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

On Thu, Aug 15, 2013 at 8:17 AM, ilikemyselfmore <ilikemyselfmore@xxxxxxxxx> 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