[EnergyPlus_Support] Re: Solar distribution in a double skin facade against simple skin results

["aymericnovel" <nanabush@xxxxxxxxxx>]

Hi,

I am not sure if I am right but I am having a doubt about a particular output reporting in Eplus. Still working on my double skin facade project, I am now facing a fact: 

When I sum the diffuse solar gains from each interior windows using "Initial Transmitted Diffuse Solar Transmitted out through Inside of Window Surface" for a zone (I did separate heat fluxes going in and out the zone so I don't count heat going out of that zone, just that one coming in), I don't find the same amount provided by "Zone Diff Solar From Interior Windows"...

Even if I substract the heat flux going out of the zone through these windows I still have a total amount far superior than that of "Zone Diff Solar From Interior Windows"

Any thought about that?

Thanks a million
Aymeric

--- In EnergyPlus_Support@xxxxxxxxxxxxxxx, "aymericnovel" <nanabush@...> wrote:
>
> Hi,
> 
> EnergyPlus uses angular properties for beam transmitted solar to correct the solar transmission coefficient the user inputs. Does that apply also to the interior window that does a beam-to-diffuse transmission? It should but I can't see that in my outputs...
> 
> 
> thanks for the help!
> Aymeric
> 
> --- In EnergyPlus_Support@xxxxxxxxxxxxxxx, ppeixeiro@ wrote:
> >
> > Your interior window is defined two times: once in each zone they
> > seperate. It might be the case that you're reporting "Beam Solar
> > transmitted through interior window" for the inteiror window on the
> > surface of the DSF zone, and it should be the window that is located the
> > surface of the main zone.
> > 
> > 
> > > Pedro,
> > >
> > > In regards with the transmission of solar energy through the double skin,
> > > I have a question:
> > >
> > > In the results, we can see that the output variables at the building
> > > central zone level (the zone supposedly protected by the DS system)are
> > > generated, say you have about 20kW of Zone beam solar from interior
> > > windows and 40kW of Zone diffuse solar from interior windows.
> > > It is weird that I have a 0 value for the interior window level ouput
> > > "Beam Solar transmitted through interior window" I don't quite understand
> > > that...
> > > Because of that I am not sure anymore how E+ handles the solar in and out
> > > the zone and the cavity.
> > > I am not sure if the big difference I was talking about in my first
> > > message was not due to the fact that only the diffuse part is well treated
> > > here...What do you think?
> > > Because the impact of the cavity airflow is clearly on the glazing net
> > > gains which makes sense since it cools down the structure that was partly
> > > charged with solar heat, hence one can say it takes away part of the sun
> > > heat (although I still think it is small).
> > >
> > > Aymeric
> > >
> > > --- In EnergyPlus_Support@xxxxxxxxxxxxxxx, Pedro Peixeiro <ppeixeiro@>
> > > wrote:
> > >>
> > >> Hi Aymeric
> > >>
> > >> SHGC is the amount of solar radiation that enters a room both directly
> > >> transmitted through the facade and the fraction of radiation that its
> > >> absorbed by the facade and then transmitted into the room by both
> > >> convection and radiation heat transfer. In the pressence of a DSF, there
> > >> is a certain amount of heat transfer occurring inside the cavity (heat
> > >> removed by the air flow). This amount is not stationary, because it
> > >> depends on wind incidence, wind velocity, temperature difference between
> > >> cavity air and outside air, and surface temperature of the panes.
> > >> Because of this un-steady state heat flow, its not possible to establish
> > >> a convectional SHGC value for a DSF. Also, in reality, the heat flow
> > >> also varies with the height of cavity (temperature inside the cavity
> > >> increases with height) and so will heat transfer through the inside
> > >> pane. So it basically means we would get a difference SHGC value in
> > >> function of height, which complicates even more a definition of a single
> > >> SHGC value for a facade.
> > >>
> > >> Pedro
> > >>
> > >> On 01-04-2011 11:43, aymericnovel wrote:
> > >> >
> > >> > Dear all,
> > >> >
> > >> > I am studying a double skin facade design. I want to compare with a
> > >> > design using a simple skin with windows that have a SHGC of 0.25
> > >> > because it is the assembly SHGC I have to reach according to the local
> > >> > chinese standard. See the architect have asked me to justify the cost
> > >> > of using the external skin...good question when you think about it!
> > >> >
> > >> > So I have chosen inner skin and outer skin glazings so that it is
> > >> > equivalent first with a simple approximation of SHGCin x SHGCout =
> > >> > 0.25 . I know it is too simple but still it should not be too
> > >> > different in the zone inside the building.
> > >> >
> > >> > I am having trouble understanding the following fact:
> > >> >
> > >> > Having a combined SHGC of the inner and outer skin very close to the
> > >> > simple skin I try to compare with, I do not obtain at all the same
> > >> > amount of sun in the zone inside the building. Why? Normally the sum
> > >> > of the direct and diffuse solar transmitted through the internal
> > >> > windows should be close to the one through the external window in the
> > >> > case of the simple skin no?
> > >> >
> > >> > I have the feeling I am totally missing something basic here but it's
> > >> > late and I don't see it.
> > >> >
> > >> > Your help is more than appreciated!
> > >> >
> > >> > Thanks
> > >> > Aymeric
> > >> >
> > >> >
> > >>
> > >
> > >
> > >
> >
>




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