[Bldg-sim] "Qualified" energy modeling tools for LEED NC v2.2

[David Bradley]

Chaoqin,
  There are three parts to the geometry issue.

  For internal radiation exchange, you are correct that TRNSYS is a
non-geometrical model and that two surfaces do not have any knowledge of
their mutual view factor. Like many of the other building models out
there, TRNSYS uses a star-network in which each surface "radiates" to
the air node and vice versa.

  For external geometry, one defines orientations in the building
processor (TRNBuild) and then defines corresponding surfaces (slope and
azimuth) in the weather data reader. Solar radiation from a particular
weather data reader surface is then linked to the appropriate Type56
inputs for each orientation defined in TRNBuild.

  For external shading (including building self-shading), one places a
series of wingwall and overhang components between the unshaded solar
radiation calculated by the weather data reader and the building, in
effect cutting down on the amount of radiation incident on the building.
It is a flexible methodology but a bit of a cumbersome one. One of the
main pushes in the current development of TRNSYS 17 is a much more
automated methodology for doing building self-shading. The Type56
developers are also working on a true view-factor methodology for
internal radiation exchange within a zone.

Kind regards,
 David

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David BRADLEY - Principal
Thermal Energy System Specialists, LLC
2916 Marketplace Drive - suite 104
Madison, WI  53719
USA

Ph: +1.608.274.2577
Fx: +1.608.278.1475
bradley at tess-inc.com
http://www.tess-inc.com
http://www.trnsys.com
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