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Re: [EnergyPlus_Support] RE:Thermal Conductance
For windows, the reported conductance DOES include nominal inside and
outside films. The window conduction reported in the eio is
deterimined by doing a heat balance calc on the window layers for
ASHRAE winter conditions, which are:
! Winter:
! Inside air temperature = 21.1C (70F)
! Outside air temperature = -17.8C (0F)
! Windspeed = 6.71 m/s (15 mph) ==> 25.47 outside
convective air film
conductance
! No solar radiation
The nominal outside convective coeff is the ASHRAE standard value
corresponding to 6.71 m/s wind speed. The inside convective coeff is
calculated by EnergyPlus assuming a vertical window.
If there is an air layer in the window, its resistance varies during
the simulation. For the eio report, the nominal conductance is
evaluated at the ASHRAE winter conditions listed above.
On 3 Jan 2003, at 8:27, Alexander Beisteiner wrote:
> Mike
> What about windows? Does the U-Value in the construction output
> represent a true figure or have the thermal resistances of inside and
> outside air surface films to be added as for other constructions?
> Regards Alexander
>
> __________________________________
> DI (FH) Alexander Beisteiner
> Forschungs- und Technologietransfer
> Pinkafeld GmbH
> Steinamangerstrasse 21
> 7423 Pinkafeld
>
> alexander.beisteiner@xxxxxxxxxxxxxxxxxx
> http://www.fh-pinkafeld.ac.at
> Tel.: 0043/3357/45370-1324
> Fax: 0043/3357/45370/1010
>
> -----Ursprüngliche Nachricht-----
> Von: Michael J. Witte [mailto:mjwitte@xxxxxxxx]
> Gesendet: Donnerstag, 02. Jänner 2003 20:57
> An: EnergyPlus_Support@xxxxxxxxxxxxxxx
> Betreff: Re: [EnergyPlus_Support] Thermal Conductance
>
> EnergyPlus does account for inside and outside film coefficients, but
> not in the way that this has traditionally been handled in many
> simulation programs.
> When a film coefficient is used in other
> programs, it is often a fixed value and does not vary.
> In
> EnergyPlus, not only does this value vary with the conditions of the
> surface and the surroundings, it can also split the radiation and
> convection terms into separate terms.
> This should result in a more
> accurate solution.
> The report value in the construction output only
> takes the user-defined portion of the wall construction into
> account.
> Note that it is possible to obtain the convection
> coefficients as output, if the user is interested in seeing its value
> or how it varies:
>
> Surface Int Convection Coeff[W/m2-K]
> Surface Ext Convection Coeff[W/m2-K]
>
>
> On 2 Jan 2003, at 16:51, Alexander Beisteiner wrote:
>
> > Dear E+ User
> > Looking at the construction output file, I found that the thermal
> > resistance (W/m²-K) of a construction is the sum of the resistances
> > of all layers- of course. But what about the thermal resistance of
> > inside and outside air surface film? Does not E+ account for these
> > values? I am looking forward to your comment. Regards Alexander
> >
> > __________________________________
> > DI (FH) Alexander Beisteiner
> > Forschungs- und Technologietransfer
> > Pinkafeld GmbH
> > Steinamangerstrasse 21
> > 7423 Pinkafeld
> >
> > alexander.beisteiner@xxxxxxxxxxxxxxxxxx
> > <http://www.fh-pinkafeld.ac.at/> http://www.fh-pinkafeld.ac.at
> > Tel.: 0043/3357/45370-1324
> > Fax: 0043/3357/45370/1010
> >
> >
> >
> > [Non-text portions of this message have been removed]
> >
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