Re: [TRNSYS-users] problem of windows and layers definitions

Pauline,

On 5/16/2012 09:38, Pauline GELIN wrote:

Hello,

I am so sorry to insist but, 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 ?

I also appeal to you about another problem I have with each project on TRNSYS.

When I 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 is rather 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@tess-inc.com> (duffy@tess-inc.com)'; 'trnsys-users (trnsys-users@cae.wisc.edu)'
Objet : problem of windows and layers definitions

Hello,

Using TRNSYS and TRNBUILD for many projects in our office, we have two basic questions with no answers in manuals or forum:

-          Concerning the definition of 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 ?

o   Is this the exact 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)?

o   How these 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 the user library saves only 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

KATENE

10 avenue des Canuts – 69120 VAULX EN VELIN

0437453347

-- 
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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
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d.bradley@tess-inc.com

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