Zhe,
TRNBuild has two concepts that are important here. An "airnode" is
an area of the building that can be represented by a single air
temperature. A "radiation zone" is volume within the building in
which all of the walls can "see" each other. How you decide to break
up the building into airnodes and radiation zones depends on what is
crossing the boundaries between them. For example if you have an
atrium with a glass roof or a glass wall there is going to be
vertical stratification (i.e. multiple airnodes) and it is the solar
radiation that is going to cross the airnode boundaries so you'll
combine those airnodes into a single radiation zone. Virtual
surfaces are used as boundaries between the airnodes because
radiation can cross a virtual surface.
In your case, I think you have a greenhouse attached to the side
of a building so that there will certainly be a temperature
difference between the greenhouse and the rest of the building but
there probably won't be very much radiation crossing the boundary
between the two. In this case there isn't any need to define a
virtual surface because there isn't much radiation passing. You can
define there to be a "wall" between the two airnodes when you are
drawing the building in SketchUp. Then when you go to TRNBuild, you
can set that wall's properties so that it has a very low thermal
resistance (high u value). In this way the wall will allow you to
define convection between the two airnodes and there will be little
resistance to conduction heat transfer.
best,
David
On 07/20/2015 19:17, Zhe Kong wrote:
Hi everyone:
I just star learning Trnsys and come up with a basic
inquiry. Does anyone know how to create two airnodes within
one zone in sketchup before exporting into Trnsys? We
want to build a one-floor greenhouse mostly enclosed by
glazing. The sloped roofs are also in glazing. We want to do
the calculation concerning solar radiation and heat flow
without HVAC system.
Currently
we built two zones (the plant one and the air one) with the
mutual surface set as virtual surface; however, even the two
virtual surfaces disappeared when being exported into
Trnsys, the two zones seemed to have no air flow connection.
The results show that the plant zone has small range of
temperature change, while the air zone has a much larger
range. We realized we should build the sketchup model with
two airnodes and one zone, but we didn't figure out how to
do it. Another question is, in that case, is there anyway we
can set different inputs according to the two airnodes?
Thank you in advance.
--
Zhe
Kong
PhD
Student
University
of Wisconsin - Milwaukee
School
of Architecture and Urban Planning
2131 E.
Hartford Ave, Milwaukee, WI 53211
Office
327
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***************************
David BRADLEY
Principal
Thermal Energy Systems Specialists, LLC
22 North Carroll Street - suite 370
Madison, WI 53703 USA
P:+1.608.274.2577
F:+1.608.278.1475
d.bradley@tess-inc.com
http://www.tess-inc.com
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