Dear TRNSYS users,
I have some problems with the active layer
module of TRNBLD, which I used for modeling a floor heating
system.
The active layers, which should be
displayed in the model, are defined as following:
Layer 1:
·
Pipe spacing: 24 cm
·
Pipe outside diameter:
16 mm
·
Pipe wall thickness: 2
mm
Layer 2:
·
Pipe spacing: 8 cm
·
Pipe outside diameter:
16 mm
·
Pipe wall thickness: 2
mm
By specifying the thicknesses of the layers
adjacent to the active layers, the following curiosity
appeared.
For case 1, I set the thickness of the
layer above the active layer to 73 mm, which is greater than
0.3 times the pipe spacing, and I set the layer below to 0.5
times the pipe outside diameter (requirements taken from
manual TRNSYS 17, 5-187, table). This step had worked pretty
good and the simulation was running without any problems.
In a second step, I revised the model and
included the second active layer into the TRNBLD model. As the
floor screed should be identical for both cases, I tried to
define the thicknesses of the adjacent layers the same way as
I did it in case 1. But when I tried to reduce the thickness
of the adjacent layer below, the following warning appeared:
“thickness must be in the range of 0.024 to 1.0”.
In order to understand this warning I had a
closer look to the manual of TRNBLD. On page 5-58 (TRNSYS 17)
I found a remark that both layers adjacent to the active layer
must be greater than 0.3 times pipe spacing. This would
explain, why the warning appears, but I do not understand, why
the first case should be unproblematic, as the required
minimum thickness in this case should be 72mm and why this is
not mentioned in the mathematical description.
Does anyone has an idea, what could be the
reason behind that, or might this be a known or unknown bug?
If this requirement dependent on the pipe spacing should be
really used for both layers, this would mean that extremely
thick floor screeds of +15cm are necessary to model a floor
heating system with a pipe spacing of 24 cm. This sounds
absolutely unrealistic.
Hoping for some help,
Kind regards,
Johannes Schrade