[esp-r] Re: Zero Stack Pressure

Wed Jun 23 14:54:44 BST 2010

Hi Achim,

By chance, I found that the stack pressure was NOT zero ever. The problem is
only in the result visualisation in the esp-r result analysis...

I have tested your suggestions one by one. Confusingly, the results for the
stack pressure was always zero! Finally, I have tried the exemplar model
(alternative facade ...) and it was the same! I get curious to check some
other variables to see how it is possible. Surprisingly when I added the
volume flow rates to the selections, the stack pressures are changed to some
new values! :-0 (See the attachments). Un/Fortunately, in my models' results
it was the same story. ;-)

By the way it seems that the AFN simulation can solve such networks.
Hensen's thesis suggests an alternative stack pressure calculation for "an
extensive network containing several internal nodes with "long" flow paths"
on page 4-11 (page 58 of 197). I have tested this one as well but
differences between the measurements and the simulation results still
remain.

All the best,

Mostapha

On Fri, Jun 11, 2010 at 2:14 AM, Jon Hand <jon at esru.strath.ac.uk> wrote:

>
> If someone has a good atrium model that they have confidence in and which
> is well-documented then we could add it as an exemplar model for use
> in training workshops and/or self-study.
>
> Regards, Jon Hand
> ________________________________________
> From: esp-r-bounces at lists.strath.ac.uk [esp-r-bounces at lists.strath.ac.uk]
> On Behalf Of Achim.geissler [achim.geissler at intergga.ch]
> Sent: 10 June 2010 07:23
> To: MostaphaSadeghipour
> Cc: esp-r at lists.strath.ac.uk
> Subject: [esp-r] Re: Zero Stack Pressure
>
> Hi Mostapha
>
> in additio! n to the below, I think your approach with only one zone having
> external openings may be a general problem. The flow simulation can't really
> solve this, I think, because what you have is a possible flow path chain
> >in< the atrium (which is basically set up very good, I would think) which
> is singularily connected to the outside. Remember that one zone node can
> have only one temperature / pressure at one time step.
>
> Also, I would expect such a large atrium to have >some< leakage in the
> lower floor (entrance door etc.).
>
> Possible measures:
> a) Split the topmost zone into two (or three) that each have a connect to
> an exterior node
> b) also split the lowermost zone into two
> c) as written below, add some leakage to the lowermost zone
>
> Do the thermal results seem plausible? Do you have a "nice temperature
> stack" in the stacked zones?
>
> Best
> Achim
>
>
> --------- Original-Nachricht --------
> Von: "Achim Geissler" <achim.geissler at intergga.ch>
> An: "Mostapha Sadeghipour" <sadeghipour at gmail.com>
> Cc: "Aizaz Samuel" <aizaz.a.samuel at strath.ac.uk>, esp-r at lists.strath.ac.uk
> Betreff: [esp-r] Re: Zero Stack Pressure
> Datum: 09/06/10 23:13
>
> Hi Mostapha
>
> looking at your .a! fn, I think the problem is that all your connections to
> external nodes are in one zone (01).
>
> To get an afn up and running, a basic requirement is that for every zone
> you can go from an external node to a zone ... to >the< zone ... to a zone
> ... and so on and then to a (different) external node again. I think this
> does not hold for your afn. Add a connection type "tiny", e.g. a crack a
> factor 10 or 100 smaller than your _crk types and connect the lowermost
> zone(s) to an additional external node.
>
> Then something should happen and there should be pressure differences.
>
> Best
> Achim
>
>
>
>
> On Jun 9, 2010, at 2:47 PM, Mostapha Sadeghipour wrote:
>
> Hello Aizaz,
>
> I think the problem is not the node heights in my case, however I'm not
> sure. The .afn file is attached.
>
> Regard! s,
>
> Mostapha Sadeghipour
>
> On Wed, Jun 9, 2010 at 3:54 PM, Aizaz Samuel <aizaz.a.samuel at strath.ac.uk
> <mailto:aizaz.a.samuel at strath.ac.uk>> wrote:
> Look up how node heights are defined in exemplars>network
> ventilation>alternative facade vent.....
>
> Theory can be found in Jan Hensen's thesis (section 4.3.2) available at
> http://www.esru.strath.ac.uk/publications.htm
> --
> Dr Aizaz A Samuel
> Department of Mechanical Engineering
> University of Strathclyde
> M324 James Weir Building
> 75 Montrose Street
> Glasgow, UK
> G1 1XJ
>
> T:+44 141 548 5765
> F:+44 141 552 5105
>
> On Wednesday 09 June 2010 11:28, Mostapha Sadeghipour wro! te:
> > Dear esp-r users,
> >
> > I'm modeling an atrium with a closed glass roof. The atrium has nearly
> 16m
> > height and it only connects to the outside through 3 cracks on the roof.
> I
> > divided the atrium into 5 vertical zones, and adjacent vertical bypass
> > zones. They are connected to each other through fictitious faces.
> >
> > Common orifice components connect zone nodes to each other vertically,
> and
> > door component connects zone nodes to bypass nodes horizontally. The
> > attached image shows the Air Flow Network in my model more clearly.
> >
> > I supposed that esp-r includes the stack effect whenever delta height
> > between the nodes and the component is not zero. So I expected to have a
> > stack pressure in the vertical connections. But when I check the results
> > the stack pressure in the connections are zero!
> >
> > I'm also curious! how esp-r consider the stack effects and the gravity?
> The
> > components dP are set manually and there is no "g" in the equations?
> Where
> > I can find the PSTACK equations that is used to calculate DP:
> > DP=PRES(IDPS)-PRES(IDNE)+PSTACK(ICNN).
> >
> > Thanks in advance.
> >
> > Mostapha Sadeghipour
>
>
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>
>
>
>
>
>
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