[TRNSYS-users] Inside surface energy flux interpolation over the wall timebase
Diego A. Arias
daarias at wisc.edu
Tue Jan 17 08:28:48 PST 2006
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.
Pedro Rodrigo wrote:
>We have developped a TYPE56 building model for control
>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
>Thanks for your suggestions.
>Pedro Manuel Rodrigo Cruz
>University of Jaen, Spain
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Diego A. Arias
Solar Energy Laboratory
University of Wisconsin - Madison
1500 Engineering Drive
Madison, WI 53706
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