[TRNSYS-users] problem of windows and layers definitions

[David BRADLEY]

Pauline,

On 5/16/2012 09:38, Pauline GELIN wrote:
>
> Hello,
>
> I am so sorry to insistbut, despite several tests, I can not find the 
> answers to my questions from the previous mail. Does anyone even just 
> have an idea of quick answer ?
>
> Ialso appeal to you about another problem I have with each project on 
> TRNSYS.
>
> WhenI define a set temperature at a specific time (eg 20 ° C at 7am), 
> the temperature zones does not reach 20 ° C at 7am but an hour later.
>
> It seems that, at 7 am, the temperature israther than the average 
> value between the past temperature and the set temperature.
>
The answer depends a bit on how you are defining your set temperatures 
(whether you are using a SCHEDULE in Type56/TRNBuild, whether you are 
using an equation, whether you are using a thermostat component such as 
Type108, whether your building is in energy rate control or temperature 
level control). If you can give me some more information about how you 
are setting your temperature, I can give you a more specific answer.

A couple other things to keep in mind: 1) The online plotter shows 
linear interpolations between points because it only plots one point per 
timestep. If you are running with a 1 hour timestep and the temperature 
is 18 at 6AM and 20 at 7AM, you will see a line connecting these two 
points, even if there was a setpoint change at 7AM. If you hold down 
both the CTRL and SHIFT keys while looking at the online plot, you will 
see the actual (not the interpolated) values of your variables appear 
and you will see that while the plotter shows a linear increase from one 
point to the next, in fact it went through a step change. 2) TRNSYS's 
outputs /are /in fact the average values over a timestep so what you are 
seeing may indeed be correct.
>
> Do we have to clarify something (a field) about the component type 
> 9,used to read the text file with the set temperatures for each hour 
> of the year ?
>
I am not sure what you mean by this. Type9 reads the text file and you 
need to tell it (for each column that it reads) whether the value it is 
reading is an average over the data interval or an instantaneous value 
at the end of the data interval. You also need to specify whether the 
Type9 should be interpolated or not if your simulation time step is 
shorter than your data interval.
>
> Another issue related to the last, I created a schedule where the 
> value, I want to have between six and seven am, is written at 7 
> am,according to the documents I thought TRNSYS read the value for the 
> before hour. Is this true?
>
In order to interpolate properly, Type9 keeps track of the time at which 
the last read occurred and the time at which the next read will occur. 
It keeps track of two values, the currently read value and the value at 
the time of the next read (again this only comes into play when your 
data interval and your timestep are not the same).

Kind regards,
  David

> *De :*Pauline GELIN
> *Envoyé :* jeudi 3 mai 2012 17:33
> *À :* 'David BRADLEY'; 'Matt Duffy <duffy at tess-inc.com> 
> (duffy at tess-inc.com)'; 'trnsys-users (trnsys-users at cae.wisc.edu)'
> *Objet :* problem of windows and layers definitions
>
> Hello,
>
> Using TRNSYS and TRNBUILD for many projects in our office, we have 
> twobasic questions with no answers in manuals or forum:
>
> -Concerning the definitionof a window, we would like to know if Ug 
> presented in the library already includes convective heat transfer 
> coefficients (if so what value?) and the standard to which it is 
> calculated ?
>
> oIs this theexact value which is then used to calculate the Uw overall 
> coefficient window (taking the frame, the choice of spacer and also 
> the precise convective heat transfer coefficients asked)?
>
> oHowthese coefficients are they mathematically used (only for the 
> frame or also for the glazing already impacted by other coefficients 
> if I'm right)?
>
> -Concerning values of layers, and especially insulation materials, it 
> seems that theuser library savesonly two decimal places for 
> conductivity. If we specify three digits, the value is rounded and if 
> we add manually three decimal places in the file (opened by a 
> notepad), only the first two are considered. How can we fix this?
> Indeed, to convert and distinguish accurately conductivity values for 
> materials, it is necessary to have three decimal places.
>
> Thank you very much for your help.
>
> Best regards,
>
> Pauline Gelin
>
> Fluid and Environmental design engineer
>
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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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