[TRNSYS-users] Virtual Surfaces + Stratification

[Ajit Naik]

Hello,

I am trying to model a very simple, MAU-conditioned, rectangular warehouse that's experiencing some condensation on the walls in Trnsys3d. As such, I've divided it into a central, rectangular core zone and four trapezoidal perimeter zones. I have further subdivided each of these zones into 3 stratification layers, for a total of 15 zones in Sketchup (screenshot attached) . I then assigned the surfaces dividing the zones as virtual surfaces, and combined all of the airnodes into one zone in Trnbld to allow radiation in the entire model. The existing heating is modeled via a ventilation type; the middle section of the perimeter  zones' exterior walls will undergo temperature-controlled wall gains to represent additional IR heating. I noticed that whenever I run the model, I am getting NaN error values for all airnode temperatures in Trnsys. So, my questions are as follows:


-          Is this due to the fact that the interior airnodes have only zero or one real surfaces? I recreated this model with both no stratification and with two stratification levels and noticed that the model ran fine in the case with no stratification (all airnodes bounded by at least 2 real surfaces) but failed in the case of 2 stratification layers (again core airnodes only have one real bounding surface).

-          If this is the case, what is the best way of addressing this issue - won't assigning real surfaces between the perimeter and core zones on each layer block internal radiative effects?

-          The building is currently conditioned via a ventilation type in the top core airnode; this airnode is linked to neighboring airnodes by coupling airflows that are fractions of the ventilation type airflow. Is there a better way of handling this?

Thanks in advance for all of your advice on what I hope is an easy problem!!!

Ajit Naik
Energy Engineer
dbHMS
303 W Erie Street, Suite 510
Chicago, IL 60654
p (312) 915-0557 x308
f  (312) 915-0558
www.dbhms.com

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