[EnergyPlus_Support] Re: Surface heat flux interpretation

["laurentvidal50" <laurent.vidal@xxxxxxxxx>]

E+ results are the same all day long. No shift.

I tried your idea using a material with 1 as specific heat and getting exactly the same value as I had with the R=1.

There is something else! thank you for your reply.

--- In EnergyPlus_Support@xxxxxxxxxxxxxxx, Edwin Lee <leeed2001@...> wrote:
>
> I believe the R-Value material still has some effective mass built in to
> ensure program stability.  This would cause variation.  Plot the E+ results
> with your steady state results for one day and see if there is a nice shift.
>  If the shift is there, the diff is probably the mass, if the shift is not
> the difference then there is something else going on.
> To have better control of the mass, you could consider using a regular
> material and specifying smaller and smaller specific heats until the program
> gives you something close to the steady state answer you are requesting.
>  However, stability issues may again come into play.
> 
> Edwin
> 
> On Wed, Apr 22, 2009 at 5:02 AM, laurentvidal50 <laurent.vidal@...>wrote:
> 
> >
> >
> > Hello,
> >
> > Looking to a surface heat transfer I can't understand how heat flux is
> > computed.
> >
> > In Winter Design Day calc (T out = -3.1°C, T int = 22°C).
> > The U value surface-to-surface is 1 (one layer with a R=1 material only).
> > My wall is 82.07 m2.
> >
> > Convection algorithms are Simple for interior and exterior. I set no wind
> > so that U convection int and out are those expected (Uc int = 3.076, Uc out
> > = 8.23). At surface level output show me these values.
> >
> > Now if I try to manually calculated heat transfer using convection given by
> > outputs I can't get the Heat loss calculated by E+.
> > E+ give me 1194 W when I find 1434 W.
> >
> > Where am I wrong?
> > May be this formula is not complete, does E+ uses another equation?
> > Heat = U-value-with-film x Surface x (T int - T out)
> >
> > Thanks for any tip
> >
> >  
> >
>




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

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 not allowed -- please post any files to the appropriate folder in the Files area of the Support Web Site.

EnergyPlus Documentation is searchable.  Open EPlusMainMenu.pdf under the Documentation link and press the "search" button.
Yahoo! Groups Links

<*> To visit your group on the web, go to:
    http://groups.yahoo.com/group/EnergyPlus_Support/

<*> Your email settings:
    Individual Email | Traditional

<*> To change settings online go to:
    http://groups.yahoo.com/group/EnergyPlus_Support/join
    (Yahoo! ID required)

<*> To change settings via email:
    mailto:EnergyPlus_Support-digest@xxxxxxxxxxxxxxx 
    mailto:EnergyPlus_Support-fullfeatured@xxxxxxxxxxxxxxx

<*> To unsubscribe from this group, send an email to:
    EnergyPlus_Support-unsubscribe@xxxxxxxxxxxxxxx

<*> Your use of Yahoo! Groups is subject to:
    http://docs.yahoo.com/info/terms/