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# Error in E+ AirflowNetwork distribution

Problem statement:

I am modeling infiltration rate through a block using energy plus......It is an air conditioned space. I have supply air flow rate and return air flow rate. through that I am finding out the static pressure inside the room....

then, because of outside pressure, there will be pressure difference between inside and outside and hence infiltration is prone to occur through envelope cracks....this is my problem statement

in this aspect, I faced a problem regarding Air flow network distribution model. please explain me about the errors, here is the IDF file

please have a look into this.....

These are the errors...

 ** Severe  ** ValidateDistributionSystem: COOLING COIL AIR OUTLET NODE is not defined as an AirflowNetwork:Distribution:Node object.
** Severe  ** ValidateDistributionSystem: MIXED AIR NODE is not defined as an AirflowNetwork:Distribution:Node object.
**  Fatal  ** ValidateDistributionSystem: Program terminates for preceding reason(s).
...Summary of Errors that led to program termination:
..... Reference severe error count=2
..... Last severe error=ValidateDistributionSystem: MIXED AIR NODE is not defined as an AirflowNetwork:Distribution:Node object.


Eventhough I defined Cooling COil Air Outlet Node and Mixed Air Node...Why am I still getting the same error...

please someone help to fix this error...and let me know your opinion on my methodology as well

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Yes, you have defined the nodes, but I don't think you've connected them up properly. For the cooling coil outlet, here's what you have:

AirflowNetwork:Distribution:Node,
Cooling Coil Air Outlet Node,  !- Name
,                              !- Component Name or Node Name
Other,                         !- Component Object Type or Node Type
1.5;                           !- Node Height {m}


And here is what the AirflowNetwork_MultiZone_House.idf example file has:

AirflowNetwork:Distribution:Node,
CoolingInletNode,              !- Name
Cooling Coil Air Inlet Node,   !- Component Name or Node Name
Other,                         !- Component Object Type or Node Type
3.0;                           !- Node Height {m}


You've created a AirflowNetwork:Distribution:Node object named "Cooling Coil Air Outlet Node" instead of one that refers to the outlet node of the cooling coil. I'm not sure where the other error is coming in, but you're using the name "Mixed Air Node" for both an air loop node and an AFN node so the IDF is somewhat hard to follow. I'd try to change the names so things are clearer and the nodes are differentiated. I suspect something is getting confused there. If I get a chance to run your file, I'll update my answer.

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but you're using the name "Mixed Air Node" for both an air loop node and an AFN node so the IDF is somewhat hard to follow......

@Jason DeGraw ok so you mean to say that the node that is defined in air loop node cannot be the same in AFN node...Am I right?

yeah...I observed it and changed the name......Now I did not get error regarding that but ended up getting in another error ....

Severe * AirflowNetworkSolver: L-U factorization in Subroutine FACSKY. * ~~~ * The denominator used in L-U factorizationis equal to 0.0 at node = MIXED NODE. * ~~~ ** One possible cause is th

( 2018-05-14 23:46:11 -0500 )edit

@Jason DeGraw.....in continuation to the above comment, * One possible cause is that this node may not be connected directly, or indirectly via airflow network connections * ~~~ * (e.g., AirflowNetwork:Multizone:SurfaceCrack, AirflowNetwork:Multizone:Component:SimpleOpening, etc.), to an external * ~~~ * node (AirflowNetwork:MultiZone:Surface). * ~~~ ** Please send your input file Now....what is this error correspond to? could you please please help me in resolving this..

( 2018-05-14 23:49:55 -0500 )edit

@Siva If the naming restriction was intentional, you should have gotten an error on that, so it might be a bug. The new error you see is often caused by a disconnect in the network, and instead of a single pressure network you have several. Try turning off the distribution simulation (there's a field in AirflowNetworkSimulationControl) and see if that works. The node that is indicated is a distribution node, so this is probably something about the distribution system. Make sure that your nodes actually form a loop and your overall network is all connected together.

( 2018-05-15 01:54:21 -0500 )edit

Is there any problem with the Return fan node. because I used that node on my own..I edited the already existing afn distribution file and I fixed mine....Actually in my case I have both supply and return air flow rates with me. I want energy plus to forcefully take those values and calculate the static pressure prevailing in the space and thereafter I wanted to find out the exact infltration or exfiltration due to outside pressures.....

so any error in my thinking and tell me any issues with return fan

( 2018-05-15 02:20:32 -0500 )edit

@BBel .......Hello.....I could see you too faced the same problem of L-U Factorisation Error......Could you please tell me did you able to rectify the problem?

( 2018-05-15 04:40:18 -0500 )edit