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Re: [EnergyPlus_Support] Window5 data file
Rob.
OK, then it is not possible to use a window% datafile window with spectral data, correct? I have to build up a window with a construction of materials to refer to the WindowGlassSpectralData input object in the glass material definition, correct? That is the only reference I see to that object.
David
----- Original Message -----
From: Rob Hitchcock
To: EnergyPlus_Support@xxxxxxxxxxxxxxx
Sent: Friday, May 09, 2008 2:54 PM
Subject: Re: [EnergyPlus_Support] Window5 data file
David,
The SpectralDataFile named in the W5 report is only for human
reference. There is no link between EnergyPlus and the W5 database that
contains these spectral data. To use full spectral data within
EnergyPlus, you have to include these data in your IDF using the
WindowGlassSpectralData input object.
Rob
=======
David Scheer - L+U wrote:
> Rob.
>
> A couple of questions about how to get E+ to model spectrally
> selective glazing correctly:
>
> Can I assume that the "SpectralDataFile" named in the W5 EnergyPlus
> report data file (last column of each Layer# line) that can be
> referred to in the E+ ConstructionFromWindow5DataFile will cause the
> simulation refer to a
> WindowGlassSpectralData object with the same name? Can I also assume
> that if there is no object with that name that the tool defaults to
> SpectralAverage data?
>
> Or...to get spectral data into E+, do I have to create a glass
> material and a construction to refer a glass material layer to a
> WindowGlassSpectralData object?
>
> Thanks again,
> r3
>
> ----- Original Message -----
> From: Rob Hitchcock
> To: EnergyPlus_Support@xxxxxxxxxxxxxxx
> <mailto:EnergyPlus_Support%40yahoogroups.com>
> Sent: Tuesday, May 06, 2008 10:43 AM
> Subject: Re: [EnergyPlus_Support] Window5 data file
>
> David,
>
> See my comments interspersed below.
>
> Rob Hitchcock
> =======
> Results from experiments with window5 files, reversed layering for
> interior windows and low-E surface location:
>
> I was concerned with the idea of creating a reverse-layer low-E window
> subsurface for an adjacent window in an interior zone, since each glass
> material 'layer' actually has its own layers with different spectral
> qualities (back and front in the material definition). If the same
> materials are used for the reverse/rotated construction, front becomes
> back and back, front (outside to inside), and the lo-E surface ends up
> on the wrong side. Which zone should have the 'real' window definition?
> Am I thinking about this correctly?
>
> My guess is that a flipped-face, reverse-layer construction
> (double-negative, so actually a correct order of 1,2,3,4 surfaces) for
> the interior window of the outboard zone would yield the most 'correct'
> results, as this is the zone where the exterior conditions (surface
> temperature, diffuse solar) for the interior zone are determined (??).
>
> ROB - Yes, this is the correct approach if I understand your
> description. You want to reverse the order of the layers, and you want
> the coating to be on the correct face of its layer (i.e., it has to be
> flipped between the two window constructions).
>
> If this is correct, the hypothesis would be that because the lo-E
> coating is on #2 surface for the outboard zone, the Surface Inside
> Temperature of the interior window of the outboard zone should be warmer
> than if the layers were the 'wrong' way round. Also, there should be a
> higher deltaT between the inside and outside surface temperatures in a
> cooling situation.
>
> I built two pairs of window constructions, one normal (loE on #2
> surface) and one reversed (loE on #1 surface). The flipped material puts
> the loE coating on the correct face for the outboard zone, but not for
> the inboard zone, while the 'normal' material definition puts it on the
> correct face for the inboard zone (and is ALOT more intuitive), but not
> the outboard reversed-layer zone.
>
> ROB - You have to manually input the opposing surfaces rather than use
> the auto-generate capability of the UnenteredOtherZoneSurface input
> method.
>
> The hypothesis above proved out for this test. I'm still a bit
> uncomfortable with the results, which show about a 9% difference is
> resultant cooling loads (favoring the non-intuitive flipped-reversed
> construction) for a 70% glazed space inboard of a 100% glazed
> double-skin space. There is about 18% difference in Zone Diffuse Solar
> from Interior Windows (lower for the flipped-reversed material), which
> makes some sense, as the flipped version in W5 has an SHGC about 5%
> higher.
>
> ROB - Beware the Diffuse Solar report variables for Interior Windows.
> As of E+ v2.1 we changed the treatment of diffuse solar to address
> exactly the situation you are attempting to model. Try comparing values
> for "Initial Transmitted Diffuse Solar Transmitted out through Inside of
> Window Surface", described in the I/O Ref.
>
> One question is, what is used to determine inside surface temperature of
> the glass in the interior zone, and therefore convection and resultant
> air heat gains? Is it the exterior temperature of the outboard zone
> surface? Effective Uvalue for the flipped material construction is
> significantly higher than for the normal construction, but I believe
> this is not a useful value to understand the e+ calculations, as the
> engine is only concerned about material temperatures and conductivities
> of the layers, right?
>
> ROB - A full window heat balance calculation is performed each time step
> accounting for absorption, reflectance, and transmittance of all layers
> in the window construction. See "Window Heat Balance Calculation" in
> the E+ Engineering Reference.
>
> Hope someone can clear this up.
>
> By the way, there is a slight difference between doing the same
> operation using Window5 data files instead of explicit e+ materials and
> constructions. Is this simply due to the more specific optical data
> provided in the W5 datafile compared to using the "Spectral Average"
> optical data type?
>
> ROB - We are working on correcting some issues related to differences
> between W5 import and window constructions input through the IDF. In
> general, you will always see differences between using full spectral
> data and spectral average data, whether input comes from W5 or directly
> through your IDF.
>
> And lastly, what happens if a different set of materials are used for
> the layers of an adjacent surface? ie, can I use a flipped-face low-E
> glass for one construction, and a non-flipped glass material for the
> reversed construction? No time for more experiments.
>
> ROB - I thought this is exactly what you had done.
>
> r3
>
> [Non-text portions of this message have been removed]
>
>
[Non-text portions of this message have been removed]
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