Re: [GBlist] dual pane glass for 450 f?

[Renewable News Network <rnn@rnn.com>]

Can you run side-by-side tests?

This would be interesting for solar cookers.  A lot depends on the
absorber surfaces, or whatever's happening under the glazings (the
question being:  what's absorbed, what's taken away by a heat transfer
medium, what's reradiated, etc.)  Low/medium temperature flat plate
collectors use single glazing over a selective absorber, as standard
practise, which compares in short term performance with double glass
over non-selective surfaces -- a configuration, which doesn't do the
job for a number of other reasons.

In the higher temperature ranges, there might be an area to explore,
comparing single and double glass, w/ and w/o heat mirror coatings, and
the different spacings.  I'd guess that if the gap were over 2-3 inches,
a conventive loop would build up.

The "low E glazing" thread failed to mention the value in simply feeling
the temperature of the various glazings to sense which ones are working to
hold in the heat.  Argon filled insulated glazing feels warmer to the
touch and its obviously better.  If one cares to speculate on the surface
temmperatures, one could even get a delta T and calculate the performace
in terms of heat transfer.

My sunspace now has a new insulated lite with heat mirror, which is warmer
than an older insulated lite without any coating.  Visually there's no
apparent difference.

What's your application?

Yours truly,
Ross@rnn.com


On Wed, 9 Jan 2002, Y & L wrote:

> Does anyone have an idea...
>
> By how much would the spacing between 2 panes have to be adjusted for
> temperatures between 300f and 450f
>
> if  a) air
> and b) argon  between sheets?
>
>
> Dear listmembers
> >
> >A few years ago there was an discussion regarding glazing
> >
> >"Each gas has an "optimal" cavity spacing,
> >(approx. air 12.7mm, argon  9.52mm and for krypton  6.35mm)
> >beyond which the primary heat
> >transfer mechanism switches from conduction to convection. However,  the
> >TOTAL R-value remains constant beyond the "optimal" spacing, as the
> >increased heat losses from convection are offset by decreased heat losses
> >from conduction. "
> >
> >I presume the above was for double glazing only?
> >What is the situation with extra clear (low iron) glass and/or low
> >emmissitivite coated glass?
> >
> >What is the situation with triple glazing ? For example some data from
> >manufacturers where the spacing increases :
> >
> >Triple glazed krypton gas filled, low e coat on suface 2 et 5 calculated
> >DIN 52619 (German standard)
> >4/8/4/8/4 mm      0.7 W/m2K u value
> >4/10/4/10/4 mm   0.6 W/m2K u value
> >4/12/4/12/4 mm   0.5 W/m2K u value
> >
> >Are there any detailed technical papers on this subject available via the
> >internet?
> >
>
>
>
>
>
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______________________________________________________________________
This greenbuilding dialogue is sponsored by REPP/CREST, creator of
Solstice http://www.crest.org, and BuildingGreen, Inc., publisher of
Environmental Building News and GreenSpec http://www.BuildingGreen.com
______________________________________________________________________