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

[David Bradley]

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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