[esp-r] Re: Zero Stack Pressure

[Achim.geissler]

    Hi Mostapha     in addition 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" 
 An: "Mostapha Sadeghipour" 
 Cc: "Aizaz Samuel" , 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 .afn, 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.
BestAchim



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&#39;m not
sure. The .afn file is attached.

Regards,

Mostapha Sadeghipour

On Wed, Jun 9, 2010 at 3:54 PM, Aizaz Samuel  wrote:
 Look up how node heights are defined in exemplars>network
 ventilation>alternative facade vent.....
 
 Theory can be found in Jan Hensen&#39;s thesis (section 4.3.2) available at
 http://www.esru.strath.ac.uk/publications.htm
(http://www.esru.strath.ac.uk/publications.htm" target="_blank)
 --
 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 wrote:
 > Dear esp-r users,
 >
 > I&#39;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&#39;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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