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

[Lixing Gu <gu@xxxxxxxxxxxx>]

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
> 
> 
> 
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Primary EnergyPlus support is found at:
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