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RE: [EnergyPlus_Support] Re: AFN width & height factor / detailed opening



Sam:

I don't agree with you. This is the program limitation and can not be called
as a bug. 

Your suggestion sounds simple, but may require structure change. The
pressure variation is calculated in early stage once. A full height is used
to calculate pressure variation.

The real opening areas are calculated in the component level. The internal
iteration is required to get converged airflow rates for each component.
However, the program will not get back to the pressure variation subroutine
during iteration. 

A possible improvement is to assume linear relationship between pressure
variation and actual height at the component level. However, it may slow
down the program further. I need time to think through.

Thanks.

Lixing

-----Original Message-----
From: EnergyPlus_Support@xxxxxxxxxxxxxxx
[mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx] On Behalf Of samuel.brunswick
Sent: Wednesday, June 08, 2011 1:28 PM
To: EnergyPlus_Support@xxxxxxxxxxxxxxx
Subject: [EnergyPlus_Support] Re: AFN width & height factor / detailed
opening

Hi Lixing,

I'm jumping in on this discussion kind of late, but have run into the same
problem as Tobias and am hoping the bug can be fixed.

I understand that the limitations of the program prevent the pressure
variation calculation from being based on the modulating window opening
height, so the calculation is based instead on the window height, a
constant.  But wouldn't it be just as easy to base the pressure variation
calculation on the full window opening height, a constant, defined by
(window height)*(height opening factor).

An example of what I'm suggesting:

Window height = 3 = constant
Height opening factor = 0.5 = constant

Height used in pressure variation calculation = (3)*(0.5) = 1.5 = constant


This seems like a fairly easy fix that would give more accurate results; am
I missing something?

Thanks,

Sam




--- In EnergyPlus_Support@xxxxxxxxxxxxxxx, "tobiasschulzeoooitu"
<tobias.schulze@...> wrote:
>
> Dear Lixing,
> thank you for the explanation - I understand now. May be it is worth to
write this issue down in the I/O reference.
> 
> 
> 
> --- In EnergyPlus_Support@xxxxxxxxxxxxxxx, Lixing Gu <gu@> wrote:
> >
> > Tobias:
> > 
> > I checked the source code. The pressure variation due to height is
> > calculated based on the window geometry, regardless of real opening area
due
> > to modulation. The real opening area is used to calculate flow rate in
the
> > component level, such as detailed opening component. The program is not
> > advanced enough to make adjustment due to modulation. It is similar to
solar
> > entry through a window. It assumes windows are closed, regardless of
real
> > window position. The half open windows may generate its own shading for
> > solar entry.
> > 
> > Therefore, it is the program limitation and assumption. Since the real
> > opening areas and window geometry are the same in Cases 1, 2 and 3, the
same
> > results are expected.
> > 
> > Hope this helps.
> > 
> > Lixing
> > 
> >  
> > 
> > -----Original Message-----
> > From: EnergyPlus_Support@xxxxxxxxxxxxxxx
> > [mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx] On Behalf Of
tobiasschulzeoooitu
> > Sent: Wednesday, June 08, 2011 7:31 AM
> > To: EnergyPlus_Support@xxxxxxxxxxxxxxx
> > Subject: [EnergyPlus_Support] Re: AFN width & height factor / detailed
> > opening
> > 
> > Dear Linxing,
> > 
> > the opening factor AFN:Surface is 1 as you told me to check. And the
window
> > geometry is also same - BUT the flow rates should be different because
of
> > the different opening geometry (as part of the window geo) due to the
h&w
> > factors. Lets say due to the h&w in factors in AFN:DetailedOpening I
assumed
> > that in 1) the opening is 0,1m wide and 1m high. And in 2) the opening
is 1m
> > wide and 0,1m high -> different opening geometry -> should result in
> > different ACH.
> > 
> > 3) and 4) are geometrically modelled and 3) is close 1)&2) and 4) is
much
> > less (less height = less ACH = correct)
> > BUT therefore I assume 2) to be wrongly calculated. Should be close to
4)
> > 
> > I compare the "AirflowNetwork Zone Infiltration Air Change Rate". No
weather
> > file necessary -> only DesignDay. In & Outdoor temp is fixed
(20/24�C).
> > You can see that from the idf file containing all 4 scenarios. I will
send
> > you per mail (I hope it works).
> > 
> > What do you think?
> > 
> > Regards
> > 
> > 
> > 
> > --- In EnergyPlus_Support@xxxxxxxxxxxxxxx, Lixing Gu <gu@> wrote:
> > >
> > > Tobias:
> > > 
> > > There are two issues. The first issue is window opening factor. If the
> > > opening factor for Cases 1 and 2 are 1.0, both windows should get the
same
> > > flow rate due to the same geometry. Since the input files are not
> > attached,
> > > you may check the opening factor by yourself first.
> > > 
> > > The second issue is flow rate comparison. Since a two way flow is
> > expected,
> > > what flow rate do you compare, incoming flow, outgoing flow or a sum?
> > > 
> > > Please let me know what happens after check. You may also send your
input
> > > files and provide weather date file name if the weather file is
available
> > in
> > > the web site. Then you need to specify which part of output file (rows
and
> > > columns) make you think a program code fault. 
> > > 
> > > Thanks.
> > > 
> > > Lixing 
> > > 
> > >    
> > > 
> > > -----Original Message-----
> > > From: EnergyPlus_Support@xxxxxxxxxxxxxxx
> > > [mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx] On Behalf Of
> > tobiasschulzeoooitu
> > > Sent: Monday, June 06, 2011 12:09 PM
> > > To: EnergyPlus_Support@xxxxxxxxxxxxxxx
> > > Subject: [EnergyPlus_Support] AFN width & height factor / detailed
opening
> > > 
> > > Hello,
> > > 
> > > after some parametric analysis I realized, that for a single sided
> > > ventilation strategy, the volume flow is same for these two options:
> > > 1) width factor = 0,1 & height factor = 1
> > > 2) height factor = 0,1 & width factor = 1
> > > 
> > > One can assume, that the volume flow in case 1) is higher because of
the
> > > bidirectional opening model and higher density differences from top of
the
> > > opening to the bottom of the opening as the opening height is bigger.
> > > 
> > > Therefore I repeated the same cases, but changing the window geometry
> > > according the previously mentioned factors (leaving the factors as 1).
> > Here
> > > the resulting volume flow for 
> > > 3) opening width=0,1 & opening height=1
> > > is much higher than with a 
> > > 4) opening height=0,1 & opening width=1
> > > 
> > > This is as I assumed and flow for case 3)is very close to 1) & 2)
> > > 
> > > Concluding, there may be is a program code fault with the opening
factors
> > > when changing the height factor.
> > > 
> > > Unfortunately the analytic solution for the cases as it is described
in
> > the
> > > engineering reference is very difficult to realize but I can send the
3
> > idf
> > > test files.
> > > 
> > > Best Regards,
> > > Tobias
> > > 
> > > 
> > > 
> > > ------------------------------------
> > > 
> > > Primary EnergyPlus support is found at:
> > > http://energyplus.helpserve.com or send a message to
> > > energyplus-support@
> > > 
> > > 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
> > >
> > 
> > 
> > 
> > 
> > ------------------------------------
> > 
> > Primary EnergyPlus support is found at:
> > http://energyplus.helpserve.com or send a message to
> > energyplus-support@
> > 
> > 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
> >
>




------------------------------------

Primary EnergyPlus support is found at:
http://energyplus.helpserve.com or send a message to
energyplus-support@xxxxxxxx

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







------------------------------------

Primary EnergyPlus support is found at:
http://energyplus.helpserve.com or send a message to energyplus-support@xxxxxxxx

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.
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