[TRNSYS-users] Fwd: Error creating the wall transfer function coeffients

Fri Nov 23 01:32:56 PST 2012

Thanks!

But I checked 2009 ASHRAE Handbook - fundamentals (chapter 26.3), it
said interpolation
and moderate extrapolation for air spaces greater than 90 mm are also
permissible.

Therefore, I think we can also set all those almost still air cavity with 1
m thickness as one layer of ground floor in the basement.

Br.

yang wang

2012/11/23 Jean Marais <jeannieboef at gmail.com>

> Ideally, yes.
>
>
> On 23 November 2012 09:48, 王洋 <wanghongyang1767 at gmail.com> wrote:
>
>> Dear Marion,
>>
>> Thanks for your email!
>>
>> But all those air cavity with 1 m thickness is not connected together.
>> They are separated into 11 parts due to 11 zones in the basement.
>> Do you mean like this situation all those air cavity still should be
>> modelled by a zone?
>>
>> Thanks!
>> Br.
>> yang wang
>>
>>
>> 2012/11/23 Marion Hiller <hiller at transsolar.com>
>>
>>> ** ** **
>>>
>>> Wang,****
>>>
>>> ** **
>>>
>>> a cavity of 1m should definitely be modelled by a zone! ****
>>>
>>> The “edge” effects shouldn’t be neglected.****
>>>
>>> ** **
>>>
>>> ** **
>>>
>>> ****Marion********
>>>
>>> ** **
>>>
>>> ** **
>>>
>>> *Dipl.-Ing. Marion Hiller **
>>> **TRANSSOLAR: KlimaEngineering - Technologien für energieeffizientes
>>> Bauen und Nutzerkomfort in Gebäude **
>>> Munich - New York - Stuttgart + 49.711.67976.0
>>>
>>> **Transsolar Energietechnik GmbH, Curiestrasse 2, 70563 Stuttgart
>>> Amtsgericht Stuttgart - HRB 23347, Steuernummer 99073/00911, USt-IdNr.:
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>>> Dipl.Phys. Stefan Holst, Prof. Dipl.-Ing. Bleicher *
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>>>  ****
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>>> ** **
>>>  ------------------------------
>>>
>>>
>>> *Von:* 王洋 [mailto:wanghongyang1767 at gmail.com]
>>> *Gesendet:* Donnerstag, 22. November 2012 16:25
>>> *An:* **Benoit Delcroix**; **trnsys-users**
>>> *Betreff:* Re: [TRNSYS-users] Fwd: Error creating the wall transfer
>>> function coeffients****
>>>
>>> ** **
>>>
>>> Dear Benoit,
>>>
>>> Thanks for your patient reply!
>>> 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?
>>>
>>> thanks!
>>> Br.
>>>
>>> yang wang****
>>>
>>> 2012/11/21 **Benoit Delcroix** <benoit.delcroix at polymtl.ca>****
>>>
>>> Hi,
>>>
>>> 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.
>>>
>>> Best,
>>>
>>> Benoit
>>>
>>> Le 2012-11-21 04:27, 王洋 a écrit :****
>>>
>>> Dear Benoit,
>>>
>>> Thanks for your reply!
>>>
>>> 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.
>>>
>>> Thanks!
>>> Br.
>>> yang wang****
>>>
>>> 2012/11/20 **Benoit Delcroix** <benoit.delcroix at polymtl.ca>****
>>>
>>> Hello,
>>>
>>> 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).
>>>
>>> Best,
>>>
>>> Benoit
>>>
>>> Le 2012-11-19 04:31, 王洋 a écrit :****
>>>
>>>
>>> Dear Leen, Jean, Marion, Benoit and others,
>>>
>>> Many thanks for your reply!
>>>
>>> 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.
>>> 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.
>>>
>>> Therefore, I'd like to ask you,
>>> 1) Is it normal for TRNBuild setting how large the timebase is
>>> maximally? 5 hours or others?
>>> 2) How to solve this problem of the ground floor with about 0.99 m's Air
>>> Layer? But our building project indeed has
>>> the ground floor with about 0.99 m's Air Layer. I can't reduce it into
>>> 0.1m? Is the only way to  try the active layer approach of The group of
>>> Michael Kummert in Montreal?
>>>
>>> Please see the Attached INF file.
>>>
>>> Thanks in advance!
>>> Br.
>>>
>>> wang
>>>
>>> ****
>>>
>>> 2012/11/17 **Benoit Delcroix** <benoit.delcroix at polymtl.ca>****
>>>
>>> Hello,
>>>
>>> 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.
>>>
>>> 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.
>>>
>>> Good luck for your project and have a nice week-end,
>>>
>>> Benoit
>>>
>>> Le 2012-11-17 14:43, trnsys-users-request at cae.wisc.edu a écrit :****
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