[TRNSYS-users] Window with shading

[Jong, M.J.M.]

Christian, Michael and other TRNSYS users,

A few months ago I had a similar problem. What I did at that time was the
same as the third option that Michael suggested. What I first did was to run
a simulation with double glazing without the internal shading device. After
that I added an additional zone (with 2 single glazed windows) that
represented the air gap of the double glazing. I compared the results of
both simulations (annual heating demand) with eachother and there was a
difference. I adjusted the convected heat transfer coefficient of both
single glazed windows (on the "air gap side") just as long as I had the same
annual heating demand compared to the simulation with double glazing. In my
case both heat transfer coefficients were 0.3 kJ/hr m2 K. After that you can
add an internal shading factor (with an input) to the single glazed window
that borders on outside. It is a bit difficult to say if this represents
reality well, but I used it one time in my simulations and the results
seemed (and I want to stress seemed) to be OK.

There is maybe a better solution, but this is something that I did not know
at that time. With the window software you can configure 2 different
windows. One window represents the double window with the internal shading
down and the other window represents the window with the internal shading
device up. In Prebid, you can define the window ID number as an input and
depending the weather and indoor conditions you can switch the window in
your *.dck file. I have no experience with this and I do not know if it is
easy for you to define the 2 windows (internal shading up and down) with the
Window software, but I can imagine that it works well.

I hope this helps and as Michael already wrote, comments or other
suggestions are very welcome.

Regards,

Maurice Jong
ECN-DEGO
The Netherlands



-----Original Message-----
From: Michaël Kummert [mailto:kummert at engr.wisc.edu]
Sent: 13 July 2004 18:16
To: trnsys-users at engr.wisc.edu
Subject: Re: [TRNSYS-users] Window with shading


Christian,
> 
> i have to do an simulation of an multizone building with windows, which
> have an internal shading device between the inner and outer pane of the
> glazing.
> But i dont have any idea how to deal with that.
> I don't think that the opportunities that Prebid offers in order to create
> an internal
> or external shading are sufficent for that kind of window!
> The only idea i have is to use the programm window. But how can i
> define the internal shading device between the panes? What are the
> properties
> in this case?
> Does anyone have an idea? Thank you in advance!
> 

I don't think WINDOW (4 or 5) allows you to define shading devices.
My understanding is that the WIS program (www.windat.org) allows to 
model such configurations, but it is still under development and there 
is no standardized way of using its output in TRNSYS.

Here are a few other ideas on how you could approach the problem (Please 
take them for what they are worth, i.e. not more than 2 cents ;-)

- You could cheat on the absorptance of 2 panes to get the desired
   behavior in some "standard" steady-state conditions, but this requires
   a good knowledge of WINDOW and it is only an approximation.

- Find an upper and lower bound of the system's performance by placing
   the shading inside and outside (resp. minimum and maximum cooling load
   reduction)

- Use a fictitious zone with two single-glazed windows. This is probably
   not a very good idea, you would have to run many checks to make sure
   the thermal and optical behavior makes sense if you go for that
   solution...

I hope this helps (and I hope other TRNSYS users will comment on this),


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 at engr.wisc.edu

SEL Web Site: http://sel.me.wisc.edu
TRNSYS Web Site: http://sel.me.wisc.edu/trnsys
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