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Re: [TRNSYS-users] Adiabatic wall
Maurizio,
This was discussed recently on this list.
As noted by Xavier Casals, a "boundary = identical" wall will have the
same AIR temperature on both sides. So the adiabatic plane is somewhere
inside the wall, not at the "outside" (or "back") surface. In other
words, the wall does not contribute to heat losses but it does
contribute to the thermal inertia.
Matthias Rudolph mentioned a solution if you need an adiabatic surface
at the "back" side of the wall:
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For boundary walls you can define a very small convective heat transfer
condition > 0.001 W/m²K. For alpha < 0.001 you will receive direct
contact (almost equivalent to > 999 W/m²K). We kept this for backwards
compatibility.
So if you want to create a wall with mass towards the zone and the
adiabatic condition on the back (not in the middle of the wall as in
boundary identical mode), you might use following approaches
1. choose a low alpha e.g. 0.002 on the back of the boundary identical wall
2. define the wall adjacent to a ficitve zone with alpha_back = 999. In
this fictive zone define a resistance only wall with alpha_front = 999
and boundary identical to the back.
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Also, you should remember that the building model in Type 56 is
non-geometrical. If you need a surface that does not exchange heat with
the zone, just skip it! Compared to the solution here above it does have
one drawback: the solar radiation distribution will be different (beam
is distributed according to GEOSURF, so you can fix it, but diffuse is
distributed according to absorptance weighted area ratios so it will be
different if you "forget" a large surface in your room). Long-wave
radiation will also be different since view factors are also
approximated by area ratios. But depending on what you really want to
simulate, just skipping a wall can be the solution.
Kind regards,
Michaël Kummert
--
_________________________________________________________
Michaël Kummert
Solar Energy Laboratory - University of Wisconsin-Madison
1303 Engr Res Bldg, 1500 Engineering Drive
Madison, WI 53706
Tel: +1 (608) 263-1589
Fax: +1 (608) 262-8464
E-mail: kummert@engr.wisc.edu
SEL Web Site: http://sel.me.wisc.edu
TRNSYS Web Site: http://sel.me.wisc.edu/trnsys