Where is the spectral absorptivity term "alpha(phi)"?


________________________________________________________
 Engº Fábyo Luiz Pereira
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 Fone / Fax: +55 51 3316-3167 / 3316-3355
 www.mecanica.ufrgs.br/lafrig
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