Dear Benoit,<br><br>Thanks for your patient reply!<br>I saw your attached figure. But there is a new problem. As I said for my first email, my air layer is about 1m, however, this figure's maximal thickness of air is only 300 mm. therefore, Whether or not it is right when I still use 4.5 W/m2K your figure said as the air layer's U-value?<br>
<br>thanks!<br>Br.<br><br>yang wang<br><br><div class="gmail_quote">2012/11/21 Benoit Delcroix <span dir="ltr"><<a href="mailto:benoit.delcroix@polymtl.ca" target="_blank">benoit.delcroix@polymtl.ca</a>></span><br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
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<div>Hi, <br>
<br>
The new value is including convection, radiation and conduction
(and not only conduction). There is a reference in English in 2009
ASHRAE Handbook - fundamentals (chapter 26). The reference I have
is in French (a Belgian regulation on energy performance of
buildings). I have attached a jpg file with the table if you want.
The first column is the thickness (in mm). The 3 next are
depending on the heat flux direction (respectively upward,
horizontal and downward). And the values in the table are
resistances in m²K/W. The reference in ASHRAE is a little bit more
complicated. <br>
<br>
Best,<br>
<br>
Benoit<br>
<br>
Le 2012-11-21 04:27, 王洋 a écrit :<br>
</div><div><div class="h5">
<blockquote type="cite">Dear Benoit,<br>
<br>
Thanks for your reply!<br>
<br>
I did as you said, i.e. I changed the air U-value from 0.09252
W/m2K into 4.65 W/m2K. Then the min. timebase 2 hours can work.
But I'd like to ask you why we should set this value 4.65 W/m2K?
Could you please tell me which reference literature said? Because
I checked the air conductivity as 0.09252 kJ/hmK from the
literature.<br>
<br>
Thanks!<br>
Br.<br>
yang wang<br>
<br>
<div class="gmail_quote">2012/11/20 Benoit Delcroix <span dir="ltr"><<a href="mailto:benoit.delcroix@polymtl.ca" target="_blank">benoit.delcroix@polymtl.ca</a>></span><br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
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<div>Hello,<br>
<br>
To me, I think you should set your air layer as a
resistive layer and set the air U-value to 4.55 - 4.65
W/(m²K) (if there is no ventilation in the basement). And
normally, afterwards, you should be able to decrease the
timebase value (normally 1 hour should be possible). If
you want less, split the heaviest walls with an active
layer (probably the roof and groundfloor walls).<br>
<br>
Best,<br>
<br>
Benoit <br>
<br>
Le 2012-11-19 04:31, 王洋 a écrit :<br>
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<blockquote type="cite"><br>
Dear Leen, Jean, Marion, Benoit and others,<br>
<br>
Many thanks for your reply!<br>
<br>
I checked my Wall's thickness and thermal property
etc. again. Why needs it 9 hours as the timebase? I
think maybe it is due to my Ground floor (it is the
basement's floor of the building) which includes about
0.99 m's Air Layer.<br>
When I changed it into 0.1 m, the min. timebase 2.5
hours can work without the ERROR:Error creating the
wall transfer function coeffients.<br>
<br>
Therefore, I'd like to ask you, <br>
1) Is it normal for TRNBuild setting how large the
timebase is maximally? 5 hours or others?<br>
2) How to solve this problem of the ground floor with
about 0.99 m's Air Layer? But our building project
indeed has<br>
the ground floor with about 0.99 m's Air Layer. I
can't reduce it into 0.1m? Is the only way to <span style="color:rgb(51,51,255)"> try the active layer
approach of The group of Michael Kummert in Montreal</span>?
<br>
<br>
Please see the Attached INF file.<br>
<br>
Thanks in advance!<br>
Br.<br>
<br>
wang<br>
<br>
<br>
<div class="gmail_quote">2012/11/17 Benoit Delcroix <span dir="ltr"><<a href="mailto:benoit.delcroix@polymtl.ca" target="_blank">benoit.delcroix@polymtl.ca</a>></span><br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
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<div>Hello,<br>
<br>
I'm one of the students of Michaël Kummert
working on a new method to generate the
tranfer functions. I thing I can help you for
your problem. As Leen said, TRNSYS is unable
to generate the transfer functions
coefficients for a heavy and insulated wall
with a low timebase. In the TRNBuild project,
you can modify that value and increase it to
allow TRNSYS to generate the transfer
functions. Actually, TRNSYS is unable to
generate the transfer function as soon as the
Fourier number of the wall (thermal
diffusivity * timebase / thhickness²) is lower
than 0.0005. To check that, TRNBuild make the
sum of one of the coefficients series (a, b or
c). The 3 sums are equal and means, according
to TRNBuild (I don't personally think so...but
it's like this), the Fourier number. <br>
<br>
As Leen said, it exists a trick. You can use
an active layer to split the wall in 2 and
then forcing TRNSYS to generate 2 series of
transfer functions coefficients for the same
wall. As the 2 parts are thinner, you could
use a better timebase value. When you insert
the active layer in the wall, try to split the
layer with the lowest Fourier number. And then
to insert the active layer, use the expert
mode that allows you to insert an equivalent
conductivity. Insert the biggest value you
can. Like that, the active layer is negligible
at the thermal point of view. Actually, the
active layer is acting as a mini-zone to split
the wall. It is a little tricky but it
works...before having better solution.<br>
<br>
Good luck for your project and have a nice
week-end,<br>
<br>
Benoit <br>
<br>
Le 2012-11-17 14:43, <a href="mailto:trnsys-users-request@cae.wisc.edu" target="_blank">trnsys-users-request@cae.wisc.edu</a>
a écrit :<br>
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