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[EnergyPlus_Support] Re: Ground heat transfer from an uninsulated floor of an unconditioned sunspace
The slab program takes monthly average space temperatures as input. This includes both day and night. It then calculates the slab inside and more importantly underside surface boundary temps. As Ned said solar is not as such reflected on this monthly average surface temp directly. You then use the "otherside" objects in e+ to assign the outside boundary surface temp to that boundary for you normal run idf. This was all in the docs and examples. I had pretty good results.
The infalling solar won't change the underside boundry temperature. However, you may want to play with the reflection index of your floor to assume a better distribution if you are using "fullExterior(withreflections)" as the full infalling solar falls on the floor in this mode.
Jean
--- In EnergyPlus_Support@xxxxxxxxxxxxxxx, "Edward G. Lyon" <eglyon@...> wrote:
>
> My most recent analysis was an unconditioned building with lots of solar gain. I tried iterating slab with calculated space temperatures, but it would not match my measured conditions during the summer. I could only match measured summer conditions by manually inputting under slab temperature values. I think a hint about the issue is that slab works with the space temperature but does not concern itself with solar gain. Slab probably works fine for a dark basement.
>
> Ned Lyon, P.E. (MA, WV)
> Staff Consultant
> SIMPSON GUMPERTZ & HEGER
> 781.907.9000 main
> 781.907.9350 direct
> 781.907.9009 fax
> www.sgh.com
>
> From: EnergyPlus_Support@xxxxxxxxxxxxxxx [mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx] On Behalf Of FrancescoP
> Sent: Tuesday, June 04, 2013 12:49 PM
> To: EnergyPlus_Support@xxxxxxxxxxxxxxx
> Subject: [EnergyPlus_Support] Re: Ground heat transfer from an uninsulated floor of an unconditioned sunspace
>
>
>
> I add that I'm considering F. Droulia et al (2009) "Ground temperature estimations using simplified analytical and semi-empirical approaches" and other methods in order to estimate the ground temperature to use in the object Site:GroundTemperature:BuildingSurface
>
> --- In EnergyPlus_Support@xxxxxxxxxxxxxxx<mailto:EnergyPlus_Support%40yahoogroups.com>, "FrancescoP" <fpasserini.tn@<mailto:fpasserini.tn@>> wrote:
> >
> > I'm modelling an unconditioned sunspace. The floor is not insulated: it is made by 10 cm concrete and then there is the ground. The adjacent building is unconditioned too. It is situated in an Alpine region in Northern Italy. I have to validate the model through a comparison between the output data of the simulation and the monitored data.
> > I wondering whether using the "slab pre-processor" would be the best solution. In fact, in the model of the "slab pre-processor" the internal temperature has a sinusoidal hourly variation while in my case the internal temperature changes quickly and irregularly and because of the solar radiation the temperature inside the sunspace is often very different than the outdoor air.
> > I think that an alternative solution could be modelling the floor considering not only the concrete, but also a depth of the ground. I have calculated the thermal trasmittance through the ground between sunspace and external environment with a FEM software, then I have createe a construction with 10cm concrete + ground (50cm ?) + "virtual layer" in order to match the calculated U-value. On the bottom side of the construction, in the field "Outside Boundary Condition" of the object BuildingSurface:Detailed relative to the floor, I'm trying using both using "Outside" and using "Ground" but I see only a small difference, probably because of the great thickness of the ground layer.
> > Any suggestion, please? Should I use the "slab pre-processor"?
> > Moreover, I think the problems that I have with the validation concern also the distribution of solar radiation, but for this message I think I have written enough :-)
> > Regards
> > Francesco Passerini
> >
>
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