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Dear TRNSYS-Team and -users,
I am currently working with Type 56 and have two questions regarding the treatment of heat transfer in TRNBuild / Type 56.
1)
First, regarding the convective heat transfer coefficients:
In the Construction Types, I specify constant convective heat transfer coefficients for the front and back surfaces,
for example 9.72 and 72 kJ/h·m²·K.
However, in the Type 56 outputs, the reported values for the "effective" convective heat transfer coefficient are different from the input values.
This raises a few questions for me:
What exactly is the difference between the input convective heat transfer coefficient and the output “effective” convective heat transfer coefficient?
Is the effective value directly used in the simulation, or is it only a reported/post-processed output quantity?
Is it recalculated during the simulation depending on surface temperature, air temperature, or other boundary conditions?
-Because when i applied different room air temperatures it did not change. It seems to be purely dependent on the surface Area proportions?
Which physical or scientific model is implemented here?
I would have expected the effective convective coefficient to remain equal to the prescribed input value if a constant coefficient is defined.
Since this is apparently not the case, I would like to better understand the underlying formulation in Type 56.
2)
My second question concerns the definition of the category “Boundary” or “Boundary conditions”, especially when it is set to “identical”.
What exactly does “identical” mean in this context?
Does it mean that the heat fluxes on one side of the construction are mirrored to the adjacent side of the neighboring zone,
i.e. that convective and/or radiative heat exchange is transferred consistently between both zones?
Or does it mean that a temperature boundary condition is imposed on the other side?
I could also not find an unambiguous explanation of this point in the Trnsys-Documentation/ Literature.
Any clarification on either of these topics, or references to documentation or publications, would be greatly appreciated.
Best regards,
Alex Sz
TS_Team 27/03/2026 12:32 pm
Question 2):
Please refer regarding your question 2) to the following .PDF that offers an explanation.
