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Re: [EnergyPlus_Support] U-values in E+



No problem.  Thanks for confirming that the values are consistent.  Mike

On 20 Apr 2006 at 18:02, Clarice Bleil de Souza wrote:

> Dear Mike 
>    
>   Thanks a lot for the reply. 
>   I recalculate the conductance without the film coefficients and the values
> do match. E+ is reporting the conductance of the composition in the eio file
> and I thought it was reporting the U-value. The film coeff you are using are
> almost the same I used - 0.12 Rsi and 0.03 Rso. So everything matches - I just
> didn't realise that E+ was ploting the conductance instead of the U-value. My
> fault - sorry for that :(
>    
>   Thanks a lot for the reply
>    
>   Regards,
>    
>   Clarice
> 
> "Michael J. Witte" <mjwitte@xxxxxxxx> escreveu:
>   As you know, the surface details report (report, surfaces, details;) gives
> U-
> values with and without film coefficients.  The construction report (report,
> construction;) reports a thermal conductance without film coefficients, which
> should be the same value as the "Nominal U (w/o film coefs)".
> 
> For the "Nominal U (with film coefs)", there is a table of film coefficients
> given in the "Output Details and Examples" document, p. 26 (pdf p. 32).  I see
> that this table is in I-P units.  Here are the values in S-I units (which we
> will add to the document, but it might be too late to add for the 1.3
> release). 
> These values are directly from the source code:
> 
> Surface type, Interior film, Exterior film {m2-K/W}
> 
> Wall, 0.1197548 , 0.0299387
> 
> Floor, 0.1620212 , 0.0810106
> 
> Ceiling/Roof, 0.1074271 , 0.0810106
> 
> 
> Would you please repeat your hand calculations using the above values and 
> confirm if this agrees with the reported "Nominal U (with film coefs)"?
> 
> Mike
> 
> 
> 
> On 20 Apr 2006 at 13:03, Clarice Bleil de Souza wrote:
> 
> > Hi Everybody,
> >    
> >   I am trying to run some simulations with different U-values to check the
> > sensitivity of the results and I was wondering, how does E+ calculates the
> > U-values. 
> >   I have some material compositions that gives me 0.5w/m2K calculated by
> hand
> > (using Rso = 0.055 and Rsi = 0.123 - using the inverse sum of the
> > resistivities in series) and E+ gives me 0.55 which is near. Once I look for
> a
> > more conductive material with a hand calculated value of 3 w/m2K, Energy
> Plus
> > gives me a value of 6.5W/m2K. I could not understand why this is happenning.
> I
> > know the U-values won't be used by E+ but I want to be sure that results
> will
> > be somehow equivalent. Can you please let me know how E+ calculates the
> > U-values? I couldn't find anything about it in the documentation.
> >    
> >   Thanks a lot for your attention and hope hearing from you soon,
> >    
> >   Regards,
> >    
> >   Clarice
> >    
> >    
> > 
> >             
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> 
> 
> ========================================================
> Michael J. Witte, GARD Analytics, Inc.
> EnergyPlus Testing and Support      
> EnergyPlus-Support@xxxxxxxx
> 
> 
> 
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========================================================
Michael J. Witte, GARD Analytics, Inc.
EnergyPlus Testing and Support      
EnergyPlus-Support@xxxxxxxx





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