[TRNSYS-users] wall transmittance

[David BRADLEY]

Francesca,
   There are numerous ways of modeling walls both within TRNSYS and 
beyond the components that TRNSYS offers. I think it would be worth 
informing yourself about those modeling methods so that you can apply 
your data to the most appropriate of them. The simplest wall model 
accounts only for the wall's thermal resistance and discounts the wall's 
ability to store energy. It would be relatively easy to use simple 
equations to tune such a wall model's transmittance (thermal resistance) 
to match your data. You would not even need a Type. I don't think you'd 
get a very good fit for your data, however, because walls do have 
thermal mass.
   You could use a generic lumped capacitance model such as Type963 in 
the TESS Loads and Structures library in order to account for the 
thermal mass of the wall as well as its transmittance. However, with 
such a model you would be discounting where in the wall the mass is 
located (i.e. the fact that most walls are made up of different layers 
whose material properties can differ significantly from one to the next.
   Type56 uses a conduction transfer function coefficient wall model. 
Applying your data to such a wall model and backing out the CTF 
coefficients would be an interesting and non trivial research project in 
itself.
   Beyond the CTF wall model there are also finite difference wall 
models and I am sure others of which I am unaware.
regards,
  David


On 4/21/2015 4:33 AM, Francesca Pagliaro wrote:
> Thank you Jing for your answer. I'm actually trying to solve an 
> unsteady calculation and compare the results with experimental data, 
> therefore I'd prefer a type where the equation is already inside.
>
> 2015-04-20 21:59 GMT+02:00 Jing Hong <hongjing.shirley at gmail.com 
> <mailto:hongjing.shirley at gmail.com>>:
>
>     Francesca,
>
>     If you are just going to make a simple calculation, you may try
>     TYPE 9 as data input, insert equation for calculation and add a
>     printer to get output.
>
>     Jing
>
>     On Mon, Apr 20, 2015 at 9:33 AM, Francesca Pagliaro
>     <francesca.pagl at gmail.com <mailto:francesca.pagl at gmail.com>> wrote:
>
>         Hello Trnsys users, I’m trying to solve an inverse problem
>         related to wall transmittance. Is it possible to calculate the
>         transmittance of a wall setting in Trnsys only the external
>          and internal input such as heat flux, temperature, area, on
>         the two sides of the wall? If yes, how?
>
>         Thanks
>
>
>         Best regards
>
>
>         Francesca
>
>
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>     -- 
>     Doctoral Student
>     University of Wisconsin-Milwaukee
>     School of Architecture and Urban Planning
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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 at tess-inc.com

http://www.tess-inc.com
http://www.trnsys.com

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