Mold Simulator – Tutorial 4
Calculation of linear thermal transmittance of wall/floor junction
In this tutorial we'll examine the following thermal bridge and compute linear thermal transmittance following the method described in EN ISO 10211 at chapter 10.4:
W:
wall
F: floor
G: ground
First we need to correct ground size and place adiabatic areas. As stated in EN ISO 10211:
floor width must be the minimum between 4m and 0.5 x B', where B' is the characteristic dimension of the floor (11m in this case);
ground width outside the building and depth below ground level must be the minimum between 2.5 x B' and 20m.
Following these criteria we'll obtain:
Green
areas are adiabatic
Before proceeding with linear thermal transmittance computation, we need to determine floor's transmittance. In order to determine it we'll apply Option B decribed at EN ISO 10211 10.4.3; we need to perform a simulation with the following configuration:
Please
note that wall portion above the the ground level has been filled
with adiabatic material and wall portion below ground level has been
filled with ground material. In folder “Doc/samples/mold_simulator”
you'll find a file named example10_floor.mos; this
contains the floor simulation:
In order to get the correct transmittance value for the floor you must go to “Simulation” tab, “Flows” (on the right of “Simulation settings”, at the bottom) and:
uncheck “Auto width detection”;
set “Def. Width (U)“ to 4000mm;
resimulate.
Now
we know that floor's transmittance is 0.2387 W/m²K. Please open
example10.mos (in folder “Doc/samples/mold_simulator”),
which is the wall/floor junction with all the proper materials
applied. As you can see in “Elements” tab (pressing
button and clicking on elements):
wall's element has automatic U detection activated;
floor's element has automatic U detection disabled and U set to 0.2387 W/m²K.
Everything is set to obtain linear thermal transmittance; simply go to “Simulation” tab. One final note: floor boundary condition's surface resistance is 0.171 (since flow direction is downward) and internal wall boundary condition's surface resistance is 0.131 (since flow direction is horizontal).