Re: [TRNSYS-users] Sky temperature: which one to use?

["Kersken, Matthias" <Matthias.Kersken@ibp.fraunhofer.de>]

Good morning Mr. Badinier!

 

I would strongly recommend using the measured data from Your weather-file.

A calculated Sky temperature will always include the uncertainties of the physical model.

 

Kind regards,

    Matthias Kersken

--

Dipl.-Ing. Matthias Kersken
Department Energy Systems

Fraunhofer-Institute for Building Physics
Branch Holzkirchen
Fraunhoferstr. 10
83626 Valley, Germany

eMail: Matthias.Kersken@ibp.fraunhofer.de
Phone: +49/(0)8024/643-204
Fax:  +49/(0)8024/643-366
www.ibp.fraunhofer.de

 

---

Von: Francois Badinier [mailto:francois.badinier@icax.co.uk]
Gesendet: Donnerstag, 2. April 2009 16:35
An: Trnsys mailing list
Cc: David Bradley; Jeff Thornton
Betreff: [TRNSYS-users] Sky temperature: which one to use?

Dear TRNSYS community,

 

It seems that there are some differences between the ? Effective sky temperature? available in the weather component (e.g. Type 15-6) and the ?fictive sky temperature? calculated with the Type69b. The differences are quite important and I would like to know which one I should ?trust? to calculate some IR-emissions towards the sky.

 

I  attached a simple testing project in which I plotted the following graphs:

 

1.       The ?effective sky temperature? , straight from the weather component

2.       The  ambient (dry-bulb) temperature

3.       The average between ?effective sky temperature? and ?ambient temperature?

4.       The ?fictive sky temperature? calculated by the Type69b (using ?total diffuse radiation? as an input)

 

What comes out of this graph is that the ?average temperature? is quite close to the ?fictive sky temperature? calculated by Type69b.

So where do the differences come from and which temperature should I use?

 

Thank you for your help.

 

François Badinier

Development Engineer

ICAX Ltd

1 Hatfield House

Baltic Street West

London EC1Y OST

francois.badinier@icax.co.uk

www.icax.co.uk