[Bldg-sim] FEA heat-transfer analysis of envelope designs

[D. Charlie Curcija]

Somebody already pointed out, but to clarify, THERM program does excellent
job at modeling 2-D heat transfer in building envelopes.  It was originally
developed for modeling fenestration systems (windows, doors, etc.), but it
can be used for any other façade element, since they are generally simpler
than intricate details of window frames.  The benefits of using THERM are
numerous, but to cite few most important ones:

 

-          Free with simple registration (don’t be fooled by the fact that
it is free to the public, because substantial funding went into its
development by US DOE)

-          Has automated mesher and error estimator/mesh refinement with no
user intervention (fully automated quality mesh generation)

-          Has powerful drawing capabilities and import from dxf and scanned
drawings

-          Has extensive library of building materials (users can add their
own, but the built in library is impressive)

-          Has built in correlations for convective heat transfer in
building cavities

-          Has library of default boundary conditions appropriate for
buildings (user can add their own too)

-          In addition to 2-D conduction heat transfer model, has detailed
radiation model using grey body radiation enclosure algorithms for both
cavitie4s and indoor/outdoor boundaries

-          Calculates U-factors based on indoor-outdoor temperature
difference.

-          Has powerful output capabilities (color flooded plots of
temperatures, heat fluxes, mesh display among other things)

 

Charlie

DesignBuilder Software

 

From: bldg-sim-bounces at lists.onebuilding.org
[mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Scott Schuetter
Sent: Tuesday, January 19, 2010 3:04 PM
To: Josh K
Cc: bldg-sim at lists.onebuilding.org
Subject: Re: [Bldg-sim] FEA heat-transfer analysis of envelope designs

 

Josh,

 

I don’t have any experience with Elmer or GiD, but I do have some experience
with ANSYS. When we ran into parts with large aspect ratios, we would try
and use 2-D or 1-D elements. The drywall and studs will predominantly
conduct heat in one direction anyways. You can check this with a quick Biot
number calculation. So, if GiD has these type of elements available I would
try using them in concert with your 3-D elements.

Scott Schuetter
Energy Center of Wisconsin
PH: 608-238-8276 x149
FX: 608-238-0523 

  _____  

From: Josh K [mailto:jeemang at gmail.com] 
Sent: Monday, January 18, 2010 5:53 PM
To: bldg-sim at lists.onebuilding.org
Subject: [Bldg-sim] FEA heat-transfer analysis of envelope designs

 

Hi all;

I'm interested in using FEA to model the heat-transfer characteristics of
several building envelope designs. I'm attempting to use Elmer
(http://www.csc.fi/english/pages/elmer) to do this. Because Elmer doesn't do
anything more than very simple mesh creation, I'm using GiD
(http://gid.cimne.upc.es/) to attempt to mesh my wall section.

However, I'm having some serious problems creating a mesh. I'm not overly
experienced in mesh creation, but I have a feeling this stems from the
ridiculous aspect ratio of several parts of the assembly (ie, a 11' x 6' x
5/8" sheet of drywall) and the relatively minuscule thickness (~1/16") of
the steel studs and z-girts that are in the construction.

I'm wondering if anyone has conducted any such analysis before and could
offer some meshing tips. Alternatively, can anyone recommend a resource I
could consult?

Many thanks,

Josh

-- 
Josh Kjenner, P.Eng., LEED AP
Manasc Isaac Architects Ltd.
10225 100 Avenue :: Edmonton, AB T5J 0A1
780.429.3977

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