[TRNSYS-users] Windows shading coefficients

Tue Nov 30 07:01:26 PST 2004

Dear Michael and David,  

thanks for the useful suggestions. Now I am able to calculate the radiation
without problems.  
Mine last doubt concerns the insertion of the Windows Shading Coefficients.
Unlike PREBID, in TRNBuild it's not more possible to insert input as "external
Shading Coefficient", but only as "internal Shading Coefficient". Can I
also use these for the external obstructions? Obviously, as Michael suggests
in the case of walls, I could modify the radiations in TRNSYS Studio, but,
having to repeat the calculation for around hundred openings, this it would
make excessively complicated the model.

In TRNSYS 16 documentation miss the part regarding the mathematical description
of the components. Is it possible to download the complete manual from internet
or is it necessary to ask for it to the distributor?

Thanks again

Eng. Maurizio Sorce
Department of Energy and Environmental Research (DREAM)
Università degli Studi di Palermo
(+39) 3495386296

>-- Messaggio originale --
>From: Michaël Kummert <kummert at engr.wisc.edu>
>To: Trnsys Users <trnsys-users at engr.wisc.edu>
>Subject: Re: [TRNSYS-users] Windows shading coefficients
>Date: Mon, 29 Nov 2004 14:46:45 -0600
>
>
>Maurizio,
>>  
>> 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?
>
>You can define a special orientation for completely shaded external 
>walls and leave the corresponding radiation inputs unconnected (i.e. 
>constant to 0). For the sake of completeness, please note that this will
>
>not take into account longwave radiation heat exchange between the two

>walls (which I think is OK in your case). However, you should set their

>view factor to the sky to 0.0 since the walls will not have any longwave
>
>radiation exchange with the sky.
>
>> 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.
>
>The problem comes from the new definition of the simulation start time

>in TRNSYS 16: The start time is now really the time at the beginning of

>the simulation (not the time at the end of the first time step). TRNSYS

>16 components are called once (no iterations) during that initialization
>
>time step and they output their initial values.
>That change requires you to handle data files carefully: The first line

>of your data file corresponds to the average values between 00:00 and 
>01:00 on January 1st (or the instantaneous values at 01:00). The mode 
>you have chosen for Type 9 (mode 2) assumes that initial values ARE 
>provided so all values are shifted by one hour, hence the numerous 
>warnings that lead to the error message.
>You can easily fix the problems by adding a line at the top of the file

>for January 1st at 00:00, or by changing to mode 3 which assumes no 
>initial values are provided (using the Type9e proforma, "expert mode").

>Finally, you might want to use mode 5 or 6 (instead of 2 or 3) since 
>your file includes data for a full year. With modes 5 and 6 the 
>appropriate number of lines will be skipped in the data file if your 
>simulation does not cover a full year (remember to change the start day

>in Type 16!).
>
>Another error I noticed in your file: you have set the data reader to 
>interpolate values of solar radiation. Radiation values should never be

>interpolated in Type 9 (the solar radiation processor will interpolate

>them later). Also, you should pay attention to the "instantaneous or 
>average" parameters for each column in your file. Typically radiation 
>values are averages over the time step but temperature and humidity are

>instantaneous values at the hour.
>
>
>I hope this helps,
>
>Michaël Kummert
>
>PS. For those of you who might be worried, please note that all standard
>
>weather files are handled correctly by Type 89 and 109 in TRNSYS 16 
>without having to change any setting. You just have to worry about Type

>9 modes if you use custom files.
>
>
>-- 
>_________________________________________________________
>
>Michaël Kummert
>
>Solar Energy Laboratory - University of Wisconsin-Madison
>1303 Engr Res Bldg, 1500 Engineering Drive
>Madison, WI 53706
>
>Tel: +1 (608) 263-1589
>Fax: +1 (608) 262-8464
>E-mail: kummert at engr.wisc.edu
>
>SEL Web Site: http://sel.me.wisc.edu
>TRNSYS Web Site: http://sel.me.wisc.edu/trnsys
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