Re: [TRNSYS-users] "floor in direct contact with ground"

[David Bradley <bradley@tess-inc.com>]

Christophe, 
  Your translation is perfectly fine. Sometimes the effect is called
"ground coupling" as well. 

  To answer your question, the "standard" method is to
define a massless layer with a high thermal resistance underneath your
floor and connect it to either ambient temperature or some time varying
deep earth ground temperature. You might get such a temperature from the
Type77 Kasuda correlation. In some parts of the world, there are maps of
equivalent ground temperatures available just for this purpose.
Alternatively, there are a number of ground coupling models in the TESS
Ground Coupling library that you might use. These are a bit complicated
to implement but the idea of them is more physically correct than the
equivalent resistance method. In the Ground Coupling Library models, you
define a volume of soil underneath and around the floor. That volume of
soil is called the "near field" and is broken up into finite
elements that normally increase in size as they get farther from the
floor edge and bottom. Beyond the near field is a region called the far
field, which acts as an infinite thermal source / sink. When using a
ground coupling model with Type56, you define a boundary wall for your
floor and pass the inside surface temperature of the floor out of Type56
and to the ground coupling model. The ground coupling model solves the 3D
finite element conduction problem and calculates the temperature at the
outside boundary of the floor. This outside boundary temperature is
passed back to Type56 as an input. 

  We have had some good success with the model and have been working
with the developers of one of the International Energy Agency Tasks to
compare this model against an analytical solution and against other
models that have been created over the years. The 3D finite element
methodology seems to be uniquely flexible and shows quite good comparison
with the analytical solution. 
Kind regards,
 David



At 05:55 2/17/2006, Enertech wrote:
> Dear TRNSYS Users,
>  
> I would like to model a ?floor in direct contact with ground? (I don?t
> know the exact traduction for the french term ?plancher sur terre
> plein?). My goal is to estimate the interest of using the ground thermal
> capacitance, as a heat storage, in the global thermal capacitance of my
> building. 
>  
> My first idea was to define a boundary wall with the ground temperature
> for boundary. But in this case, I don?t use ground capacitance. My new
> idea is to introduce a layer in my wall (defined as an external wall)
> composed by 5 m of ground ? Do you think it?s a good way to take ground
> capacitance into account ?
>  
> Thanks for your answers,
> Christophe. 
>
> ===========================
> ENERTECH
> F-26160 FELINES SUR RIMANDOULE
> tel-fax : 04 75 90 18 54
> Email : sidler@club-internet.fr
> Web  :
>
> http://sidler.club.fr
> ================================ 
> _______________________________________________
> TRNSYS-users mailing list
> TRNSYS-users@engr.wisc.edu
> https://www.cae.wisc.edu/mailman/listinfo/trnsys-users

****************************************************************************************
Thermal Energy System Specialists (TESS), LLC
David BRADLEY                           2916 Marketplace Drive - Suite 104
Partner                                        Madison, WI 53719
Phone: (608) 274-2577 USA
Fax: (608) 278-1475
E-mail: bradley@tess-inc.com
Web Pages:  http://www.tess-inc.com     and      http://www.trnsys.com

"Providing software solutions for today's energy engineering projects"
****************************************************************************************