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Re: [EnergyPlus_Support] Making the Radiant Floor more realistic

To: EnergyPlus_Support@xxxxxxxxxxxxxxx
Subject: Re: [EnergyPlus_Support] Making the Radiant Floor more realistic
From: "Michael J. Witte" <mjwitte@xxxxxxxx>
Date: Wed, 29 Nov 2006 16:55:27 -0600
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Several options are available to account for portions of the floor covered by 
merchandise in order to reduce the radiant :

1.  Divide the floor into two (or more) parts.  For the area that is covered by 
merchandise, add one or more layers to the construction to represent the 
merchandise and place the source layer below these.  Because the merchandise 
layer will be rather thick, this may cause some CTF computation problems, but 
it may work OK.  Link the surfaces together using "RADIANT SYSTEM SURFACE 
GROUP" and then reference the group name in the LOW TEMP RADIANT 
SYSTEM:HYDRONIC object.

2.  Divide the floor into two (or more) parts and reduce the thermal 
absorptance for one part.  Again, use the surface group approach.

3.  Add internal mass or additional interior surfaces to reduce the view 
factors from the floor to the roof.

Mike


On 27 Nov 2006 at 18:35, Ian Doebber wrote:

> From a realistic standpoint, I believe that the floor/ceiling radiative
> transfer is too large for a radiant floor.  With a completely empty retail
> space, it makes sense, yet with ~40% of the floor covered by merchandise etc,
> I'd like to figure out a way to decrease the radiative exchange therefore
> decreasing the capacity of the radiant floor.  
> 
>  
> 
> For example, comparing with a baseline all air/passive floor system, the floor
> temperature is just under the setpoint temperature ~75 F while the interior
> roof temperature reaches ~83 F during the Las Vegas design day (exterior roof
> temperature ~170 F) which seems realistic.  With just a radiant floor of ~70 F
> the interior roof temperature is ~75 F which does not seem reasonable.  
> 
>  
> 
> How can I decrease the radiative exchange.  I've decreased the thermal
> absorptivity of the interior ceiling from 0.9 to 0.01 which did have somewhat
> of a change but surprisingly not much.  I don't want decrease the floor
> absorptivity because the thermal connection between the skylights and the
> floor.
> 
>  
> 
> This is important for two reasons.  First, getting a greater understanding of
> the space air/surface temperatures for determining thermal comfort.  Second,
> understanding what the change in the radiant floor capacity and therefore
> impact on the plant system.
> 
>  
> 
> Thanks in advance
> 
>  
> 
> Ian Doebber
> 
> Arup
> 
>  
> 
>  
> 
> ________________________________
> 
> From: EnergyPlus_Support@xxxxxxxxxxxxxxx
> [mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx] On Behalf Of Michael J. Witte
> Sent: Wednesday, October 25, 2006 7:45 AM
> To: EnergyPlus_Support@xxxxxxxxxxxxxxx
> Subject: RE: [EnergyPlus_Support] Further Insight : Skylight / Radiant Cooling
> Strange Behavior
> 
>  
> 
> We have confirmed that this is a reporting error just for the zone level
> window 
> heat gain/loss report variables. When radiant cooling is active, the zone 
> surface heat balance is called extra times to update the surface temperatures.
> The accumulation of Zone Window Heat Gain/Loss was not being reset to zero 
> within this loop. This will be fixed for the next release. Until then the 
> workaround is to use the surface-level Window Heat Gain/Loss report variables
> when using radiant heating/cooling systems.
> 
> Mike
> 
> On 23 Oct 2006 at 22:29, Michael J. Witte wrote:
> 
> > Digging into this further, the problem appears to be the values reported by
> > "Zone Window Heat Gain" and "Zone Window Heat Gain Energy". When the
> radiant
> > cooling is active, these zone variables do not agree with the surface
> > variables 
> > "Window Heat Gain" and "Window Heat Gain Energy". So, use the surface 
> > variables instead and I think you will find the results to be more
> > reasonable.
> > 
> > Checking the change in cooling load with and without the skylights, at hour
> > 10:00:
> > 
> > Zone Window Heat Gain = 5.53E+04
> > Window Heat Gain = 1.38E+04
> > Change in cooling load w/o skylights = 5.89E+03
> > 
> > So, this appears to be a reporting problem with the zone level window heat
> > gain 
> > report variable and not a problem in the overall heat balance.
> > 
> > Mike
> > 
> > 
> > Mike
> > 
> > 
> > On 19 Oct 2006 at 13:37, Michael J. Witte wrote:
> > 
> > > Ian: 
> > > 
> > > If you delete the skylights, does the cooling load on the radiant system
> > > change 
> > > by the same order of magnitude as the reported heat gain from the
> skylights?
> > > I 
> > > suspect this may just be a problem with the reported window heat gain
> > rather
> > > than a real heat balance problem. The reported window heat gain is just
> a
> > > side 
> > > calculation for reporting purposes, that value is not actually used in
> the
> > > heat 
> > > balance.
> > > 
> > > Mike
> > > 
> > > 
> > > On 15 Oct 2006 at 15:42, Linda Lawrie wrote:
> > > 
> > > > At 04:27 PM 10/13/2006, Griffith, Brent wrote:
> > > > >I believe this is a known bug (CR6897). But unfortunately it isn't a
> > > > >quick job and I don't think it was fixed in V1.4 (which is already
> > out).
> > > > 
> > > > As Brent says, this is a known or suspected problem. If you submit 
> > > > your file (either send direct to me or upload to the support web 
> > > > site), it may help our developer in tracking it down.
> > > > 
> > > > 
> > > > Linda
> > > > 
> > > > EnergyPlus WebSite: http://www.energyplus.gov
> <http://www.energyplus.gov> 
> > > > Owner: EnergyPlus_Support list
> > > > Member: EnergyPlus Development Team
> > > > 
> > > > 
> > > > 
> > > > [Non-text portions of this message have been removed]
> > > > 
> > > > 
> > > > 
> > > > The primary EnergyPlus web site is found at:
> > > > http://www.energyplus.gov <http://www.energyplus.gov> 
> > > > 
> > > > The group web site is:
> > > > http://groups.yahoo.com/group/EnergyPlus_Support/
> <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 <mailto:EnergyPlus-Support%40gard.com> 
> > > 
> > > 
> > > 
> > > 
> > > 
> > > The primary EnergyPlus web site is found at:
> > > http://www.energyplus.gov <http://www.energyplus.gov> 
> > > 
> > > The group web site is:
> > > http://groups.yahoo.com/group/EnergyPlus_Support/
> <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 <mailto:EnergyPlus-Support%40gard.com> 
> > 
> > 
> > 
> > 
> > 
> > The primary EnergyPlus web site is found at:
> > http://www.energyplus.gov <http://www.energyplus.gov> 
> > 
> > The group web site is:
> > http://groups.yahoo.com/group/EnergyPlus_Support/
> <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
> > 
> > 
> > 
> > 
> > 
> > 
> 
>  
> 
> ____________________________________________________________
> Electronic mail messages entering and leaving Arup  business
> systems are scanned for acceptability of content and viruses
> 
> 
> [Non-text portions of this message have been removed]
> 
> 
> 
> 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





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References:
- [EnergyPlus_Support] Making the Radiant Floor more realistic
  - From: Ian Doebber

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