[TRNSYS-users] us of Coldbridges

[Avesani Stefano]

Hi Pauline,

We are deeping the issue of thermal bridges in TRNSYS trying to find the best way of simulating this. What I am trying to simulate is a very simple zone with just one thermal bridge as transmitting external surface. Actually the QSENS calculated is coherent with the whole zone energy balance (of which the CBR “surface” is just one component and the other surfaces contribute to the energy balance even if they are set with BC identical). The heat flux lost through the CBR is then coherent with the formula q[W] = psi*l*deltaT.
What kind of zone have you used? Other surfaces? Which BC?

Looking forward to finding a good answer!
kind regards

Stefano



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From: trnsys-users-bounces at cae.wisc.edu<mailto:trnsys-users-bounces at cae.wisc.edu> [mailto:trnsys-users-bounces at cae.wisc.edu] On Behalf Of Pauline GELIN
Sent: Thursday, 19 September, 2013 13:35
To: David BRADLEY; trnsys-users (trnsys-users at cae.wisc.edu<mailto:trnsys-users at cae.wisc.edu>)
Subject: [TRNSYS-users] us of Coldbridges

Hi,

Sorry to multiply the questions but I I try to consolidate our simulations of buildings and another question remains about how the values of resistance and length for a coldbridge are used.

When I want to simulate a very simple building zone (one wall of 1m² with a U equals to 1W/m²K and one coldbridge of 1m with a U equals to 1W/mK) , with no weather data, a constant outside temperature of 19° and a constant inside temperature of 20°C, the QUA output (meaning static losses transmission) is well given as 2 W but the QSENS outputs isn’t (it seems to be equal to 6 W).
When I change lengths or resistance values, it always seems to have a factor of 5 between the input value of coldbridge and the output value of QSENS.
Could someone explain this to me?

Thank you very much for your help.

Best regards,

Pauline GELIN
Ingénieur Conception environnementale

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