[TRNSYS-users] Active Layer and auto segmentation

[Avesani Stefano]

Hi David and hi all,

Thanks for your replying! If you have some more detailed information from TRNSsolar I will be happy to read them and further discuss!

 

Starting from your comments and useful questions I did some trials and thoughts.

Concerning autosegmentation button:

-      Autosegmentation does not appear as button if you create the *.bui from a 3D model (and this makes sense!)

-      Autosegmentation does appear if you start from a new *.bui without 3D model

o   It is not active if you have windows in your wall, even if the mindesmassflow is lower than minallowmassflo!!

 

Concerning the "minimum desired mass flowrate" and the "minimum allowable mass flowrate":

-      I don't understand  what should I write and which physical meaning has this parameter: is this the minimum flowrate I will let circulate in the alayer? (I then normally set the "inlet mass flow" as scheduled, but I set it higher than the minimum allowable internally calculated by trnsys...)

-      I don't know how the minimum allowable mass flowrate is calculated, even if from the math ref (pag.190&191) I understand that the min allowable massflowrate comes from 

mpoint*c*n*(Rw+Rr+Rx)>=1/2   à this hypothesis is needed in order to accept the hypothesis of linearization of the "tot resistance Rt"

Can someone confirm this?

If yes, the conclusion could be as follow: if the "min allowmassflr" is greater than the "min desmassflr" (set by user checking which minimum value of mass flow will be given to the AL??!?), in order to assure the reliability of the Rt linearization method segmentation is needed (smaller areas are obtained).

Do I have then to consider this AL areas as series (same massflow) or parallel (same Tin) connected?

And how is the "min allowmassflowr" dependent from the "number of loops" (where with "number of loops" I understand the number of turns the radiant pipe realize within the surface)?

 

Best regards

 

Stefano

 

 

 

Stefano,



Why is not the button "Divide surface" always present?

I am simulating a radiant wall with "standard" features (pipe spacing 15 cm, pipe ext diameter 2 cm, pipe thickness 2 mm).

the "divide surface" button is only needed if TRNBuild calculates that the specific mass flow rate (kg/h.m2) of the floor you are proposing is below the allowable limit. If the specific flow rate is below 13 kg/h/m2 then you have to segment the floor into multiple floors in series (and the "divide surface" button will become active.



 Furthermore, I have found no information about how the parameter "number of fluid loops" is taken into account in the mathematical model. Do you have any idea? 

Last question: how does TRNSYS calculate the minimum allowed inlet mass flowrate in case of a "number of fluid loops" greater than 1?

I am not sure about these but have forwarded the question on to our Transsolar colleagues. I will let you know as soon as I hear back from them.
Best,
 David



-- 
***************************
David BRADLEY
Principal
Thermal Energy Systems Specialists, LLC
22 North Carroll Street - suite 370
Madison, WI  53703 USA
 
P:+1.608.274.2577
F:+1.608.278.1475
d.bradley at tess-inc.com
 
http://www.tess-inc.com
http://www.trnsys.com
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