[TRNSYS-users] Inside surface energy flux interpolation over the wall timebase

[Diego A. Arias]

Dear Pedro,

I have to admit that I am not an expert on z-transfer functions.  But 
from what I understand, the calculation of the coefficients for the 
transfer functions depends on the characteristics of the wall.  
Therefore, a very thin wall will result in coefficients that do not go 
too far back on time.  This could be the reason of the mathematical 
instability that you are seeing.  I put together a very simple example 
according to your description, and I got a very smooth response.  I will 
attach it in a separate email.

If you want, please feel free to send me your project. I will be happy 
to help you.  I will appreciate it if anybody else has a better explanation.
Best regards,

Diego


Pedro Rodrigo wrote:

>Hi all:
>
>We have developped a TYPE56 building model for control
>desing purposes.
>
>We are trying to identify transfer functions (G(s))
>for the zone energy gain, provided that only one
>external signal is exciting the zone (i.e. outside
>temp, solar radiation, etc..). 
>
>We excited the zone with a step function, varying the
>temperature difference between outside and inside air
>from 0 to 10ºCelsius in a single simulation timestep.
>Simulation timestep is set to 0.02 hours.
>
>The output for QCSURF (from TYPE56) showed a strange
>function. For each wall timebase (that is set to 1
>hour) the function starts with a high value (i.e. 2500
>kJ/h) and quickly decreases to get the zero value at
>the end of the hour; suddenly it jumps again to a high
>value and the process repeats.
>
>We don´t find an explanation to a such extrange energy
>response.
>
>Thanks for your suggestions.
>
>Regards,
>
>
>
>
>
>Pedro Manuel Rodrigo Cruz
>University of Jaen, Spain
>
>
>		
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-- 

Diego A. Arias
TRNSYS Coordinator
Solar Energy Laboratory
University of Wisconsin - Madison
1500 Engineering Drive
Madison, WI 53706