Modelling perimeter thermal bridges at a slab wall connection

[Carlos Acuna]

Hello from Perth, Australia,

I am a new user of THERM.  I am very comfortable modelling walls and concrete slabs and calculating psi-values for wall corners.  

I am now trying to calculate the psi-value of the perimeter thermal bridge between a ground-coupled concrete slab and the timber frame wall.

I am trying to figure out how to define the boundary condition at the bottom of the ground object.  Because ground temperature is relatively constant by the time you get to 3 meters depth, I modelled the ground object 3 meters deep. I assigned a boundary condition with a temperature of 14 degrees C and an Hc coefficient of 1000 w/m2.K.

Am I on the right track?  Are there any good tutorials or YouTube videos you could refer me to?

Thanks for your assistance!

Carlos

[Daniel Bettenhausen]

Since Therm does not allow temperature to be constrained at the boundary employing a very high heat transfer coefficient will achieve the same result.  The sensitivity of the result to the prescription of temperature at that boundary could be evaluated by increasing the depth of the solution domain and comparing the outcomes. 

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[archi...@gmail.com]

Hi Carlos,

Look at this old tred.
It should help you about the geometric and BC conditions that EN ISO 10211 and EN ISO 13370 set for calculations involving ground based details

https://groups.google.com/g/lbnl-therm/c/wDGqqkgTBAw/m/S1LbMpH33gYJ

Ciao

Fabrizio

[archi...@gmail.com]

By the way.
The green BC you underlined in red should be adiabatic and the model of the ground should have larger horizontal and vertical dimensions. (See EN ISO 10211).

Ciao

F.