Reference:
Investigation of the Accuracy of Calculation
Methods for Conduction Transfer Functions of Building Construction
Dear All,
I am working in a simulation of
a historic building (with 70 thermal zones) in Porto Alegre city,
south of Brazil.
The building was constructed in the beginning
of 1900.
It´s a building with heavyweight walls.
The wall thickness in the 1st floor is (60 / 65) cm, in the 2nd
floor is (50 / 55 cm) and the 3rd floor is (40 / 45 cm). The wall
layers are constructed basically of bricks (10 cm) and
stucco (2,5 cm).
My question is regard with the method for
calculating the CTF used in EnergyPlus for heavyweight
constructions.
I have read some scientific
articles which present the numerical methods used
to calculate the CTF.
The more indicated to calculate the CTF for
heavyweight constructions is the Frequency-domain Regression Method, according
to the reference above.
EnergyPlus uses the State-space Method. This
method, according to the reference, may causes numerical divergences compared to
analytical solution obtained, depending on the Fourier of the simulation (time
step, thermal resistence and capacity).
Please, I would appreciate to know what is the
suitable method to calculate the CTF for heavyweight constructions.
/1/ Can I use the State-Space Method for this
simulation or the Difference Finite Method (CondFD) is more
indicated?
/2/ What is the State-space Method
working envelope?
I have already simulated the building with CTF
algorithm and the outcomes seem reasonable for the first
analysis.
I also simulated with CondFD algorithm and
the results of DX Coil Total Cooling (maximum value within the
design days for each zone) differ up to 20% less from the
values obtained by CTF.
Thank you in advanced.
Best regards,
Adriano Carotenuto.
Porto Alegre - Brazil
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