An EXTERNAL floor means that there are ambient conditions on the back side of the floor of your zone. With an EXTERNAL surface, you'll need to provide an orientation so that TRNSYS can determine how much solar is incident on the back (outside the zone) surface. Type56 will also assume that the temperature and RH of the air on the back side of the surface are the ambient temperature and RH provided to the model. Bear in mind that there is no inherent meaning to "GROUND_FLOOR." That is just a name assigned to a construction.
There are certainly buildings in which all or part of the bottom floor is above some ambient conditions (perhaps there is an open parking garage underneath or perhaps part of the building is cantilevered. For this type of floor, you'd set the "view factor to sky" to 0 because the back surface of the floor faces the ground and doesn't "see" the sky for longwave radiation exchange. Geosurf asks for the fraction of the beam solar radiation that makes it into the zone that strikes the floor. If your zone is large with relatively few windows you can set that value to 1 thereby assuming that all the beam radiation causes sun patches on the floor. The surface gains on the inside and outside surfaces should probably be set to zero. They are a simplified way of modeling radiant surfaces.
As a side note and if you have not done so already, it might be a
good idea to consult the Type56/TRNBuild documentation, which
defines all of the fields that TRNBuild asks the user to fill in.
kind regards,
David
Deal all,
When I set 1st gournd floor as external catagory, what should I set these parameters ？
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-- *************************** David BRADLEY Principal Thermal Energy System Specialists, LLC 3 North Pinckney Street - suite 202 Madison, WI 53703 USA P:+1.608.274.2577 d.bradley@tess-inc.com http://www.tess-inc.com http://www.trnsys.com