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RE: [EnergyPlus_Support] Re: AFN Node Pressure Distribution & Air Density & STACK
Tobias:
For your first question, Yes. However, you are restricted to what the model
provides. Please let me know what happens when you try it.
For your second question, horizontal openings can provide one way flows
driven by the pressure difference and two-way flows driven by buoyancy. The
object does not generate air stratification automatically. I have not tried
it.
Thanks.
Lixing
-----Original Message-----
From: EnergyPlus_Support@xxxxxxxxxxxxxxx
[mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx] On Behalf Of tobiasschulzeoooitu
Sent: Monday, May 03, 2010 2:24 PM
To: EnergyPlus_Support@xxxxxxxxxxxxxxx
Subject: [EnergyPlus_Support] Re: AFN Node Pressure Distribution & Air
Density & STACK
Dear Lixing (or anybody else who was dealing with this before),
one more - may be a misunderstanding with the therm "thermal chimney" in the
correspondence before.
1) Is it possible to use the AFN for a internal stack connecting zones in
different floors, which is not utilizing solar radiation to enhance the
natural ventilation - only using the inside outside temperature differences
and stack hight (chimney - but no solar chimney).
2) I also read some different opinions about an atrium design with vertical
zone stratification. Is that generally possible with horizontal openings
(not considering entering solar radiation)? Or should here better used a
single central and tall zone?
Thank you again,
Tobias
--- In EnergyPlus_Support@xxxxxxxxxxxxxxx, "stray359" <steve.d.ray@...>
wrote:
>
> Hi all,
>
> Does anyone know the planned future work for the AirFlowNetwork model? Are
any capabilities currently being expanded for future E+ versions?
>
> From whom or where can I find out?
>
> Thanks for your help,
> Steve
>
> --- In EnergyPlus_Support@xxxxxxxxxxxxxxx, Lixing Gu <gu@> wrote:
> >
> > Tobias:
> >
> > The existing AirflowNetwork model does not address the thermal chimney
yet.
> > A horizontal opening is manly used to introduce a circular flow between
two
> > zones.
> >
> > Thanks.
> >
> > Lixing
> >
> > -----Original Message-----
> > From: EnergyPlus_Support@xxxxxxxxxxxxxxx
> > [mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx] On Behalf Of
tobiasschulzeoooitu
> > Sent: Monday, May 03, 2010 7:49 AM
> > To: EnergyPlus_Support@xxxxxxxxxxxxxxx
> > Subject: [EnergyPlus_Support] Re: AFN Node Pressure Distribution & Air
> > Density
> >
> > Dear Lixing,
> > Thank you for your prompt answer. I have one more question about
vertical
> > airflow in the AFN which for I first should describe my model a little.
> > I try to connect several floors of a high rise building to a common used
> > thermal chimney. So this stack has openings on different heights to
> > different zones. I simulated the case 1) with one chimney zone 2) multi
> > chimney zones (one per floor) connected by horizontal openings (90deg
Cd=1).
> > With the one zone chimney i had a faster decrease of flow rates from
bottom
> > to higher floors than with the multi zone model.
> > Anyway, my question is, if it is a meaningful way to connect more than 2
> > zones vertically by horizontal openings? What are the restictions here?
> > There is one example file available, where only two zones are stacked
> > (AirflowNetwor_Multizone_HorizontalOpening.idf). Would the model work,
if
> > more zones are stacked, for example in stairways, elevator stack, atrium
or
> > double skin facade? I wonder if the AFN Restriction In-Out-Ref also
counts
> > for horizontal openings connections or if it was written before the
> > introduction of horiz.open. in E+.
> >
> > "Air circulation and/or air temperature stratification within thermal
zone.
> > For example, you should not try to divide a high space, such as an
atrium,
> > into subzones separated by artificial horizontal surfaces that have
cracks
> > or openings with the expectation that AirflowNetwork will give you a
> > realistic temperature in each subzone and/or a realistic air flow
between
> > subzones."
> >
> > If you would know a reference dealing with a similar problem, that would
be
> > also helpful for me.
> > Best regards,
> > Tobias
> >
> >
> >
> > --- In EnergyPlus_Support@xxxxxxxxxxxxxxx, Lixing Gu <gu@> wrote:
> > >
> > > My answers are under your questions.
> > >
> > > 1a) Where is the Zone_Node situated Floor/ceiling/center?
> > >
> > > A: Center.
> > >
> > > 1b) Is there a link to the room-air-model (temperature at a specific
> > height
> > > - if not mixed air)?
> > >
> > > A: No.
> > >
> > > 1c) could you please give the formuala for the zone 'AirflowNetwork
Node
> > > Total Pressure'? Especially how is the zone static pressure
calculated?
> > >
> > > A: The model uses the total pressure, The static pressure is not
> > calculated
> > > alone. The section of AirflowNetwork model in the Engineering
Reference
> > > provides detailed information.
> > >
> > > 2) For the calculation of the air density i used following formula,
which
> > > wasn't found in the eng.reference - but it gives slightly different
> > results:
> > >
> > > ρ=(P_atm (1+W_air))/(461,518(T_air+273,15)(W_air+0,62198))
> > [kg/m3]
> > > ρ = Air density [kg/m3]
> > > Patm = Outdoor barometric pressure at ground level [Pa]
> > > Wair = Air humidity ratio [kgWater/kgAir]
> > > Tair = Air Temperature [°C]
> > >
> > > A: the following equation is used to calculate air density
> > > rhoair = pb/(287.d0*(tdb+KelvinConv)*(1.d0+1.6077687d0*w))
> > >
> > > Lixing
> > >
> > > ------------------------------------
> > >
> > > The primary EnergyPlus web site is found at:
> > > http://www.energyplus.gov
> > >
> > > The group web site is:
> > > http://groups.yahoo.com/group/EnergyPlus_Support/
> > >
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a
> > > high speed connection. Limit attachments to small files.
> > >
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the
> > > Documentation link and press the "search" button.
> > > Yahoo! Groups Links
> > >
> >
> >
> >
> >
> > ------------------------------------
> >
> > The primary EnergyPlus web site is found at:
> > http://www.energyplus.gov
> >
> > The group web site is:
> > http://groups.yahoo.com/group/EnergyPlus_Support/
> >
> > Attachments are currently allowed but be mindful that not everyone has a
> > high speed connection. Limit attachments to small files.
> >
> > EnergyPlus Documentation is searchable. Open EPlusMainMenu.pdf under
the
> > Documentation link and press the "search" button.
> > Yahoo! Groups Links
> >
>
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