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Re: [EnergyPlus_Support] About exterior surface convection coefficient algorithms in EP



I think in design day calculation and it convert solar radiation into a "surface solar temperature" and use the temperature to do PRF. However it is a simplified way.

The way I know how to calculate convective heat transfer coeff based on wind speed is to use a 2nd order polynomial equation (empirical). I think is documented in E+ engineering reference. The wind speed is read from weather file.

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Best Regards

Kelvin Feng

On Tue, Jun 2, 2009 at 10:50 AM, Griffith, Brent <brent.griffith@xxxxxxxx> wrote:


I don?t know TAS and IES but is sounds like they are old fashioned models whose ?convection coefficient? actually combines convection and thermal radiation into a single coefficient.  That is what E+?s ?simple? model does. 

 

Combining convection and radiation into a single coefficient is a simplification that many older/simpler programs make to model heat flows.  But it is a poor approach when calculating surface temperatures.  

 

From: EnergyPlus_Support@xxxxxxxxxxxxxxx [mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx] On Behalf Of hvacgeshen516
Sent: Tuesday, June 02, 2009 12:57 AM


To: EnergyPlus_Support@xxxxxxxxxxxxxxx
Subject: [EnergyPlus_Support] About exterior surface convection coefficient algorithms in EP

 




If the algorithms except simple are chosen, the wind-driven convection coefficient will be much smaller than algorithms implemented by other software like TAS or IES.

Is there any comments on this?

Thanks and Regards
Xiangjing =)







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