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Re: [EnergyPlus_Support] More on Core/Perimeter Temperatures
I was wrong yesterday. Actually, the slab program *can* model a fully
insulated slab. In the insulation object, use "under slab insulation" and set
the width so that the core area in the gtp output approaches zero.
Insulation,
2.0, !- RINS: R value of under slab insulation {m2-K/W}
3., !- DINS: Width of strip of under slab insulation {m}
Since the dimensions of the slab are not specified, rather the aspect ratio is
input, this is a 2-step process. Specify an insulation width on the order of
2m. Run slab. Check the core and preimeter areas reported in the gtp output
file. Change the insulation width to be 2m*(core+perimeter area/perimeter
area) and re-run. In the second run, the core are should be close to zero.
This represents a fully insulated slab case.
Mike
On 24 Apr 2006 at 16:47, Michael J. Witte wrote:
> > 2. Is there any way to consider a slab whose area is fully insulated?
> >
> > 3. How can I consider a slab made up o several material layers?
>
> The EnergyPlus slab preprocessor only allows one material layer for the slab.
> To model a fully insulated slab would required entering average thermal
> properties for the actual slab+insulation as the slab properties. This might
> not be a bad approximation, but it has some serious limitations.
>
> Mike
>
>
> On 21 Apr 2006 at 8:25, Jeff Haberl wrote:
>
> > Insulation is normally used around the perimeter because that is where the
> > largest Delta-T is experienced by the slab. A detailed analysis is
> complex,
> > involving soil properties, weather conditions, zone temps, surrounding
> > structures, and 2 or 3 dimensional heat transfer. There have been many
> studies
> > on this, two recent studies of note include the work by Moncef Krarti and
> Bill
> > Bahnfleth, both are documented in the ASHRAE literature. LBNL has also
> > published several simplified, yet accurate, reports on this as well by Joe
> > Huang and Fred Winklemann.
> >
> > We've watched soil temps under a habitat house for 5 years, and are still
> > learning more each time we look at the data. The center sensor follows the
> > thermostat, the sensor under the south side is influenced by solar
> radiation
> > on the exposed slab, the sensor on the north side behaves more like
> expected,
> > following the OA temp with a lag of 2 to 3 weeks.
> >
> > Jeff
> > BB 8=! 8=) :=) 8=) ;=) 8=) 8=( 8=) :=') 8=) 8=) 8=? BB
> >
> > Jeff S. Haberl, Ph.D.,
> P.E.............................jhaberl@xxxxxxxxxxxx
> >
> > Professor......................................................Office Ph:
> > 979-845-6507
> >
> > Department of Architecture.......................Lab Ph: 979-845-6065
> >
> > Energy Systems Laboratory.......................FAX: 979-862-2457
> >
> > Texas A&M University..............................77843-3581
> >
> > College Station, Texas, USA.......................URL: www-esl.tamu.edu
> >
> > BB 8=/ 8=) :=) 8=) ;=) 8=) 8=() 8=) 8=? 8=) 8=) 8= BB
> >
> >
> > -----Original Message-----
> > From: EnergyPlus_Support@xxxxxxxxxxxxxxx
> > To: EnergyPlus_Support@xxxxxxxxxxxxxxx
> > Sent: Thu Apr 20 17:42:31 2006
> > Subject: [EnergyPlus_Support] More on Core/Perimeter Temperatures
> >
> > Hi,
> >
> > 1. Could anyone explain to me why the physical model employed by the
> > slab calculation has insulation under the perimeter region, but not
> > under its core region? (At least this is what looks like from the
> > figure that comes along the guide).
> >
> > 2. Is there any way to consider a slab whose area is fully insulated?
> >
> > 3. How can I consider a slab made up o several material layers?
> >
> > Thanks a lot for your help,
> > jose
> >
> >
> >
> >
> >
> >
> >
> > The primary EnergyPlus web site is found at:
> > http://www.energyplus.gov
> >
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> > http://groups.yahoo.com/group/EnergyPlus_Support/
> >
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> >
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> the
> > "search" button.
> >
> > Yahoo! Groups Links
> >
> >
> >
> >
> >
> >
> >
> >
> > The primary EnergyPlus web site is found at:
> > http://www.energyplus.gov
> >
> > The group web site is:
> > http://groups.yahoo.com/group/EnergyPlus_Support/
> >
> > Attachments are not allowed -- please post any files to the appropriate
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> > in the Files area of the Support Web Site.
> >
> > EnergyPlus Documentation is searchable. Open EPlusMainMenu.idf and press
> the
> > "search" button.
> >
> > Yahoo! Groups Links
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> >
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> >
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> >
> >
> >
>
>
> ========================================================
> Michael J. Witte, GARD Analytics, Inc.
> EnergyPlus Testing and Support
> EnergyPlus-Support@xxxxxxxx
>
>
>
>
>
> The primary EnergyPlus web site is found at:
> http://www.energyplus.gov
>
> The group web site is:
> http://groups.yahoo.com/group/EnergyPlus_Support/
>
> Attachments are not allowed -- please post any files to the appropriate folder
> in the Files area of the Support Web Site.
>
> EnergyPlus Documentation is searchable. Open EPlusMainMenu.idf and press the
> "search" button.
>
> Yahoo! Groups Links
>
>
>
>
>
>
>
>
========================================================
Michael J. Witte, GARD Analytics, Inc.
EnergyPlus Testing and Support
EnergyPlus-Support@xxxxxxxx
The primary EnergyPlus web site is found at:
http://www.energyplus.gov
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http://groups.yahoo.com/group/EnergyPlus_Support/
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