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Re:Re:Re: [EnergyPlus_Support] A question about the center-of-glass conductance
Dear Mike
Thanks very much for your example file.
I have solved my problem.
In your exmple file,the inside convection algorithm is detailed, and in my file this value is simple.
If I change this vaule to detailed, the two U-value is almost same.
Thanks again
Lei
在2007-11-01，"Michael J. Witte" <mjwitte@xxxxxxxx> 写道：
I've run my own comparison and get a simulated u-value of 3.55 vs. a reported u-
value of 3.57. I used the ConvectionCoefficients object to force the exterior
convection coefficient to the stated nominal value of 25.47 W/m2-K.
See Window U-Value.zip in the Examples folder in the files area of the yahoo
group for inputs, outputs, and comparison spreadsheet.
http://tech.groups.yahoo.com/group/EnergyPlus_Support/files/Examples/Window%20U-
Value.zip
Mike
On 31 Oct 2007 at 9:15, wanglei wrote:
> Dear Mike
>
> I have tried to simulate my model as your suggestion.
>
> I set the IRHemispherical Emissivity : Front side and Back Side as 0.0001
>
>
> The conductance of single-pane system is 3.519 w/m2-K in the EIO file.
>
> The output results is:
> The Window Heat Loss is 490.7W ;
> The Ext Convection Coeff is23.68W/m2-K;
> The Int Convection Coeff is 3.076W/m2-K.
> The Outdoor Dry Bulb is -17.8 oC
> The Zone Mean Air temperature is 21.1
>
> The calculated results of the conductance is 2.68 w/m2-K
>
> By the way, the vaule of skyclearness is 0 in my designDay object so solar
> radiation isn't considered.
>
> I don't know why the calculated results less than the value in the EIO file.
>
> Thanks
>
> Lei Wang
>
>
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>
> 2007-10-31,"Michael J. Witte" <mjwitte@xxxxxxxx> :
>
>
> I suspect that radiant heat transfer inside and outside are affecting your
> results. Repeat your test with a simple single-pane construction and set the IR
> Hemispherical Emissivity: Front Side (and Back Side) to 0.00001 to supress
> radiant transfer. Does this compare better?
>
> For a double-pane system, you will need to define two instances of the glass,
> one with IR Hemispherical Emissivity: Front Side set to 0.00001 and another with
> IR Hemispherical Emissivity: Back Side set to 0.00001. You need to keep the
> radiant transfer across the window gas active.
>
> Mike
>
> On 30 Oct 2007 at 10:19, wanglei wrote:
>
> > Dear Linda
> >
> >
> > Now I create a single zone model with a south window without Frame and
> > Divide. The window area is 4.5m2.
> >
> > According to the ASHARE winter conditions, I create a HeatDesign Day:
> > The outside temperature is -17.8C
> > The wind speed is 6.71m/s
> >
> > The indoor temperature is 21.
> >
> > After calculating, the Window Heat Loss is 490.7W ; the Ext Convection Coeff
> > is 23.68W/m2-K; the Int Convection Coeff is 3.076W/m2-K.
> >
> > I use the formula k=Q/(tin -tout)/A to calculate the window u value
> >
> > The result is 2.8 W/m2-K. In eio file, this value is 3.785 W/m2-K
> >
> > Could you tell me why these two value isn't equal
> >
> > Thank you
> >
> > Lei wang
> >
> >
> >
> >
> >
> > [Non-text portions of this message have been removed]
> >
> >
> >
> > 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
> >
> >
> >
> >
> >
>
> ========================================================
> Michael J. Witte, GARD Analytics, Inc.
> EnergyPlus Testing and Support
> EnergyPlus-Support@xxxxxxxx
>
>
>
>
>
> [Non-text portions of this message have been removed]
>
>
>
> 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
>
>
>
>
>
========================================================
Michael J. Witte, GARD Analytics, Inc.
EnergyPlus Testing and Support
EnergyPlus-Support@xxxxxxxx
[Non-text portions of this message have been removed]
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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.
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