[esp-r] Re: Problem with airflow network

[Liam O'Brien]

Thanks, Jon and Monika.  Does the "known: boundary" type of node not count as a boundary node?  I specified its ambient temerpature and pressure as 20C and 0 Pa, repsectively.  Both unknown [zonal] nodes have connections to this node.

Liam



> From: jon at esru.strath.ac.uk
> To: obrien_liam at hotmail.com; esp-r at lists.strath.ac.uk
> Date: Fri, 10 Jul 2009 08:14:27 +0100
> Subject: [esp-r] Re: Problem with airflow network
> 
> 
> It is essential that there be at least one connection to a boundary node. The
> solver really needs this rule to be followed.
> 
> For more information on defining air flow networks there is a chapter in the
> current version of the ESP-r Cookbook (ESRU web page -> software downloads -> esp-r
> -> beginners guide
> 
> -Jon Hand
> ________________________________________
> From: esp-r-bounces at lists.strath.ac.uk [esp-r-bounces at lists.strath.ac.uk] On Behalf Of Liam O'Brien [obrien_liam at hotmail.com]
> Sent: 09 July 2009 20:24
> To: esp-r at lists.strath.ac.uk
> Subject: [esp-r]  Problem with airflow network
> 
> 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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