Re: [EnergyPlus_Support] Interior Shade

["Michael J. Witte" <mjwitte@xxxxxxxx>]

I am not sure what you mean by "then a geometric series used assuming 
infinitely long flat plates".  

Reference Figure 63 in the Engineering Reference (p. 146, pdf p. 177), and the 
equations under the subheading "Interior Shade" (p. 152, pdf p. 183).  

Based on my limited understanding, the overall transmittance of the unshaded 
glazing system (T1,N) is calculated first, both for the current angle of 
incidence and for diffuse radiation. 

Then the diffuse back reflectance of the unshaded glazing system is calculated 
(in the figure this is RbN,1, in the equation this is Rb,diff).  This is not 
angular-dependent, of course.  Only the diffuse back reflectance is required, 
because shades are assumed to be perfect diffusers for both reflectance and 
transmittance (see p. 151, pdf p. 182).

Then the equations in the "Interior Shade" section are applied using the 
overall glazing system transmittances (angular and diffuse) and back 
reflectance (diffuse) plus the shade reflectance (diffuse) and transmittance 
(diffuse) to determine the overall shaded glazing system properties.

Diffuse properties are computed as described under the subheading "Calculation 
of Hemispherical Values" (p. 150, pdf p. 181).

There does not appear to be any calculation of a component which may slip past 
the shade through the gap at the bottom of the window.  So, in that respect, 
the window is infinitely long.

Does this help?  Or have I missed the point of your question?

Mike



On 16 Mar 2006 at 13:14, Peter G Loutzenhiser wrote:

> Dear All,
> 
> When EnergyPlus simulates an interior shades for windows, is the 
> initial beam radiation component transmitted through the glazing 
> unit/window  angular dependent and then a geometric series used 
> assuming infinitely long flat plates.  The Engineering manual leads 
> me to believe that only diffuse solar transmittances and reflectances 
> are used to calculate the overall transmittance of the blind+glazing 
> unit/window , but I am unsure.
> 
> Regards,
> Peter
> 
> 
> 
> The primary EnergyPlus web site is found at:
> http://www.energyplus.gov
> 
> The group web site is:
> http://groups.yahoo.com/group/EnergyPlus_Support/
> 
> Attachments are not allowed -- please post any files to the appropriate folder
> in the Files area of the Support Web Site.
> 
> EnergyPlus Documentation is searchable.  Open EPlusMainMenu.idf and press the
> "search" button.
>  
> Yahoo! Groups Links
> 
> 
> 
>  
> 
> 
> 
> 


========================================================
Michael J. Witte, GARD Analytics, Inc.
EnergyPlus Testing and Support      
EnergyPlus-Support@xxxxxxxx





The primary EnergyPlus web site is found at:
http://www.energyplus.gov

The group web site is:
http://groups.yahoo.com/group/EnergyPlus_Support/

Attachments are not allowed -- please post any files to the appropriate folder in the Files area of the Support Web Site.

EnergyPlus Documentation is searchable.  Open EPlusMainMenu.idf and press the "search" button.
 
Yahoo! Groups Links

<*> To visit your group on the web, go to:
    http://groups.yahoo.com/group/EnergyPlus_Support/

<*> To unsubscribe from this group, send an email to:
    EnergyPlus_Support-unsubscribe@xxxxxxxxxxxxxxx

<*> Your use of Yahoo! Groups is subject to:
    http://docs.yahoo.com/info/terms/