Thank you David for your quick reply,
Indeed the floor is a boundary wall, however I fixed it at 18°C
annually, it's the default setting for Energy plus. It means that all
the year, the outside temperature of the Ground floor is 18°C.
I checked the inside temperature of the ground floor, its varies,
according to the air temperature of course.
Actually, I checked all the inside surface temperatures of the box,
they are all below those of Energy plus calculations (by around 4°C
in summer). About the outside surface temperatures, the amplitude is
smaller in TRNSYS compare to Energy+. Which makes me think that
Energy+ takes something into account that TRNSYS doesn't for the
outside temperature of the surfaces, but I don't know what it could be.
If the temperature difference was only less than 1or 2°C, I would
think that the cause is the calculation method of the 2 programs. But
here I think the temperature difference is too big to be only that.
Do you have any clue?
King regards
Wirich FREPPEL
Doctorant Recherche & Developpement
Noirot
8 rue Ampere, 02000 Laon
03 23 27 31 99
Le 03/09/2014 15:34, David BRADLEY a écrit :
Wirich,
If you are using Trnsys17 then there is almost certainly an
automatic connection of solar radiation between the weather data
reader and the building because in TRNBuild the default selection is
that those connections will be made for you.
I would guess that the difference lies in how you have treated the
floor of your zone. If you created a BOUNDARY wall for your floor
then Type56 is expecting you will provide a temperature on the back
side of the floor (i.e. the interface between the floor and the
soil). If you did not make a connection to the boundary temperature
Type56 input then it is probably set to a constant value of 0 C,
which would keep your zone temperature quite low throughout the year.
Regards,
David
On 8/28/2014 03:30, FREPPEL Wirich wrote:
Hello everyone,
I'm running some tests in order to compare TRNSYS to another
software, which is Energy+.
My model is simple, a 3 meters long cube, with the same composition
for all the faces, without windows.
What I did in first place, was to create a new multizone project
using an idf file created from sketch up. Then I runned the
simulation in order to observe the evolution of the air temperature
inside the box.
Comparing it to Energy+ results, I noticed that in summer, the
temperature is far below those of Energy+. So I looked at the
connections in simulation studio to see if there was a problem on
the solar radiation on the walls, and I noticed that initially,
there are not any connection which give the solar radiation on the
walls.
My conclusion is that to take account of the solar radiation on
walls, we have to link it by ourself at the beginning, is it right
or did I miss something?.
Furthermore, in the "wall type manager", there's a tab called
"Solar Absorptance of wall". When I change the value, nothing
change regarding the temperature inside the box. So when is this
value used exactly?
Thank you in advance.
King regards