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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 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 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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