[TRNSYS-users] Type56 - 2 active layers in one wall??

[Jeff Thornton]

> I'm trying to simulate a two-storied house with floor heating and
> chilled ceiling. This means I need two active layers in the first level
> floor. This isn't permitted by Trnbuild. Does anyone have an idea how to
> get around this limitation?

Bjorn, TRNSYS users and developers,

We're just finishing up a study for one of the U.S. National Energy
Laboratories on modeling radiant floors in TRNSYS and we've found some
interesting things.  We compared the active layers in Type 56 with a very
detailed 3-d radiant floor model that we wrote (somewhat slow to run) and
also with a simplified radiant floor model that only takes a few
parameters (a newer version of our Type 653 approach).  I've attached a
plot of the results to this e-mail and you can see for yourself how well
the models match up.

This provides us with the following benefits:

1) The Type 56 active layers, while somewhat limited in scope due to the
correlations they are based on, does a really nice job of matching the
very detailed radiant slab model.  This fact gives us greatly increased
confidence in the active layers in Type 56!

2) By specifying all of the detailed design information (number of pipes,
pipe sizes, pipe properties etc.), the detailed radiant slab model can be
used to generate the information required by the simple model
(effectiveness).  The detailed model is also not constrained by the pipe
spacing, number of pipes restrictions that the active layers in 56
require.

3) The simple radiant floor model, which runs extremely quickly, can be
connected to simple zone models (air temperature from zone model to slab
model, heat transfer to zone from slab model to zone model) and also to
the detailed Type 56 building model (by creating thin, highly conductive
layers in Type 56 and connecting the surface temperatures between the
models).  This surface-to-surface approach can also be used to model many
of the unique walls and floors that have been developed (phase change
walls etc.)

4) Multiple radiant floor models can be connected to Type 56 in this way. 
We also have a version that allows the user to have both a radiant floor
heating the zone above and a cooled ceiling cooling the zone below without
having to "fake" a zone between the two piping networks.

5) Either of the new radiant slab models can be connected to our "IEA
reference standard" 3-d ground heat transfer models to account for the
long term heat build-up in the soil under the zones.

6) If you don't have detailed design information, the simple model can be
exercised to determine the effectiveness of the slab that is required to
meet the loads.  The user could then go back to the detailed model and
investigate the required number of pipes, spacing, etc. until the desired
effectiveness is reached.

We're in the process of writing up our findings and creating a tutorial
for using the radiant slab models in TRNSYS.  We'll also be working
closely with TRANSSOLAR and the rest of the TRNSYS development group to
better integrate our models with the powerful Type 56 model.  The new
models are available for purchase and we're working on the documentation
set for inclusion in the next release of our libraries (v3.0).

Have a great week!

Jeff


Jeff Thornton
President - TESS, LLC

2916 Marketplace Drive - Suite 104
Madison WI 53719 USA

Phone: 608-274-2577
Fax: 608-278-1475
E-mail: thornton at tess-inc.com
Web: www.tess-inc.com
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