AW: [EnergyPlus_Support] IR Hemispherical Emissivity

["Alexander Beisteiner" <alexander.beisteiner@xxxxxxxxxxxxxxxxxx>]

Dear Mr. Witte
Thank you for your explanation, but the term "IR Hemispherical
Emissivity" is still unclear to me. As you mentioned, if glass does not
absorb energy, the field "IR Transmittance at Normal Incidence" is set
to zero. So, if energy is not absorbed by the material, heat exchange
(longwave radiant exchange) cannot happen. What role does the field "IR
Hemispherical Emissivity" play in this consideration?
Furthermore, I want to produce opaque windows which do not allow visible
transmittance and do not absorb energy: is it true to set the fields
"Solar Transmittance at Normal Incidence" and "Visible Transmittance at
Normal Incidence" to zero and the fields "Solar Reflectance at Normal
Incidence" and "Visible Reflectance at Normal Incidence" to one? 
I would appreciate your help.
Regards 

-----Ursprüngliche Nachricht-----
Von: Michael J. Witte [mailto:mjwitte@xxxxxxxx] 
Gesendet: Montag, 21. Oktober 2002 19:06
An: EnergyPlus_Support@xxxxxxxxxxxxxxx
Betreff: Re: [EnergyPlus_Support] IR Hemispherical Emissivity

No.  "IR Hemispherical Emissivity" is a surface property which 
applies to longwave (infrared, IR) radiant exchange.  If I understand 
your question correctly, you are trying to set absorption of energy 
within the glass thickness to zero.  For longwave infrared, this 
property is controlled by "IR Transmittance at Normal Incidence".

Mike



On 21 Oct 2002, at 15:01, Alexander Beisteiner wrote:

> Dear Madam/Sir
> With reference to the field "IR Hemispherical Emissivity" in the
> object Material:WindowGlass, may I assume that emissivity equals
> absorbtion. If I want to set absorption coefficients for glass zero,
> may I set the fields for front and back side zero?
> 
> Alexander Beisteiner
> __________________________________
> alexander.beisteiner@xxxxxxxxxxxxxxxxxx
> Forschungs- und Technologietransfer
> Pinkafeld GmbH
> Steinamangerstrasse 21
> 7423 Pinkafeld
> 
> http://www.fh-pinkafeld.ac.at <http://www.fh-pinkafeld.ac.at/> 
> Tel.: 0043/3357/45370-1324
> Fax: 0043/3357/45370/1010
> 
> 



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