[esp-r] Re: simulation message - non-convergence of air flow networks

Mon Oct 28 17:29:04 GMT 2013

OK Jon, 

thank you! I have made a clear drawing of my network and I have just printed out the flow network file in attachment. At the end on the file there are a series of nul values, do you think that could be the problem? How can I solve it? Once I have checked that every node and component has a connection and a flow path to a boundary pressure how can I check that the iteration convergence control is not too strict? 

Let me know,

All the best,

Arianna 

-----Original Message-----
From: Jon Hand [mailto:jon at esru.strath.ac.uk] 
Sent: 28 October 2013 16:52
To: Arianna Sdei; Achim Geissler; Aizaz Samuel
Cc: esp-r at lists.strath.ac.uk
Subject: RE: [esp-r] Re: simulation message - non-convergence of air flow networks

It is ALWAYS GOOD to clearly draw (on paper) your flow network with every name of every entity in the network file shown on your sketch.  Use coloured pens to draw the connections between nodes and components.  

If you are controlling components - like a window - if that is the only connection between the room and the outside then you should also have a crack defined between the room node and the boundary node.

And print the flow network file or the section of the model contents report related to network flow and control.  Go though each item and each connection and ensure that the sketch and the file is consistent.

Regards, Jon Hand

________________________________________
From: esp-r-bounces at lists.strath.ac.uk [esp-r-bounces at lists.strath.ac.uk] on behalf of Arianna Sdei [A.Sdei at brighton.ac.uk]
Sent: 28 October 2013 16:39
To: Achim Geissler; Aizaz Samuel
Cc: esp-r at lists.strath.ac.uk
Subject: [esp-r] Re: simulation message - non-convergence of air        flow    networks

Hi Achim,

thank you for that! How can I do convergence checking? Is there any way ESP-r can automatically check if there is a problem with the airflow network? I have tried with smaller time steps but no change. Let me know,

Regards,
Arianna

From: esp-r-bounces at lists.strath.ac.uk [mailto:esp-r-bounces at lists.strath.ac.uk] On Behalf Of Achim Geissler
Sent: 27 October 2013 16:47
To: Aizaz Samuel
Cc: esp-r at lists.strath.ac.uk
Subject: [esp-r] Re: simulation message - non-convergence of air flow networks

Dear Arianna,

in addition to the below, it sometimes helps to reduce simulation time steps (increase number of steps per hour). Also, you can change the parameters used for convergence checking (either every run manually or in the code and recompile).

Best
Achim

On Oct 22, 2013, at 9:04 AM, Aizaz Samuel <aizaz.a.samuel at strath.ac.uk<mailto:aizaz.a.samuel at strath.ac.uk>> wrote:

Arianna,

Somewhere in your model there is mass imbalance that is more than the tolerance allowed within the solver. Usually happens if you close a flow path using control (e.g. window closes but air is still being blown into the room from a fan). I would recommend to check this by removing control and then running the model. Another way forward is to make a sketch of the flow network and visually check if a bad flow path occurs given the constraints of the control you are trying to impose. A usual solution is to always have a flow path from internal nodes to external ones via small cracks (which is correct for most situations).

Another (rarer) reason is that you may have two components in series that have hugely different flow resistances.

Regards,
Aizaz

On 22/10/13 12:22, Arianna Sdei wrote:
Dear All,

I am simulating using an air flow network and while running the simulation I get the following message:

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

Can someone help me to interpret what that means and what should I look at in the model? Thank you,

Arianna

Arianna Sdei

Research Fellow IFORE (Innovation For Renewal)

UNIVERSITY OF BRIGHTON

Moulsecoomb, Lewes Road, Brighton, BN2 4AT

direct line: 0044 (0)2036747268

mobile: 0044 (0)7981739024

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