Re: [EnergyPlus_Support] Re: glare index difference (upload the input files)

On Thu, Nov 5, 2009 at 6:36 PM, YuanLu Li <yli006@xxxxxxxxxxx> wrote:

Hi, Jia,

I have another suggestion which may help to make the results easier to compare. The model used in the EPlus examplefiles folder has two zones.

If you expand your building to, say, four zones side by side, you can then have one window without blind, one with horizontal, one with vertical, and/or for dividing the window glass into smaller sections.

Turn on the display of the Output:IlluminanceMap. You can then see the intensity in the whole room for each zone.
=================
The following are related to your IDF.

Do not forget that you have a schedule for the lighting, the Sunday result will be different from the other days.

You have chosen FixedSlatAngle in the  WindowProperty: ShadingControl. The slat angle of the blind does not change, when the glare index is larger than 22.

Glare Calculation Azimuth Angle of View = 90 or 270 faces an opaque wall. The illumination on ref. point 2 is low and therefore gave you zero glare index. The blind angle of 45 degree blocked the solar beam as well.

I have not run the annual simulation with your IDF, and have ran only one designDay each for the 0.4% Winter and 99.6% Summer, with the intermediate DesignDay object removed.

If you are only interested in the Daylighting, the HVAC section need not be installed for all zones.

Dr. Li

To: hujia06@xxxxxxxxx; EnergyPlus_Support@xxxxxxxxxxxxxxx
From: thong@xxxxxxx
Date: Thu, 5 Nov 2009 14:10:05 -0800
Subject: [EnergyPlus_Support] Re: glare index difference (upload the input files)

Hi Jia,

EnergyPlus calculates glare index by dividing the window into Nx by Ny rectangular elements and integrating the results. Look at the Daylight Discomfort Glare section of the Engineering Manual for description of the calculation procedures. By splitting a large window into small pieces, I expect to see different glare index calculated. To further identify the potential issues, you can make a few more parametric runs by splitting the large window into 2, 5, and 10 small ones, then look at the glare results to see any pattern.

Tianzhen

On 10/28/2009 12:03 PM, Hu,Jia wrote:

Dear all,

I have a question about Glare Index..

First, I simulate an office with a single big window. The width and the height of the window are 1.8m*1.8, There are interior blinds for this window, the angle is 45 deg. Through simulation, I got a glare index in every hour.

Then, I divided the big window into 3 small windows (each is 1.8 (width)*0.6(height) ) by defining three objects (all of them are windows) in FenestrationSurface:Details. And each small window has the same binds angle and width as the above one.

The problem is that when I ran the two simulations, I found the some differences of glare index in these simulations (only the number of window is different, the total area of the window and all each condition are the same) is nearly 10%. I am confused with this phenomenon.

I also uploaded the two input files and the EXCEL showing the differences to yahoo group at File : /_Problem_Submittals/glare index comparison.zip. You can also download it at URL:

http://groups.yahoo.com/group/EnergyPlus_Support/files/_Problem_Submittals/glare%20index%20comparison.zip

Could anyone explain the reason why the glare index is difference even if the two input files are the same except the number of windows?

Thank you.

Jia

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