Re: [TRNSYS-users] Type 56 - strange window U-value

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

Gilles,
  If I understand correctly, Type56 calculates the window U-value at
each time step and at each iteration in the simulation. The u-value at
any point in time is dependent upon a complex calculation of window pane
temperatures, gas cavity temperatures, zone temperature, and ambient
temperature. The u-value reported in the WindowLib is at some reference
condition and is for the center of glass. There is a Type56 output (NTYPE
50 among the "surface outputs") available to show what value
Type56 is calculating for the window u-value during the simulation.
Cheers,
 David


At 07:55 10/12/2006, Gilles Fraisse wrote:
> dear trnsys users ,
> using TYPE 56, we have some problems with the U value of the window. For
> exemple, I use this window from the german library (window type, library
> ...) :
>
> Unit System : SI, Name : TRNSYS 15 WINDOW LIB, Desc :
> Waermeschutzglas,Ar, 1.3 71/59, Window ID : 2002, Tilt : 90.0
> Glazings : 2, Frame : 11 2.270, Spacer : 1 Class1 2.330 -0.010 0.138,
> Total Height: 1219.2 mm, Total Width : 914.4 mm
> Glass Height: 1079.5 mm, Glass Width : 774.7 mm
>
>
> In the *.bui file , I consider an area of 4.15m² . But which value of U
> (and of area) is really used in the simulation ? I have compared with the
> steady state modelling (constant external temperature - solar radiation
> =0, constant internal heat gain ... ) and I cannot find 1.3 W/m²K , nor
> 0.85*1.3 + 0.15*8.17/3.6 (If I consider the frame). And there's no
> problem if I delete the window.  
>
> Has anybody carried-out the same steady state checking  with one
> window ?
>
> best regards
> G. Fraisse
>
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