[esp-r] Re: MZELWE Longwave Flux Messages

[Holger Bertling]

Hi All,

do you mean the "Zone side: time-steps/hour"?
First it was 12 steps
and I increased ist up to 60 steps
and the Messages increased, too.
So it seems to be the material.

Is "Zone side: time-steps/hour" the right switch?
What is in your opinion a good time-step-value?

Best regards,
Holger



Am Mittwoch, den 15.10.2008, 09:35 -0400 schrieb Ferguson, Alex:
> >This was caused by the choice of high exterior surface
> >absorptivity and emissivity values, low specific heat, 
> >and low thermal conductivity.
> 
> The low specific heat and conductivity, and the high absorptivity and
> emissivity values translate into a small thermal time constant for the
> state equation describing the temperature of the surface. The simulation
> becomes unstable when the solution time step approaches (or exceeds)
> this time step; increasing the time resolution may also produce more
> stable simulations. 
> 
> - Alex 
> 
> -----Original Message-----
> From: esp-r-bounces at lists.strath.ac.uk
> [mailto:esp-r-bounces at lists.strath.ac.uk] On Behalf Of Lukas Swan (Dal)
> Sent: Wednesday, October 15, 2008 8:02 AM
> To: 'Holger Bertling'
> Cc: esp-r at lists.strath.ac.uk
> Subject: [esp-r] Re: MZELWE Longwave Flux Messages
> 
> Hi Holger,
> I have seen this in simulations before as well. It means that the long
> wave flux from the exterior building surfaces is greater than a typical
> expected range. I added a bit of verbosity to the source code once and
> found that it was always caused by my exterior surface temperature being
> too high. This was caused by the choice of high exterior surface
> absorptivity and emissivity values, low specific heat, and low thermal
> conductivity.
> 
> Take a good look at the materials you are using and how they are
> situated into the construction. Adjust some of these values and the
> issue will likely decrease.
> 
> Lukas Swan
> Dalhousie Univ.
> Canada
> 
> -----Original Message-----
> From: esp-r-bounces at lists.strath.ac.uk
> [mailto:esp-r-bounces at lists.strath.ac.uk] On Behalf Of Holger Bertling
> Sent: October-14-08 1:34 PM
> To: esp-r at lists.strath.ac.uk
> Subject: [esp-r] MZELWE Longwave Flux Messages
> 
> Dear All,
> 
> during my simulations I get a lot of these messages:
> 
> Wall-6:Raum_3 @ increment 31883
>  This is considered high and a correlation will be used.
>  <sky =  -222.7 <buildings = -145.3 <ground = -197.0
>  MZELWE: a longwave flux of   -578.9 Watts has been calculated for
> Wall-6:Raum_1 @ increment 31884
>  This is considered high and a correlation will be used.
>  <sky =  -228.3 <buildings = -147.9 <ground = -202.8
>  MZELWE: a longwave flux of   -496.6 Watts has been calculated for
> Wall-6:Raum_3 @ increment 31884
>  This is considered high and a correlation will be used.
>  <sky =  -197.3 <buildings = -126.0 <ground = -173.3
>   50 %   complete; expected finish time : Tue Oct 14 18:14:36 2008
>  MZELWE: a longwave flux of   -538.3 Watts has been calculated for
> Wall-6:Raum_1 @ increment 79966
>  This is considered high and a correlation will be used.
>  <sky =  -213.7 <buildings = -136.3 <ground = -188.3
>  MZELWE: a longwave flux of   -655.9 Watts has been calculated for
> 
> Does anybody know,
> what that means
> and if its bad or OK?
> 
> Thanks in advance,
> Holger
> 
> 
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