[TRNSYS-users] type 9a, INTERPOLATION AND INSTANTANEOUS VALUES

[Diego A. Arias]

Dear Javier:

There are several parts to your question:
- First, TRNSYS' conventions for the values of the variables.  Michaël 
Kummert explained in a previous email that in TRNSYS, all variables are 
treated as "average values over the simulation time step (and the 
convention is that values are reported at the end of the time step). So 
if TRNSYS outputs an ambient temperature of 2.32 at TIME=2, it means the 
average temperature between 01:00 and 02:00 on January 1st was 2.32."
I would recommend that you follow the email thread in the emailing list 
archive:
https://www.cae.wisc.edu/pipermail/trnsys-users/2005/000785.html
http://sel.me.wisc.edu/trnsys/mailinglist/archive1999-2002/msg00735.html

- Second, the use of the proforma for Type9.  When you place an empty 
Type9 component from the Direct Access tree, you will see that there are 
only 10 parameters.  Parameter 3 asks for 'Number of values to read', 
and the default value is 1.  The Parameters 5 to 8 are telling the 
handling instructions for the input 1 in the data file.
If you change Parameter 3 to N, the lines (5+(n-1)) to (8+(n-1)), for 
n=1...N, are the corresponding instructions for each input in the data file.

- Third, and finally, the answer to your  question: 
-- If the column n in your data file was recorded as an average value 
during the the time step in the file, you do not want TRNSYS to average 
it for you one more time. Therefore, Parameter (8+(n-1)) = 0.    If the 
column n has an instantaneous value, the other components expect from 
Type9 an average over the time step; therefore, you should specify 
Paremeter(8+(n-1))=1, so Type9 calculates the average.
-- If you use the same time-step for your simulations and for your data 
input file, you do not need to interpolate between data points. 
Remember, this is independent from the averaging procedure explained 
above.  If your simulation uses a smaller time step, you may want to 
interpolate between data points; setting Parameter (5+(n-1)) to 1.

One test that you can perform is to set these parameters in order to see 
in TRNSYS the same values that you had in your input file.  This means 
that you assume that the values in your data file are averages during 
the time step, and that you are going to use the same time step for your 
simulations as for your input file. Use Parameter (5+(n-1))= -1, and 
Parameter (8+(n-1)) = 0, for all of the inputs in your data file.  By 
doing this, you will see the exact same data from your input file.

I hope this helps. Please let me know if you have additional questions.
Best regards,

Diego
 
javier mota wrote:

> Dear all:
> I am Javier Mota from 3i -ingenieria madrid in spain
> We are working with weather files, with data taken from zaragoza, a 
> city in spain.
> This data has been got with empirical and hourly measures.
> So i will use type 9a to read the data.
> Parameter 8 sayss: average or instantameous value-1.
> I remenber that parameter 8  used with parameter5,( interpolate or 
> not), makes that data used
> is not the same that the data fron the original file.
> So, my qwestion is:Parameter8,average or instantameous value-1, may 
> have some relation with the
> way empirical data were got?. So,if empirical data are average data in 
> an hour. I must use
> parameter 8 as average and interpolate or not.
> Or simply, This has no sense, and parameter 8 may be instantaneous 
> value even when the data file refers to averahe vaslues in time.
> So, When mus I used average or instantaneous and in relation with 
> parameter 8 how i mus work
> with parameter5, interpolate or not.
> Thanks in advance.
>
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