[esp-r] Re: absorptivity and absorption of 5 angles???

[Geissler Achim]

Dear Qiu,
the way it *should* be IMO is that all radiation-relevant properties are defined by the entry in the optics.db (at 5 angles). The thermal information is taken from the materials.db (called constr.db1 or constr.db2, typically).
Normally, any changes to "solar absorptivity" in the constr.dbx entries should *not* have any effect on simulation results. The emissivity, however, is taken from the constr.dbx.
Do you really find changes in results if you *only* change the solar absorptivity in the constr.dbx entry?

Regards,
Achim


> -----Original Message-----
> From: esp-r-bounces at lists.strath.ac.uk [mailto:esp-r-
> bounces at lists.strath.ac.uk] On Behalf Of Dr.QIU
> Sent: Wednesday, May 14, 2008 1:40 PM
> To: esp-r
> Subject: [esp-r] absorptivity and absorption of 5 angles???
> 
> Dear all,
> 
> In ESP-r's "material database", each type of glass has some properties as
> follows:
> 
> Thick 8mm
> Conductivity 1.05 W/m.C
> Density 2500 kg/m3
> Specific heat 750 kJ/kg.c
> Emissivity 0.84
> Solar absorptivity 0.27
> 
> and at the same time I can define the "optical property" for the above
> glass(traparent construction) through specifying one certain item from the
> "optical database". its optical property may be as follows:
> 
> ISO 6946 U values (horiz/upward/downward heat flow)=  5.630  6.774  4.595
> (partition)  3.737
> Direct transmission @ 0, 40, 55, 70, 80 deg
>    0.230 0.224 0.212 0.172 0.104
>  Layer| absorption @ 0, 40, 55, 70, 80 deg
>     1  0.329 0.358 0.381 0.388 0.358
> 
> My questons are,
> (1)	For Solar Absorptivity(0.27 here) and absorption of 5
> angles(0.329,0.358,0.381,0.388,0.358 here), which one is used in the
> calculation?
> (2)What relationship exists between Solar Absorptivity and "absorption of
> 5 angles"?
> 
> I tried again and again, and I find that the simulation result will not
> change if only either of the above two is changed. The simulation result
> will change if both of them are changed.
> 
> Any answers are welcomed.
> 
> Thank you in advance.
> 
> Regards,
> 
> Qiu
> 
> 
> 
> 
> 
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