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Re:Re: [EnergyPlus_Support] A question about the center-of-glass conductance
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
在2007-10-31，"Michael J. Witte" <mjwitte@xxxxxxxx> 写道：
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]
>
>
>
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>
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>
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>
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========================================================
Michael J. Witte, GARD Analytics, Inc.
EnergyPlus Testing and Support
EnergyPlus-Support@xxxxxxxx
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