[esp-r] Problem with airflow network

[Liam O'Brien]

Hello everyone,

I'm setting up a fairly rudimentary airflow network, in which two zone air nodes exchange air with a third node that is intended to mix the air and send it back to the nodes.  A fixed volume rate component moves the air.  The "mixing" node was assigned to known boundary conditions of P=0 Pa, T=20C.  However, after several tries, I continue to get the following message for each timestep:

Please check (in the following order) that:                                                                                 
 - each node has some flow path to a boundary pressure and                                                                  
 - iteration convergence control is not too strict.                                                                         
 Day  2 Month  1 Hour 24.000:  100 iterations; flows solution failed 

I assume the first issue is triggering the message.  I would have thought that having the mixing node at known conditions would alleviate this error.  

Any thoughts?  (I realize this could be accomplished in the operations file, but I want something more sophisticated eventually.)

The afn file is below.


Thanks very much!

Liam O'Brien     

----------------

    3    1    4    1.000    (nodes, components, connections, wind reduction)
 Node         Fld. Type   Height    Temperature    Data_1       Data_2
 south           1    0   2.5000       20.000       0.0000       250.01    
 north           1    0   2.5000       20.000       0.0000       250.01    
 Mixing          1    2   20.000       0.0000       0.0000       2.0000    
 Component    Type C+ L+ Description
 Circulation    30  2  0 Constant vol. flow rate component   m = rho.a               
  1.  0.200000003
 +Node         dHght   -Node         dHght   via Component
 south         8.750   Mixing       -8.750   Circulation                             
 north         8.750   Mixing       -8.750   Circulation                             
 Mixing       -8.750   south         8.750   Circulation                             
 Mixing       -8.750   north         8.750   Circulation 

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