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

[David Bradley]

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.
>
>
>_______________________________________________
>TRNSYS-users mailing list
>TRNSYS-users at engr.wisc.edu
>https://www.cae.wisc.edu/mailman/listinfo/trnsys-users

****************************************************************************************
Thermal Energy System Specialists (TESS), LLC
David BRADLEY                           2916 Marketplace Drive - Suite 104
Partner                                        Madison, WI 53719
Phone: (608) 274-2577 USA
Fax: (608) 278-1475
E-mail: bradley at tess-inc.com
Web Pages:  http://www.tess-inc.com     and      http://www.trnsys.com

"Providing software solutions for today's energy engineering projects"
****************************************************************************************
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.onebuilding.org/pipermail/trnsys-users-onebuilding.org/attachments/20070515/2b24668f/attachment-0005.htm>