RE: [EnergyPlus_Support] Re: Finite difference method error

[YuanLu Li <yli006@xxxxxxxxxxx>]

Hi, Liam
 
I do not know exactly what you are calculating.
 
To me, it seem impossible to make a building complely no sun, no wind.

0.02°C with CTF is small compared with 3°C, but may mean that there are some differences in external conditions.
 
What about calculating the two zones one at a time at thier respective coordinate location, or changing the zone ordering in calculation?
 
Or repeat the calculation more than once to check for the steady state as suggested by  Candanedo?

 

 Dr. Li  

 

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To: EnergyPlus_Support@xxxxxxxxxxxxxxx
From: liambrn@xxxxxxxxx
Date: Sat, 24 Oct 2009 13:10:58 +0000
Subject: [EnergyPlus_Support] Re: Finite difference method error

 

Dr. Li,

Good thought, but the Conduction Transfer Function method yields results within 0.02C, as expected. I did rotate the building and get the exact same results. This shouldn't make a difference though, because wind and sun exposure were turned off.

Liam

--- In EnergyPlus_Support@yahoogroups.com, YuanLu Li <yli006@...> wrote:
>
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> Is the longer axis of the building, North-South, or East West?
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> Are the two zones joined with a partition or separate?
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> The sun and wind are turned off. What do you think would be the external conditions? DesignDay, sizing and normal run period may give different answers.
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> Turn the building around at different orientation angles and see how the values changes.
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> Dr. Li
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> To: EnergyPlus_Support@yahoogroups.com
> From: tincandanedo@...
> Date: Thu, 22 Oct 2009 23:03:48 +0000
> Subject: [EnergyPlus_Support] Re: Finite difference method error
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> This is interesting... Have you tried changing the time step? Another possibility is that the system hasn't reached steady state. Finally, is it possible to change the size of the control volume?
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> José Candanedo
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> --- In EnergyPlus_Support@yahoogroups.com, "liambrn" <liambrn@> wrote:
> >
> > I have created two adjacent zones with identical wall constructions, geometry and boundary conditions. I turned sun and wind exposure off. The temperatures are free floating. However, I'm seeing a difference of about 3C between the two zones throughout the day. The zones remain within ~0.2C using the ConductionTransferFunction method. Thoughts?
> >
> > Thanks.
> >
> > Liam O'Brien
> >
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