Re: [TRNSYS-users] Tsky calculation with 2 different Types: Big difference in results!!!

[David Bradley <bradley@tess-inc.com>]

Talal,
  Type69 allows you to use two different sky temperature algorithms;
in one, the cloudiness factor is read as an input while in the other, it
is calculated internally based on ambient conditions (temperature,
humidity, and solar radiation). Type15 and Type69a use the same
algorithm. Type15 and Type69b do not. You can look at matched results
between Type15 and Type69a but unfortunately, you cannot use Type109 as
the weather component because it does not read, process, or output the
cloudiness factor. You need to use the combination of Types 89 and 16
instead. 

In looking at your project, I noticed a couple of other things as well.

First, and most importantly, when you change the units of an input, that
change only affects the value of unconnected inputs. As soon as you
connect the output of another component to the input, information is
passed directly and without conversion. It looks as though you changed
the input of Type33 to pascals so that you could directly pass the
atmospheric pressure output of Type109 (which is in pascals). You need to
leave the Type33 input units as atmospheres and you need to put an
equation into your input file to convert Type109's outputs from Pa to
atm.

Second, the elevation parameter in Type69 was set to 0 and should be set
to 240m as the elevation of Lyon. You can read the elevation from the
first line of the *.tm2 file.

Third, the wet bulb temperature calculated by Type15 and Type33 are
different because Type33 was set to "wet bulb calculation mode"
0 (do not calculate the wet bulb temperature).

Cheers,
 David


At 08:38 5/15/2007, Talal SALEM wrote:
> Dear fellows,
>  
> I have a question concerning the calculation of the effective Sky
> Temperature.
> When I use on the one hand the Type 15-6, and on the other hand a
> combination of Type 109 with the Type 69b and the Type33e, the results of
> the effective sky temperature differs although in the mathematical
> reference we can see that the same equations are used for both cases
> (Tsky in Type15-6, and Tsky in Type 33) in the calculation. [Please check
> attached Trnsys file]
> Can you please check this big difference (up to 10°c)?
> Thank you in advance
>  
> Talal S.
>  
>
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