[esp-r] Re: Problem with airflow network

[Jon Hand]

In a dozen years of creating flow networks I have never had an occasion to
use a known fixed boundary type.  Boundary nodes are typically of type
wind pressure driven for most users.

Again, the design of flow networks is covered in the ESP-r Cookbook.  If someone has a really good use for
fixed nodes then I would be happy to include it in the Cookbook.

-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: 10 July 2009 14:15
To: esp-r at lists.strath.ac.uk
Subject: [esp-r] Re: Problem with airflow network

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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