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Re: [TRNSYS-users] Windows shading coefficients

Dear David,
 
thank's for your help on the shading coefficients...
 
I have two new questions for the TRNSYS users:
 
1) In my project there are two adjacent buildings but the contact is not direct (air gap of 30 cm) so I need to define a radiation to 2 wall which are always shaded. In PREBID (or TRNBuild) there aren't shading coefficient to reduce the direct solar radiation for the wall (as for the windows), so I think is necessary to modify the radiation in IISiBat (or TRNSYS Studio).
Type 68 (Shading Masks) seems the correct tool, but I need a external file with the angular obstruction data. Maybe I can use type 34 (Overhang and Wingwall shading) in which the dimensions of the obstruction are set to a very high value. Is it exact? Do simpler ways exist to proceed?
 
2) Last week I have tried to transfer my old Trnsys 15 projects in Trnsys 16. I have a problem with type 16e (Radiation processor) when I try to calculate beam and diffuse radiation for a vertical surface with azimut among 225 (NE) and 315 (SE). The simulation is annual but stop with warnings and error at time 994 with the following notice:
 
TRNSYS Message 450: The maximum number of warnings allowed per simulation has been exceeded. Please fix these warnings or increase the limti on the number of warnings allowed per simulazion (LIMITS command)
 
The same climatic data return the expected results when I use TRNSYS 15's radiator processor. Non running project is attached.
 
Thank's in advance,
 
Eng. Maurizio Sorce
Department of Energy and Environmental Research (DREAM)
Università degli Studi di Palermo
(+39) 3495386296
----- Original Message -----
Sent: Monday, November 15, 2004 5:06 PM
Subject: Re: [TRNSYS-users] Windows shading coefficients

Dear Maurizio

1) I'm currently modelling in PREBID a residential building for which the montly Shading Coefficients on the windows have been calculated with the software ECOTECT. I insert the SC in the appropriate field ("external shading coefficient") as an input and set the "view factor" to 0,5 (vertical surfaces). It's the exact way? My doubt is that the solar incident radiation is halved (view factor = 0,5) and then reduced of the SC...

It is correct, provided that the shading coefficient from Ecotect is the opaque fraction of the window (i.e. 1 = completely shaded).
The view factor to the sky (FSky) is only used for longwave radiation so it will not interfere with shading.

The one thing to bear in mind about PREBID's external and internal shading coefficient is that the entered fraction effects both beam and diffuse radiation equally. Thus if you enter a value of 0.5 for the external shading factor, half of the incident diffuse radiation and half of the incident beam radiation will enter the space. If you want to treat beam and diffuse radiation separately, you can use one of the external shading models (Type34, or Type68).

2) It's possible to use old TESS libraries with TRNSYS 16 or are they already comprised in the new version?

Because of the change in coding standards for components between version 15 and 16, the TESS Libraries v. 1.x are not directly useable with TRNSYS v 16. We have, however, expanded the libraries and released version 2.0, which are not only compatible with TRNSYS 16 but are also backwards compatible with TRNSYS 15. If you are interested in upgrading, you will be credited the full amount that you paid for your version 1.x libraries toward the purchase of version 2.x libraries. If you do not wish to upgrade then you can follow the steps laid out in the TRNSYS 16 documentation that show you how to modify a TRNSYS 15 Type to make it accessible from TRNSYS 16. I will send along a second email containing a document that lists the contents of the 12 version 2.0 libraries as well as an order form that contains the pricing information. I would be happy to answer any questions that you might have about them.

Kind regards,
  David

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