[EnergyPlus_Support] Re: Trying to explain temperature differences in a room with conduction

["ilikemyselfmore" <ilikemyselfmore@xxxxxxxxx>]

Thank you Niraj, Jeffrey's strategy works.

Sarah

--- In EnergyPlus_Support@xxxxxxxxxxxxxxx, Niraj Poudel <nirajpdl@...> wrote:
>
> Sarah,
> 
> In case you might have missed it. Since a new chain has formed in the
> support group for your query. Jeffrey has a really good strategy for you to
> test your model.
> 
> *From:* EnergyPlus_Support@xxxxxxxxxxxxxxx [mailto:
> EnergyPlus_Support@xxxxxxxxxxxxxxx] *On Behalf Of *Jeffrey Spitler
> *Sent:* Thursday, August 15, 2013 11:18 AM
> *To:* EnergyPlus_Support@xxxxxxxxxxxxxxx
> *Subject:* [EnergyPlus_Support] Re: Trying to explain temperature
> differences in a room with conduct****
> 
> ** **
> 
>  ****
> 
> Have you set the exterior surface thermal absorptances to zero or a small
> number like 0.001?  That will effectively turn off radiation exchange with
> the environment regardless of what the sky model is doing.****
> 
> Jeff Spitler
> 
> That sounds like a very simple and effective strategy!****
> 
> ** **
> 
> *James V Dirkes II, PE, BEMP, LEED AP**
> **www.buildingperformanceteam.com* <http://www.buildingperformanceteam.com/>
> *
> **Energy Analysis, Commissioning & Training Services**
> *1631 Acacia Drive, Grand Rapids, MI 49504 USA
> 616 450 8653****
> 
> ** **
> 
> 
> ****
> 
> 
> 
> 
> On Thu, Aug 15, 2013 at 10:06 AM, ilikemyselfmore <ilikemyselfmore@...
> > wrote:
> 
> > **
> >
> >
> > Niraj,
> >
> > I'll try to change the sky temperature in the .idf file, I didn't think of
> > that before. Thanks. I'll keep you posted.
> >
> > Attached is a copy of my .epw file if you want to have a look but I doubt
> > it will be interesting.
> >
> >
> > Sarah
> >
> > --- In EnergyPlus_Support@xxxxxxxxxxxxxxx, Niraj Poudel <nirajpdl@>
> > wrote:
> > >
> > > Sarah, could you attach your .epw file so we can have a look at it? I
> > think
> > > you might also have to change the sky temperature in your .idf file to
> > stay
> > > constant at a certain value to prevent the heat loss to the sky. If I
> > > remember correctly, the sky temperature defined in the .idf file takes
> > > precedence or overwrites horizontal infrared radiation. You might have to
> > > look into the documentation for the answer to that.
> > >
> > > Niraj
> > >
> > >
> > > On Thu, Aug 15, 2013 at 8:17 AM, ilikemyselfmore
> > > <ilikemyselfmore@>wrote:
> > >
> > > > **
> >
> > > >
> > > >
> > > > Thank you all for your answers.
> > > >
> > > > I did change the solar variables in the weather file. And I also
> > thought
> > > > about energy exchange with the sky, but I didn't find a way to reduce
> > its
> > > > effect. The value for the horizontal infrared radiation is already 0
> > in my
> > > > weather file. Do you have any other suggestions?
> > > >
> > > > Sarah
> > > >
> > > >
> > > > --- In EnergyPlus_Support@xxxxxxxxxxxxxxx, Niraj Poudel <nirajpdl@>
> > > > wrote:
> > > > >
> > > > > I totally agree with Jim. I had performed such a study about 2 years
> > ago
> > > > > when it was possible to set the convective coefficient of walls to
> > really
> > > > > minuscule values. Now, I dont think Eplus allows you to set such low
> > > > > convective coefficient values without generating a warning or error
> > of
> > > > > sorts.
> > > > >
> > > > > The radiant exchange with the sky during the night, on the other
> > hand, is
> > > > > considerably high and that explains the -5 oC temperature on the
> > roof.
> > > > If I
> > > > > remember correct the radiant exchange is tied to the infrared solar
> > > > > radiation (or the horizontal infrared radiation) data in the .epw
> > file.
> > > > > Manipulating that value could help your cause.
> > > > >
> > > > > Niraj
> > > > >
> > > > >
> > > > > On Wed, Aug 14, 2013 at 6:34 AM, Jim Dirkes <jim@
> > > > > > wrote:
> > > > >
> > > > > > **
> > > >
> > > > > >
> > > > > >
> > > > > > Oops. I missed the description "no wind and no sun on these
> > surfaces".
> > > > > > I'm not sure how you can model without sun unless you also changed
> > the
> > > > > > solar variables in the weather file, but I doubt you can model
> > without
> > > > > > radiant energy exchange to the sky.****
> > > > > >
> > > > > > ** **
> > > > > >
> > > > > > *James V Dirkes II, PE, BEMP, LEED AP**
> > > > > > **www.buildingperformanceteam.com*<
> > > > http://www.buildingperformanceteam.com/>
> > > > > > *
> > > > > > **Energy Analysis, Commissioning & Training Services**
> > > > > > *1631 Acacia Drive, Grand Rapids, MI 49504 USA
> > > > > > 616 450 8653****
> > > > > >
> > > > > > ** **
> > > > > >
> > > > > > *From:* EnergyPlus_Support@xxxxxxxxxxxxxxx [mailto:
> > > > > > EnergyPlus_Support@xxxxxxxxxxxxxxx] *On Behalf Of *Jim Dirkes
> > > > > > *Sent:* Wednesday, August 14, 2013 7:23 AM
> > > > > > *To:* EnergyPlus_Support@xxxxxxxxxxxxxxx
> > > > > > *Subject:* Re: [EnergyPlus_Support] Trying to explain temperature
> > > > > > differences in a room with conduction****
> > > > > >
> > > > > > ** **
> > > > > >
> > > > > > ****
> > > >
> > > > > >
> > > > > > And radiant energy exchange with the sky
> > > > > >
> > > > > > Jim Dirkes II ****
> > > > > >
> > > > > > Building Performance Team****
> > > > > >
> > > > > >
> > > > > > On Aug 14, 2013, at 7:10 AM, "ilikemyselfmore" <ilikemyselfmore@>
> > > > > > wrote:****
> > > > > >
> > > > > > ****
> > > >
> > > > > >
> > > > > > Dear Group,
> > > > > >
> > > > > > I am currently trying to simulate a room with no internal loads
> > > > (people,
> > > > > > lights and electric devices), no convection (no wind, no
> > ventilation
> > > > and
> > > > > > infiltration). I am trying to show only the conduction effects
> > through
> > > > the
> > > > > > walls, so I also tried to reduce the effects of the radiation.
> > > > > >
> > > > > > To make sure that my simulation would work, I created an EPW file
> > with
> > > > a
> > > > > > constant Dry Bulb Temperature at 5°C. Normally, the operative
> > > > temperature
> > > > > > in the room after a few weeks/months should also be 5°C. However,
> > after
> > > > > > running the simulation, I got 0.5°C in that room. All the 6
> > surfaces
> > > > are
> > > > > > made of 20cm thick concrete, and they are towards the outside.
> > There
> > > > is no
> > > > > > wind and no sun on these surfaces.
> > > > > > I observe that the roof outside surface is -5°C and that the floor
> > > > outside
> > > > > > surface is +5°C, but I am not sure how to explain these
> > differences.
> > > > Does
> > > > > > anyone have an idea?
> > > > > >
> > > > > > Thanks for you attention,
> > > > > >
> > > > > > Sarah****
> > > > > >
> > > > > > ****
> > > > > >
> > > > > >
> > > > > >
> > > > >
> > > > >
> > > > >
> > > > > --
> > > > > *Niraj Poudel, Architectural Engineer.*
> > > > > *PhD student, PDBE Program.*
> > > > > *Clemson University, Clemson, SC.*
> > > > > Linkedin: http://www.linkedin.com/pub/niraj-poudel/19/1ba/568
> > > > >
> > > >
> > > >
> > > >
> > >
> > >
> > >
> > > --
> > > *Niraj Poudel, Architectural Engineer.*
> > > *PhD student, PDBE Program.*
> > > *Clemson University, Clemson, SC.*
> > > Linkedin: http://www.linkedin.com/pub/niraj-poudel/19/1ba/568
> > >
> >
> >  
> >
> 
> 
> 
> -- 
> *Niraj Poudel, Architectural Engineer.*
> *PhD student, PDBE Program.*
> *Clemson University, Clemson, SC.*
> Linkedin: http://www.linkedin.com/pub/niraj-poudel/19/1ba/568
>




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