[TRNSYS-users] units of thermal bridge in TRNSYS

[Marc Medrano <mmedrano@diei.udl.cat>]

Dear all,

I am new in the list and a beginner of TRNSYS.

I want to test the effect of a thermal bridge in a building and I am 
having doubts on how to introduce the thermal bridge values.

According to this previous emails:

************

Hi Nicola,

nicola wrote:

> > Dear all,
> > I'm modelling a wall wit a thermal bridge effect.
> > I found a bug in TRNBuilt :
> > 1. If I put the value of resistence equal to xxx (hmK/kJ) in the layer 
> > manager, the program create a wall with a U-value expressed in kJ/h 
> > m^2K and a resistence equal to xxx in hm^2k/kJ!!!
>  
Thanks for finding this bug. I think it is only a problem of displaying 
the units.  The resistance should be entered in h m^2K /kJ, and not h m 
K /kJ.  When you check on the 'Layer type manager', the resistance is 
shown in h m^2K /kJ.

> > 2. the u-value of a wall with thermal bridge effect is lower than the 
> > same wall without thermal bridge effect.
>  
The u-value displayed in the 'Wall type manager' is calculated by adding 
two reference heat transfer coefficients to the wall (7.7 and 25 W/m2 K).

Best regards,

Diego

************

There is a bug in the units of the thermal resistance. In the input 
window units are h-m-K/kJ (m-K/W in SI) and in the Layer type manager 
units change to h-m^2K/kJ (m^2K/W in SI), conserving the same input 
value! According to Diego, it should be h-m^2K/kJ (m^2K/W in SI) in both 
places.

But typical values for a thermal bridge are given as lineal 
transmitances (W/mK in SI) or its inverse, the  lineal resistances (mK/W 
in SI). If the expected input units in TRNSYS for the thermal bridge 
resistance are h-m^2K/kJ (m^2K/W in SI) , how do I convert the lineal 
transmitances values I have available (units kJ/h-m^2K (W/mK in SI)) 
into this expected resistance in TRNSYS in h-m^2K/kJ? Multiplying the 
lineal transmittance by the thermal bridge length (which is also an 
input value), dividing by the total area of that wall and doing the 
inverse? Or the units bug was actually in the layer type manager window 
and the expected  units for the thermal resistance are  the ones in the 
input window (h-m-K/kJ (m-K/W in SI))? I feel that the second is the 
correct, but I would like some expert to confirm.

Thank you in advance,

Regards,

Marc